Last update: November 2, 2022

Identify and Treat Columnaris (Saddle Back Disease)

Oh, no!

Does your fish have discolored white patches on his scales?

It might just be columnaris.

Today, I am going to teach you everything you need to know about columnaris – including how to identify and treat it.

This guide might just save the life of your fish.

What is columnaris?

There is a lot of misinformation about this disease, even on sites like Wikipedia. So, let’s straighten some of this out.

Bacteria causes columnaris – Flavobacterium columnare to be exact. Don’t worry, no need to remember this name! Everyone in fishkeeping either refers to it as columnaris or, less commonly, Saddleback disease.

Columnaris bacteria are small. Real small. So small that you need a microscope to see them. Here is the gill of a rainbow trout infected with columnaris…

Columnaris bacteria viewed under an electron microscope on gill of rainbow trout fish
© 2013 BioMed Central Ltd. CC2.0

As you see, when viewed under a microscope, the bacteria resemble rods or columns– yep, that’s how this bacteria got its name.

Columnaris only affects freshwater fish, both in the wild and in aquariums. It cannot live in aquarium salt water.[1]

Any species of freshwater fish can come down with a columnaris fungal infection.

Columnaris is very dangerous and will kill your fish if left untreated.

In fact, a columnaris bacterial infection can kill your fish rapidly – sometimes it only takes a day or two from the first sign.

If your fish’s outward symptoms match that of columnaris, then you need to start antibiotic treatment right away.

Columnaris is also very contagious between fish. If one comes down with it, then all the other fish in your tank are also at risk.

Fortunately, humans are not affected by columnaris. You and your family will not get sick from an infected fish.

How does columnaris get inside your aquarium?

Here’s the interesting thing about columnaris:

It’s already inside your aquarium!

Yep, it’s just hanging around, waiting to strike. In fact, columnaris exists in every freshwater aquatic system – everything from small betta tanks to large-scale commercial operations have columnaris in the water.

In fact, columnaris is a huge concern for commercial fisheries since it is highly contagious and can wipe out large numbers of fish very quickly.[2]

However, as explained later in this guide, even though columnaris is present in every aquarium, it is only a threat to your fish in very specific, and preventable, circumstances.

How do you identify columnaris? (Symptoms)

Columnaris is quite difficult to identify and is often confused with fungal diseases such as cotton wool disease or cotton mouth disease. Straight up, if you see little tufts of cottony stuff that resemble white-colored bread mold, it isn’t columnaris.

What makes columnaris so darn hard to identify is that its appearance varies dramatically according to how far along the disease is. To add to the confusion, different strains look and act differently from each other.

To keep things simple, Columnaris strains generally fall into one of two categories, fast or slow. The fast columnaris can kill your fish within 24 hours. In most cases, your fish will be dead long before you even notice any outward symptoms.

If your fish is still alive and shows the following symptoms, then you are dealing with a slow strain of columnaris – it’s still deadly, but you should be able to treat it if you catch it quickly.

Close-up on columnaris on scales of fish

Generally, columnaris starts out looking like bleached or off-color patches on the body of your fish. As the infection grows, the surrounding scales also begin to look washed out.

The exact color of the infection varies based on the color of your fish and how far along the disease is. While it’s most commonly identified when white, it can also look yellow or even orange.

It’s important to note that these discolored patches will be flat – not bumpy or fluffy.

As the infection continues, it can completely eat away at the scales and skin of your fish. At this point, the skin splits, and the scales turn white and flake off. The bacterial fish disease can also form long filaments that are visible to the naked eye. It’s this stage where the columnaris disease is usually misidentified as a fish fungus.

Neon tetra with columnaris

As the bacteria continues to eat through the skin of your fish, it reveals the muscles underneath, looking bright red and bloody. If left untreated, columnaris will eat a hole in your fish.

Gourami fish with columnaris infection eating away scales and skin to reveal bloody muscle

This can happen anywhere on the body of your fish…

Columnaris infection eating away at gills of fish bloody red muscle

Less commonly, the infection shows up as a distinctive round patch behind the dorsal fin of your fish. It kind of looks like your fish is wearing a small horse saddle – this is why you sometimes hear columnaris referred to as Saddleback disease.

Boseman's rainbowfish with columnaris Saddleback disease on scales

Columnaris can also start as a mouth infection.

When this happens, your fish’s mouth looks bleached, like it’s wearing lipstick.

Black betta infected with columnaris mouth infection in aquarium

As the mouth infection continues, the columnaris eats away at the skin inside and outside the mouth, causing it to flake and become puffy. This is often misidentified as a mouth fungus infection when it’s actually columnaris.

Black Betta infected with columnaris of the mouth side photo

Columnaris can also take a foothold in the gills, making them look bloody as it eats away on the inside.

Unfortunately, columnaris of the gills is almost impossible to identify while the fish is inside your tank water. Most people only recognize columnaris of the gills after their fish dies. Instead, you need to look for other outward symptoms that provide clues to look closer at the gills of your fish…

As columnaris eats away at your fish’s gills, breathing becomes more difficult. As a result, your fish’s gills will move much faster than normal as he tries harder to breathe.

You may even notice your fish move to the top of your entire tank where there is more oxygen or even gasp for air at the surface of the tank water.

Fish suffering from columnaris are often less active and may not eat well or refuse to eat altogether. It’s worth mentioning that lack of energy and refusing to eat are common symptom of many aquarium diseases and, on their own, do not mean that your fish has columnaris.

Scratching is the final clue that your fish has a columnaris infection – columnaris can be itchy. Since your fish doesn’t have hands, he will swim close to objects and brush against them in an effort to make the itching stop. This can result in scrapes and worn down skin, exposing muscle and flesh.

As the columnaris progresses, you may notice that your fish’s fins look bleached out, ragged or even completely worn away. This is commonly referred to as fin rot.

Not all fish with columnaris develop fin rot. In many cases, it’s a secondary infection, which brings me to my next point…

Your fish can catch more than one disease at a time. In fact, by coming down with columnaris, your fish is actually more likely to be afflicted with another disease.[3]

Because your fish is already weak from both stress and columnaris, your fish is more likely to catch other diseases than he normally would.

For example, this platy is suffering from both columnaris and Ich…

Platy with a couple of white spots from Ich and columnaris secondary infection

A second disease caught after the first is referred to as a secondary infection.

This is why identifying any fish disease can be difficult – your fish may actually be battling two diseases at the same time while you are trying to determine a single disease.

While any aquarium fish can come down with columnaris, certain fish are more prone to it. This is a particular problem with fish bred in huge numbers, such as betta, with weak genetics. Livebearers like guppies, Endlers and platies are prone to columnaris as well.

How do you treat columnaris?

Have you diagnosed your fish with columnaris?

Well, the next step is getting rid of it.

Important: Your fish might already be too weak or too far gone to be saved. While I cannot guarantee the survival of your fish, using these steps gives your finned friend the best shot of overcoming columnaris.

Incorrectly treating columnaris can harm or even kill your fish. That’s the opposite of what we are going for, right? So, carefully read each step before taking action!

Step 1. Quarantine

Ideally, you want to place any fish showing symptoms of columnaris into a separate hospital tank.

This helps in several ways:

The most obvious advantage of a hospital tank is that it prevents the columnaris infection from spreading to other fish.

Second, it stops your sick fish from being bullied by healthy tank mates. For their own safety, healthy fish often instinctively drive off a sick fish. In an aquarium, however, the sick fish has nowhere to go, and this bullying will only stress the fish out further.

Next, medicine is dosed according to the amount of alkaline water in your tank. If your hospital tank is smaller than your main aquarium, then you won’t need as much medication. Medicine can be expensive and treating a 10-gallon hospital tank versus a 30-gallon of water one can result in big savings.

Finally, medication can stress healthy fish. Some can even kill the beneficial bacteria inside your filter. As a result, only use treatments when dealing with a harsh disease like columnaris. By only treating your sick fish, your remaining fish won’t be exposed to heavy medications.

Step 2. Check your water quality

Using an aquarium test kit to make sure water quality is good when treating columnaris

As with any disease, to see the best results when fighting columnaris, you want the water in your tank to be pristine.

You should already be regularly testing your water with a good aquarium test kit. If you aren’t, now is the perfect time to start.

So, grab a test kit and check the following:

Not only will good water quality allow your fish to recover faster, but it can also impact how certain columnaris medications affect your fish.[4]

If anything looks out of the ordinary, fix it before moving forward with the columnaris treatment.

Step 3. Turn down the heat

Columnaris loves the heat.[5] The warmer the water, the faster columnaris spreads.

Ideally, you don’t want the temperature to exceed 75°F (23.9°C). If your temperature exceeds 75˚F, then you want to decrease it to slow down the spread of columnaris – doing so gives your fish the greatest chance of survival.

Now, the trick to lowering the water temperature is to do it slooooooooowly.

You see, fish are sensitive to rapid changes in temperature. If you lower it too quickly, you risk killing your fish. For more info, check out our guide to aquarium temperature.

So, instead of adjusting the water to the lowest temperature your fish will tolerate, decrease it by 2˚F (1˚C) every hour until you reach the desired temperature.

When doing this, regularly test the temperature with a good aquarium thermometer to make sure it is still in your fish’s comfort zone.

It’s important that you only adjust it to a temperature that is as low as they will tolerate. Research to find the preferred temperature for your fish. Those with community tanks, meaning with multiple types of fish, need to find the sweet spot where they are all comfortable.

Step 4. Dose your columnaris medicine

FishLab Note: Before adding columnaris medicine to your tank, remove any chemical filter media such as activated carbon or Purigen. These can soak up certain types of medication, preventing it from treating your fish.

Many expert fish keepers recommend a combination of nitrofurazone and kanamycin as the best treatment for an outbreak of columnaris. And, I agree. I have used this treatment on more than one occasion to successfully cure my fish of columnaris.

In my opinion, this treatment gives your fish the best chance of survival. Using one or the other does not seem to have the same success rate – so use them together.

First, you need to grab medicine with nitrofurazone as the active ingredient. I personally use this one…

API Furan-2 a nitrofurazone treatment for fish with columnaris

Contains10 packets
Dose1 packet per 10 gallons
Full course4 doses

Next, you need a medication that contains kanamycin as the active ingredient. I personally use this one…

Seachem KanaPlex kanamycin treatment for fish with columnaris

Contains27 scoops
Dose1 scoop per 5 gallons
Full course3 doses

Have these two medications? Now, it’s time to dose your fish.

Here is how I dose the two for maximum effectiveness. Add a single dose of medication according to the following schedule, I add an extra course of Furan-2 on day 5.

  • Day 1: Furan-2 and KanaPlex
  • Day 2: Furan-2
  • Day 3: 25% water change, Furan-2 and KanaPlex
  • Day 4: Furan-2
  • Day 5: 25% water change, Furan-2 and KanaPlex

It is worth mentioning that in severe cases, you may need to do back-to-back treatments on your fish, for a total of 10 days. This is a judgment call that only you can make, based on how well your fish has recovered.

This powerful 1-2 punch of medication should be all you need to beat columnaris for good.

How do you prevent columnaris?

Most people believe that columnaris bacteria exist in every aquarium.

So if that’s the case, then why doesn’t every fish become infected?

Well, columnaris often strikes when a fish is stressed and in a weakened state – when your fish’s immune system cannot fight off the disease.

So if you eliminate stress, you make your aquarium columnaris-proof, right?

As if you needed another reason to stop stress, it’s the number one cause of death in fish.

Fortunately, keeping your aquarium stress-free is darn simple. In fact, much of it comes down to good housekeeping – things you should already be doing!

  • Cycling your aquarium
  • Quarantining new fish before adding them to your tank
  • Not overstocking your tank
  • Stocking compatible fish and invertebrates
  • Testing your water quality
  • Keeping water parameters stable
  • Cleaning and maintaining your aquarium
  • Performing water changes
  • Not overfeeding your fish (and feeding a balanced diet)

Not too hard, right? These simple tasks keep your fish happy, healthy and safe from most aquarium diseases.

For those of you with hard water, there is one additional step you can take to prevent columnaris…

Reduce the general hardness (GH) of your aquarium.

Several studies show that reducing the GH of your water makes it harder for fish to develop a columnaris infection.[6] [7]

To put it simply, the theory is that bacteria cannot attach themselves to fish effectively in less hard water.

For more information, check out our GH guide. It covers everything you need to know about the importance of GH and how to balance it.


As you see, columnaris is one of the nastier aquarium diseases.

But if you catch it early and with proper treatment (and a bit of luck), your fish will beat columnaris for good.

A sad fact of columnaris is that even if you do everything correctly, your betta fish still might not make it – perhaps you caught it too late, or it’s a fast strain.

If your fish doesn’t make it, don’t beat yourself up. Go through our preventative steps so that you don’t face the same problem in the future.

I would also add that if it’s too late for treatment, you may have no other solution than to euthanize your fish. I know it can be hard, but it may be the only way to stop your fish from suffering.

How do you treat a columnaris infestation? Let me know in the comments below!

Comments (114)

Hi again ..
I wish i had read your blogs 2 weeks ago. I lost 20 of my female bettas because of this. But i dint know how to treat them. After that i dried my whole aquarium and its decorations in sunlight for a day and again filled well water and added 7 females more. Now 2 are stressed and looks like they developed dropsy(raised scales)moved them to a seperate small tank. If you mail me back i would like to share some of pics of my old bettas and would like to know was it the same or other. So that i can be ready further.

Hi Tauseef,

Unfortunately, outside of comments relating to my articles, I do not give individual advice. It’s a stance I have had to take, before I was spending 3 hours of my day answering individual questions, and that’s when my site was considerably smaller. Unfortunately, as much as I want to help everyone, as a single person, I just don’t have the time. I barely have enough time to work on new articles for this site as it is. I suggest joining a forum, plenty of fish keepers will be able to help you.

Yeah, there are tons of online forums and fish groups on facebook. I suggest doing some online research. You really shouldnt just add fish to a tank. It needs to be cycled properly first. So hop on over to google or facebook and get started. Theres a ton of great info and ppl happy to look at your photos and give you some help.

Hi, thank you so very much for this article. I have done back to back doses of the Kanaplex/Furan-2, but I am still seeing some of the white film on my Rasboras. Should I risk a 3rd full treatment or just try the Furan for a 3rd round?

Hi Jodi,

Assuming it is columnaris, have you been noticing improvement since you started medicating, did the disease respond to this treatment? Also, is the white film damaged skin or does it look like the disease you have been fighting? If it is columnaris your fish must have had a severe case, all instances I have observed have cleared in two rounds and the ones that didn’t, the fish was too far gone to save. That isn’t to say that what you are dealing with isn’t columnaris.

If you suspect it’s a columnaris infection, and you noticed that treatment has been working so far, it makes sense to continue dosing. However, this is a decision that only you can make.

Hi How do I medicate tetras using kanamycin? Its the only one I could get in Aus.
Do I dose a half dose?

Hi Sarah,

Did you buy it as a fish medication? If so, simply follow the instructions. However, if you can obtain nitrofurazone combining the two together results in a higher rate of success for Columnaris in my experience.

I’ve been told Kanamycin will wreck the kidneys of goldfish. Anyone have experience with using kanamycin on goldfish? Life expectancy of a fish that recovered from Columnaris using kanamycin?

Great and informative article!

What do you look for to determine if the infection is enough to warrant 2 rounds of kanaplex + furan-2 vs 1?

Hi Andrea,

That’s an excellent question. It entirely depends how far along the columnaris infection was before it was treated and if there are any remaining tell-tale signs. To be honest, I have only ever needed a single round of these two treatments, it’s an effective remedy. In all the cases where my fish lived through it, they have made a full recovery. My last experience battling columnaris was years ago. However, after discussing this topic within my local fish club and speaking with other experienced Aquarius, there are times that you may need a double dose – anecdotally, it appears there are different strains, some of which while still responding to the medication do so at a slower rate.

I was wondering if the level of furan-2 in the tank could possibly be harmful to my Betta with this course of treatment? I’ve read how this medication is particularly strong, and how it is a possible carcinogen (which should be written in bigger letters on the box).

Hi Noel,

A lot of chemicals that fall under “medication” are not the best for fish, however, in many cases, it’s trading a certain death sentence from the disease, for the possibly negative effects of the medication.

As for Nitrofurazone being carcinogenic, the last time I read studies, there was inadequate evidence for carcinogenicity in humans. I vaguely recall a study where rats fed nitrofurazone had a higher incidence of cancer, but let’s face it, it’s obviously not designed to be consumed. If there is a new study, I would love to read it.

I’ve been fighting this disease in my tank for about a month.

I have a 29 gallon tank, and I used to do a 5 gallon water change every 7-10 days, and never had any problems.

I suddenly lost three neon tetras and a dwarf guorami over a just a couple of days with white stuff around their mouths, a big red sore on the side of one fish, and one fish lost part of its tail.

So, I started treating the tank with a combination of both Metroplex and Kanoplex every other day, along with a 5 gallon water change, every other day (water was heated to the same temperature, and treated with a chlorine remover/conditioner).

Near the end of that treatment, everything looked better, but then a few days later, one of my fish started having white fuzz around the mouth, and with scales below its mouth looking loose.

Over the last two weeks I’ve been dosing the tank every other day with Melafix, and changing out 5 gallons of water every other day (heated and conditioned water).

The fish perked up, until yesterday (day 10 of the Melafix cycle), and today two of my fish look like their entire lower jaws are missing.


These two fish are so far gone, that I’m wondering if I should euthanize them?

Should I consider sterilizing the entire tank, and starting over with new rocks and everything? I would put the remaining fish in a smaller tank to set up the new one…

Hi Fagan, I’m terribly sorry to hear that things have gone sour in your recovery efforts. Unfortunately, I am not qualified to diagnose fish. However, I will say that if I was in your situation, based on what you have described, I would likely consider euthanization. It’s a judgement call only you can make and not one to be made lightly.

As for sterilizing, It’s a tricky one as this will essentially crash the cycle of your tank. You’ll basically need to cycle any tank you add your fish to all over again. Since you still have fish, you’ll need to perform a fish-in cycle which is stressful and can also kill fish. It’s kinda a lose – lose situation and again, a call only you can make.

Hi Ian,

great job, really useful, practical and solid source of informations about this desease, thank you.



Your citation (under the photo):
„As you see, when viewed under a microscope, the bacteria resemble rods or columns– yep, that’s how this bacteria got its name.“

Here is slightly different and more detailed opinions how this bacteria got its name – its not the shape of solitary bacteria cell, but rather column-like formations of many of them.

„The columnaris bacteria can be differentiated from other bacteria by their size and shape (long, thin rods, 7 to 10 millimeters and approximately 10 to 20 times longer than wide); their movement (flexing and gliding); and the formation of “haystacks” (bacterial cells that form columns on the surface of tissue).“

„With a microscope, scrapings from a columnaris lesion then placed under a microscope will reveal long, thin, rod shaped motile bacteria. The bacterial clumps form microscopic columns or dome shaped masses, hence the name columnaris.“

Would it be advisable to treat the tank even if all the fish are dead and gone? I ask because I lost all my fish quickly and wonder if the bacteria are still present.

Hi Katie,

It entirely depends on whether your fish came down with columnaris or not. There are plenty of diseases that have similar symptoms, some will require you to disinfect your entire tank while others are less of a concern.

Thanks for sharing your knowledge. I have 2 different medicated flake foods, 1 has oxytetracycline, the other, kanamycin. Which one would be more effective?

Hi Steve,

From my understanding, Columnaris is gram negative and oxytetracycline is largely a gram positive treatment, which won’t help treat columnaris. Of the two, Kanamycin would be more effective. However, I still prefer my 1-2 punch method above, which doses the water.

Thank you for the informative post! I have recently been dealing with what I suspect is one of the less aggressive strains of Columnaris and have been treating for an extended period. I had gone through several cycles of various antibiotics, to no avail, before finding this post. The only thing I noticed any improvement from was a week-long salt treatment, which I upped to 3 tsp/gallon over the course of 3 days, but which still did not clear the symptoms. The meds I previously tried had included both kanaplex and furan-2, but I had used each individually per their instructions, unsuccessfully. Those were followed by a full course of sulfaplex, then the salt.

Anyway, I found the above post and decided to give the simultaneous kanaplex/furan-2 treatment a try. I have only the last double dose remaining to go tonight and all affected fish remaining in the tank appear to have been cleared of their symptoms (my remaining poropanchax luxophthalmus lampeyes look all clear, though I lost 2 females to the outbreak), aside from 1 cardinal tetra. This guy actually has some “cotton mouth” still hanging out. His color looks good and he is extremely active, as well as eating. He seems totally fine, aside from his mouth.

My question is, should I try to manually remove it? The lampeyes all just got white lips, aside from one of the lost females whose lips both turned white and looked like they were started to disappear, giving kind of a skeletal look before I lost her. The tetra is the only one who develop this… protrusion, which hangs off of one side of his mouth and doesn’t seem to be going away. I tooks some pics, but I don’t see an option to include them here. Any insight would be appreciated.

Hi Chris,

It’s crazy how often I hear people try both medications independently not achieving the same results. I’m glad to hear using the two together has seen a dramatic improvement in your fish – also, congratulations on your diagnosing skills, it means you successful identified that your fish had columnaris which can be a mission in it’s own right. Congratulations again on successfully treating your fish!

As for your question, Manual removal would be problematic. If it is cotton mouth, the spores left behind will still be present. Malachtite green or salt is generally effective at removing it. Given you have already used a salt treatment, I just want to clarify that you are confident it is cotton mouth disease? Sometimes when the “skin” splits at the mouth, brought on by columnaris, it leaves clear white bits poking out that can sometimes be confused for cotton mouth.

I honestly don’t know. I guess that would make sense. The best way u can describe it would be a whitish or light grey protrusion from one side of the tetra’s mouth. It has not responded to any of the treatments I have attempted, so maybe that’s why. If it is in fact split “skin,” do you think it will just remain the same, or will it eventually fall off? Like I noted before, the fish seems entirely unaffected… active, hungry and fully colored up. His lips are no longer white, either.

It’s hard to say. If I was in your shoes, and had tried treating it with cotton mouth treatments, I would take a “wait and see” approach. Unfortunately, I could only guess as to whether or not this will go away. If it is a physical wound then it will look likely look better over time but will possibly scar.

My pleasure, I hope it’s as I suspect and just a physical wound – it sounds like you have been through enough medication as it is!

Hello, my tank has columnaris and this article has been incredibly valuable, thank you! My question is this: in my country I can only get Furan 2. Nothing ending in -plex at all. It wont even get through customs. So what else can you suggest please? I have Khuli’s in the tank also which makes dosing more difficult. Thank you in advance for your advise.

Hi Xnedranz,

Kanaplex is kanamycin based. Are you able to track any fish medicine containing that down? Unfortunately, I don’t have a whole lot of knowlege outside of the American market.

Is it possible to have bad drug interactions when adding a 3rd medication? My Betta developed ich on top of his Columnaris, and it seemed like the furzan/kanaplex was working miracles, until day 3 when I added ich treatment. He then went downhill over the next 5 days -now essentially blind, can’t see food, gasping for air. (I’m planning to euthanize him tonight.)

Thank you so much for this article. I wish I had found this a month ago, I think it would have saved my Betta. two full courses of erythromycin just didn’t clear his infection, and by the time I found your advice here I think it was too late. I’m going to read everything else on your site before I try this again.

Hi Beth,

Treating multiple diseases at once is a nightmare. I’m sorry to hear you had to go through this. It’s possible that ich treatment was a shock to the system, or perhaps your betta was already far gone and the effects coincidentally aligned with when you added ich medication. Unfortunately, it’s really hard to say.

If you need any pointers or anything explained on the site, please comment that article and I’ll do my best to help. I hope you don’t give up on fish – once you have a handle on what to do, they are wonderful pets!

Thanks so much for the information! It totally saved my oldest bumble bee cichlid when I combined the two medication. Now, dumb question, he has gone through the 5 days of treatment and there are no more visible signs of the disease. When do you suggest I put him back in his normal tank?

Thanks !

Hi Lauren,

I’m really happy to hear you found success and saved your Bumblebee Cichlid – they are beautiful fish!

That’s not a silly question at all! The exact answer will vary according to who you speak to. I generally leave them in the hospital tank for up to another week once I have stopped medicating. This allows me to really closely monitor before returning them to the tank and also minimizes the risk of infecting the other fish, just in case there are still traces of the disease.


I try to do the treatment that you offer for my apistogrammas, but being in France is very complicated to get the 2 products,

I ordered furan 2 in the USA and for kanaplex the seller sent me Neoplex to instead, do you think I can do the treatment you are proposing with furan 2 and Neoplex instead of Kanaplex.

Best regards

Hi Gaël,

If you can’t find those two products, then you would want to find an aquarium medication that contains the same ingredients (kanamycin for Kanaplex + nitrofurazone for furan for the active ingredients) I do not believe Neoplex will yield the same results.

Thank you for your informative post. I noticed that two of my platys were acting strange (lethargic, not eating, hanging out at top of tank). Gradually one of the platys began developing white patches (body, lips). After reading your post, it looks much more like Columnaris than ick. We quarantined the fish and began treating the water with Melafix (treats bacterial infections). We gave this medication for 7 days, and much of the white disappeared. She is now swimming all over the tank but still isn’t eating and has a little bit of white and discoloration.

We also purchased both the Furan and Kanaplex you recommended. Now we have a dilemma. Should we continue with the Melafix for a little longer (even thought the bottle says to stop at 7 days) to make sure the fish is totally healthy, stop giving meds and wait/watch or begin the Furan/Kanaplex combo (using dosage you recommended)?

Also, how long should you wait before placing a recovered fish back into their tank? We don’t want to place her back in the old tank and expose our two babies to illness.

Your advice would be greatly appreciated!


Hi Tina,

Diagnosing fish can be difficult and you will have to make a decision here based on what you believe the disease to be. If you believe that you are dealing with columnaris, then I would ditch the melafix and swap over Furan/Kanaplex if I was in your position.

Unfortunately, even if your treatment successfully removes the outside observable symptoms, if your fish isn’t eating then it’s only a matter of time before he gives up the ghost (generally, most healthy fish can go up to a week without eating). Have you tried using garlic to stimulate your fish into eating?

I personally wait another week or two, just to confirm that the fish has recovered. Depending on the size of your display tank, and it’s decorations/plants, it’s much easier to observe in a hospital tank – plus you won’t have to catch her again if you notice symptoms return.

Hmmm…. I thought I might have finally figured out what was going on with my goldfish here but given the time he’s stayed alive (many months with this) it might not be this. I’m sort of at my wits end- is there any way I could get your thoughts, Ian? No one I’ve consulted at the aquarium stores has a guess at this point and you are the best.

He has one spot, white a appears fluffy in water but flat and slimy when out, and it’s not getting better. I set up a hospital tank; over the weeks I’ve hit him with API’s “General Cure”, “Fungus Cure”, and E.M. Erythromycin”, so we hit fungal, bacterial and parasitic. I’m using salts now too. It doesn’t seem to be changing.

I treated both goldfish (the other one had fin rot) and the 2 loaches (probably overkill) but finally, after sterilizing and cycling the main tank, just put them back in.

Ammonia, nitrites and ph are where they need to be. At this point, I’m just hoping to ID this growth so I know what to do next… if anything. Wish I had a way to upload a photo.

I really, really appreciate any thoughts. This site has saved my butt, down to the little details like getting the right thermometer. Thanks for everything!

Hi Kate,

Is it expanding or growing? Has it been found on other fish? I only ask as if it’s been like this for many months, it may be something that has latched onto your fish and become stuck. What happens if you try pick it off (be very careful here and only do this if you are confident in what you are doing, tweezers and a steady hand are needed) if it can be picked off, wait and see if it returns?

The alternative is that if your fish appears happy, healthy, eating normally and behaving as usual is to just leave it. While it is possible that it’s columnaris, if this has been present for many months, it likely would have claimed your fish by now. If it is columnaris, a kanamycin/nitrofurazone combo will stop it in it’s tracks.

Unfortunately, even if I saw a picture, I’d probably be unable to diagnose it – many aquarium fish diseases look similar and have overlapping symptoms. If your aquarium stores are having trouble (they see *a lot* of diseases) diagnosing it, I don’t think I could do so by sight alone either.

I had a red betta who i first thought had gotten a flesh wound by cutting herself on a jagged resin decoration right next to one of her gills since she was acting normal and still had a good appetite. I took out the decoration, did more frequent water changes and added aquarium salt and catappa leaves to help with tissue healing. But then a week or so later she started laying on the tank floor a lot more breathing rapidly and the wound seemed to be getting fluffy looking. After getting advice from a betta fish keeper forum, i quarantined her (she was sharing a space with 4 cory catfish in a divided tank with another betta on the other side) and started dosing her with kanaplex since she had what i believed to be a fungal infection growing in her wound. She got worse quickly, she didnt have much of an appetite, ate only a little, all she did was lay on floor of the container and her scales seemed to be a little raised when i looked at her from above. I thought it was dropsey at this point, so i ordered some medication for that. She died before i could give her that medication. Does all this seem like it could have been columnaris or something else? I’m pretty confused. And since she was sharing water with other fish, what should i do about them? They all seem to look and act healthy..

Hi April,

Unfortunately, it’s difficult to diagnose online and it could be any number of diseases. It could even have come down to a single unhealthy fish due to the wound. If you other fish are looking and acting fine, I wouldn’t about them at this point.

I have a red male Betta that used to be my sisters. She kept it in atrocious condition and rarely (if ever) changed the water. When I took it from her and cleaned up the tank, the red fish started to turn black around the fins and gills. I’m not sure if this is Columnaris, and I’m a bit afraid to try treatment I’m case it’s not. The fish has been living like this (with the black on the fins/gills) for about 6 months and I only just received it a few weeks ago.
Any advice would be greatly appreciated.

Hi Hannah,

It’s possible it’s ammonia burns, if you grab a master test kit (the API one works best) you’ll have a better idea of what is going on in your tank.

You want to see:

Ammonia = 0
Nitrite = 0
Nitrate = Ideally less than 40

Hello, thanks for the information on how to treat this illness. I have practically no experience with fish, and now my betta looks like he’s sick. I’ve been researching different diseases, and so far columnaris seems to be the best match but I’m not sure. It started off with the scales on his back near his tail turning white and looking like they were flaking off. Now you can see pink flesh peeking out, like the sickness has eaten through to the inside. Does this sound like columnaris to you? As I said, I have no experience with fish and I don’t want to give him the wrong treatment, but I also want to help him get better right away. Thanks for any help you can give me.

Hi Victoria,

Unfortunately, it’s impossible to diagnose fish through comments – I try to avoid it as it’s dangerous giving your fish medication that he doesn’t need.Unfortunately, you’ll have to use the symptoms above to attempt to diagnose it yourself, do more research or speak to a vet.

Hi Ian… I am pretty sure that I have this problem with 2 of my discus fish. what would hbe the minimum temp to drop there water to. as they are normally in 30 degree water all the time. cheers Jess

Hi Jess,

Because all fish are different, you can only lower the temperature to their “comfort zone” You’ll have to research what is the low range for discuss and make sure you don’t drop the temperature lower than that. If you can’t lower it, then just skip that section of the advice.

I had a betta in a community tank who I assume had columnaris. I noticed a white speck on Wednesday that grew double in size Thursday and Friday i put her in a quarentine tank and I dosed Kanaplex then dosed Furan-2 Saturday and went to lunch Sunday and came home to a dead fish. Her mouth was overtaken with the cotton. My question is should I dose the main tank she came from as well. I dont know if it’s my paranoia but my Harlequin Rasboras look slightly duller and all have a spot on top of their head between their eyes that I cant determine if it’s a marking or they are getting sick. All are swimming normal are active and eating daily. Neon Tetras seem normal and my cory catfish also seem normal. Would it hurt to do a round of treatment if none are actually sick?

Hi Miles,

You should avoid treating fish with medication if you can help it, it can cause unnecessary stress which in turn *could* lead to illness. If memory serves correctly, I think Harlequin Rasboras can have markings on top of their heads, you may have to google here to make sure they match your fish. It’s would also be unusual for all fish columnaris in exactly the same spot on top of the head. Unfortunately, this is a judgement call that only you can make using the information you have available.

I am pretty sure I have a tank with a few barbs that show signs on their lips of Columnaris (duck lips), already lost two of them and a several more are showing the beginning signs. I know people say QT the infected fish, but since several are showing signs I think it best to just medicate the main tank to ensure no other fish come down with it. Thoughts?

Hi Brenda,

This is entirely a judgement call on your part. You can nuke the entire tank or quarantine. My personal preference is to go the QT route, since I try to avoid exposing healthy fish to medication, but either route will work. You know your fish and your tank best.

Hi Ian!
OK, I’m pretty sure our new rescued betta has this. A couple of days ago he suddenly started acting “dejected” — just hiding, staying completely still on the floor, just darting occasionally to the surface etc — when usually he’s really active and friendly. We fasted him in case it was swim bladder, but of course no change, and then yesterday afternoon we noticed a sort of mooshy light patch on the side of his mouth. That’s the only visible patch; he doesn’t have the saddleback stuff or anywhere on his body, but I think it’s cotton mouth/columnaris yes? So we did a 25% WC and dosed with Kanaplex. THEN I saw your article and your routine with Furan. So my question is, since we started Day 1 yesterday with just the Kanaplex, should we just carry on with Day 2 with the Furan and continue the rest of the routine as described? OR shall we just go this round with Kanaplex only? Also, I’m presuming the med administration should be at about the same time each day (like with human antibiotics) yes? Please let me know as soon as you can, thanks soo much <3

Hi again Ian,
So ok, since it’s coming up to 24 hours since the first Kanaplex dose, and I haven’t heard back from you yet, shall we just go the Kanaplex-route this week and see how that goes? So the second Kanaplex dose will be tomorrow. Or.. ?

He was a very tiny touch perkier today, but really spent most of the day just staying still on the floor. That patch is still just there and nowhere else on him (visibly at any rate). Let me know your thoughts when you can please, thanks!!

Hi Catherine,

Sorry about the delayed reply, I typically only answer comments once a day now since life has gotten so busy.

If you believe it is fungal and not columnaris, then just the Kanaplex alone should do it. If you think it’s columnaris, then the more potent 1-2 punch of Kanaplex and Furan would be needed to confidently eradicate it. Unfortunately, it’s difficult to diagnose fish online and I couldn’t quite say which it is – you’ll need to use your best judgement here with the information available.

If your fish will eat, then yes, feed as usual.

Hi Ian,
I understand, no worries, thank you so much.
Well today I think he has dropsy. The thingie at his mouth area is still there, but neither bigger nor smaller, nor anywhere else. However, today he definitely does have the dreaded pinecone look. I guess we’ll just continue with the Kanaplex alone for now, plus prayers! (p.s. if you don’t mind answering this, feeding while having dropsy is ok yes? thanks!)

I Hope it’s not dropsy, it’s a difficult one that not many fish come back from. While I have seen other fishkeepers beat it, Both times I battled it, my fish passed. My understanding is that you continue to feed as usual. Wishing you all the best here.

Sigh I’m pretty sure it is.. scales pineconing.. slight bloating.. we’ll see. This rescuing thing can actually be quite heartbreaking 🙁 Thanks so much again Ian.

I can imagine. I’m not sure I would have it in me to rescue fish – they just don’t bounce back as well from bad conditions as a dog or cat would. I truly admire you for doing what you do.

Oh I’d missed your reply; thanks so much Ian.

I came on to ask if you knew how long columnaris survives in the tank if it’s empty — as in the fish has been moved to a QT. Could we keep dosing the empty tank with meds for say a week or two? We’d be sorry if the filters are gone cases 🙁

Hi Catherine,

Columnaris is a tricky it’s a little unknown as to what the cause is. The current theory is that it’s always in the tank and attacks fish that are stressed or weak. If you can get your fish recovered and healthy, then columnaris shouldn’t affect them. Of course, there could be different strains or similar types of diseases that are misidentified, which make management harder again. With your fish out of the tank, I’d continue dosing for a few more days at most if it puts your mind at ease, assuming it is columnaris you identified.

hi you say that Columnaris cant live in salt water. i have African cichlid that can tolerate certain amount of salt. will it help to add salt to my aquarium.

Hi Moe,

If your fish don’t have it, it’s probably best not to add preventative measures.

Hi Ian,

I found your article on how to humanely kill your fish and have just put my beautiful betta down.
The tank was fine one day and then had a fungus growth in it the next day (I’m in Australia and the weather has been crazy hot, humid then cold), so I did a water change and checked with the pet shop about how to look after the water in this weather but the damage was already done to my fish. After the water change he just deteriorated so I googled fish euthanasia and found your article. Thank you for the advice, it worked quickly and he is now RIP.
Kind regards,

Hi Toni,

I’m so sorry to hear about your loss. Tanks can be difficult to maintain in fluctuating temperatures. I hope that this experience doesn’t put you off the hobby.

Wishing you all the best!

Hi Ian I have 4 rummy nose tetras. A few of them have developed white lips, or had them prior to me inheriting them. Some of their lips are more white than others But they are all active and eating well and their color is good. Water is good with 0 amm, 0 nitrite and about 10 nitrates. I was under the impression rummy nose are full red in the front? And they usually have weaker color if they’re sick? But I’m worried this is columnaris

Hi Thant,

It’s really hard to say if it may have been there before you inherited them. If the lips are not flaking/fungusy then it may just be their specific markings.

Does adding a submersible UV filter and CO2 injection stimulate the spread of columnaris? I have 7x female bettas dead in the span of less than 5days with all of them showing the symptoms described on the article. They lived peacefully for almost 2 months until I added a UV filter and injected CO2. After less than a week of adding these contraptions I saw the first dead betta. Everything snowballed afterwards with totall of 7x betta, 2x neon tera, and 1x molly dead.

Hi Christopher,

Neither of these additions should have any impact on columnaris. It’s possible something else is amiss here.


I was initially thinking that maybe adding the CO2 disrupted my tanks oxygen availability to my fishes which in turn made the bettas susceptible to the disease. Also there’s a blue indicator light on my UV filter which I crazily theorized to be the UV light giving my bettas some form of cancer.

How come only my bettas are affected the most? 7x already died and I just quarantined 3x more with signs. I will try the medication you suggested but I doubt if they would still be alive by the time I get them. The same aquarium has like 20x glofish tetras and they look very healthy and active.

Thanks for this extremely wonderful article… this should have been my first sentence.. . I apologize. I probably would have disposed my UV filter and CO2 setup had I not read it.

All good, lets start at the beginning, I am doubtful the co2 injection or the UV sterilizer are at fault. When fish experience stress, it can be day or even months before sickness occurs. Unfortunately, this often makes it difficult to pinpoint the exact cause of illness. This can lead people to think it was the last thing added to the tank when it’s very possible this has been an ongoing issue that has only just become apparent. It’s very possible that columnaris is not the cause.

What is your:



Thanks for the response. These are the parameters I measured today (one week after my last water change).

Ammonia: 0ppm
Nitrite: 0ppm
Nitrate: 10ppm-20ppm
PH: 7.8
KH: 9drops from API test (don’t know how to interpret this yet. first time using it today)
GH: 17drops from API test (don’t know how to interpret this yet. first time using it today)

On my last water change (that was when I first discovered the first wave of deaths for my bettas), the parameters were:

Ammonia: 0ppm
Nitrite: 0ppm
PH: 7.5

My aqurium size is 75G and here is the breakdown of the fishes (a snapshot from last week when the disease was first observed until today when some action items were taken):

Glofish tetra: 29x
Zebra: 10x
Mollies: 5x
Cory Catfish: 3x
Plecos: 2x
Nerrite Snails: 5x-10x
Swordtail: 1x

Balloon Swordtail: 9x (3x died from the disease. 6x rellocated to hospital tank just today)
Female Betta: 14x (13x died from the disease. 1x rellocated to a different aquarium last week)
Neon Tetra: 40x (5x missing. 7x died from disease. 28x rellocated to hospital tank just today)

Aqurium is heavily planted with various plants. CO2 was only introduced the past 2 weeks and Flourish Excel was dosed every now and then (no pattern).

I clean the aquarium once a week and the water parameters are almost always the same as described above. I replace around 50% to 75% of the water.

I am about to do another water change today (and will remeasure the parameters afterwards). I am going to replace 75% of the water. I am going to separate some plants that are affected by staghorn algae and treat them separately.

Thinking about it, the other major change I did was to add 20x neon tetra to my aquarium without doing a quarantine. Before this, there was no major activity for a couple of weeks. I am hypothesizing now that the sickness may have been carried by these neon tetras.

Now that my neon tetras are rellocated, I am going to do your recommended treatment for columnaris. I have the medications at hand. I will keep you posted on the progress.

Thanks once again for maintaining a very informative website. I was so amazed that all the issues I am facing are described in detail on this website. After I am done with this columnaris issue, I will go and focus on eliminating algae on my aquarium.

Thanks for the detailed write up, it’s a lot to take in but you seem to be on top of things by the detailed records you keep.

The stand out was that is a lot of fish if they were all in a 75g, especially if those are common plecos. It is possible that overstocking contributed to this mass die-off. Check out for suggested stocking, it’s definitely not perfect, but it’s more accurate than using the “1 inch per gallon” rule.

So to confirm, all these fish that died showed symptoms of columnaris? Or just the fish that were relocated to the hospital tank?

Thanks for the kind words, the site is very incomplete compared to my actual goals for it but family, work, life and of course, my fish, keep getting in the way. I do hope to make it a complete resource one day!


All the fishes that died (mostly bettas) show signs of columnaris consistent of your description of the disease. The fishes that were relocated appear to show something which I just assumed to be columnaris. However since neon tetras are very small, it is hard to tell for sure. I am now on day 3 of the treatment.

With regards to overstocking, I think that’s what happened. I tried to cheat into thinking that most of the fishes are small to fit on the “1 inch per gallon rule” and I kept on adding for the fun of seeing more fishes. My two plecos are common plecos that are 1 1/2 inches long for now.

Bottom line I will change this mentality and reduce the fish count on my 75G aquarium.

Thanks for the advice.

Just another quick thought I had, betta prefer very still water. If you had current, there is the possibility that they became stressed and this contributed to them contracting the disease.

It’s a common mistake when begining, fish tanks hold a lot less fish than we think. Common pleco are very messy fish and grow fast – they can reach up to a foot in length! In ideal conditions, you might only stock two in a 60 gallon. Throw in all those other fish and things would have been pretty rough in there.

I hope as many fish make it as possible. Just be mindful that some of your fish are schooling fish, like your cories. If too many die, you may need to re-stock their number.

It sounds like you learned this stocking lesson the hard way, and it’s not going to be easy if you keep losing fish. But rest assured, a properly stocked tank is quite easy to maintain.

Wishing you all the best!

Hi. Could you please advise me. I just had a very nasty case of Columnaris in my community tank after adding a pleco that I didn’t quarantine for long enough.
I lost 2/3rds of my fish in 48 hrs. I didn’t use any treatment as by the time I realised what it was, it was too late and also the meds recommended aren’t easily available to me. At least not for several weeks as that’s how long they would take to get here.
Thankfully, the outbreak seems over or has at least slowed. No deaths for 4 days now. I have purchased a new tank and plan to move the survivors there but my question is does the bacteria live in the filter? Can I give it all a good clean out and continue to use it? Should I clean the housing and throw away the media? Or should I just throw the whole thing with everything else? Cycling a new filter will obviously endanger my survivors once more and I feel like they’ve been through enough.
Many thanks.

Hi Tammy,

You are spot on with your thoughts of cycling a new filter. If I was in your shoes I would clean the filter housing but keep the filter media where the beneficial bacteria lives. I’m not entirely convinced what you experienced was columnaris, but diagnosing online after the fact is a near impossible task. If your fish have lasted 4 days without complications, and look/behave/eat as normal, then I you may not have to move tanks at all. However, this is a judgement call on your part.

Hi Ian! Well, once again I need your advice. I ordered 6 guppies online from another state. A risk, I know, but I’m not finding the strains I want locally. Five were dead when I opened the box and the remaining one just didn’t look good. I put her in a 5G alone. Her gills had a shiny white outline. She’s a platinum albino so I wasn’t sure if this was normal for this fish, but I wasn’t feeling good about it. No fuzz, no white spots, just a white, shiny, raised white strip outlining both gills. I didn’t think it was a fungus or ich, but I started treating with maracyn and Ich-X. Not eating well. Yesterday the white was gone and in its place it was raw and red. I came here to see if I could find anything and after reading this, it sounds like Columnaris to me. I tried to get kanaplex and Furan-2 – None of the local stores have it in stock. Amazon is backordered until 12/20. I found some on eBay but it won’t get here until 11/27. That’s the best I could do. She may be dead by then. I hate doing just nothing. Should I continue with maracyn and Ich-X? I also have API general cure, maracyn-2, focus, teatree oil, Fish vitamins and garlic. I was thinking of soaking some frozen bloodworms with a piece of garlic hoping she might eat. I also have aquarium salt but I was afraid that might sting on such a raw spot. A) does it sound like Columnaris; and B) what would you suggest until the proper meds arrive? I’ve ordered fish online before, and yes, it’s risky, and while some fish arrive healthy, some sellers are a true disappointment. You’d like to think they all take care of their fish the way they should, but they don’t. I wish the local stores had a better selection. Do you believe in dosing new arrivals with Ich-X and an antibiotic as a precautionary measure?

Hi Deborah,

Unfortunately, given that the other fish were dead on arrival, it’s hard to know what is at play here. Maybe it was poor packing or rough transit. Maybe this one was a survivor but whatever hit the others is biding it’s time and it’s days are numbered despite your best efforts. Because columnaris has so many symptoms, it would be near impossible to confirm if this is what has struck your new fish, it could be anything from ammonia burns to columnaris. Testing the water that the fish were shipped in can sometimes provide clues, such as elevated ammonia. However, it’s probably too late for that. If your fish won’t eat, then it’s only a matter of time before it passes, so I certainly recommend bloodworms and garlic. You can make a medicated food mix by soaking it in garlic and Kanaplex. Columnaris is gram-negative, which macaryn 2 treats and out of your medications is probably the pick if you think it is columnaris. I’d probably stop the ich-x based on what you have said.

I order my new fish through my local fish store which I have trusted for years. They treat all fish prior to stocking their tanks with ich-x and another medication that I currently can’t think for the life of me what it is (my old memory isn’t what it used to be). I still put all fish in a hospital tank and treat with ich-x and monitor them for a week before adding them to my display tank.

Have you spoken to your local fish store (not a pet store like petsmart or petco) about ordering breeds you want? They can often order in plenty of fish that are not on display through their supply channels. It’s less of a gamble than blindly ordering online.

Thanks, Ian. Have I told you how much I appreciate you and the time you take to put this site together and answer our questions? Words like “thank you” just don’t seem to be enough for all that you do.

I do have a local fish guy who quarantines his fish and plants before putting them up for sale. You should see his betta setup! Each betta is it a small tank (no cup), with substrate, a plant, heat, and filtration. It’s not individual of course, but an elaborate system that cost quite a bit of money. And his bettas are absolutely gorgeous – colors you never see in petsmart or petco. And his bettas actually swim in their little tanks – they don’t just lay in the bottom looking so very unhappy. Anyway, we have had a discussion about that but he says he has to buy a certain number, he can’t buy just a couple pairs, and I want so many different ones, I don’t think it’s cost effective for him. But I really need to explore that option again, because what I’m doing has been a bust. That’s how I ended up with hydra in my main tank. I just bought a 55G, and obviously I’m nowhere near ready to stock it, but I’m hoping all my issues are resolved and I’ve learned from my mistakes by the time I am ready for the fish. I’ll start using maracyn two today. Thanks so much.

My pleasure, I’m happy to help. It sounds like you have a fantastic local aquarium, by the sounds of the betta setup. I know I shouldn’t encourage the practice by purchasing from them, but I do buy my betta from Petsmart – they are so pale and discolored that it’s rewarding watching them turn around, regrow their fins and exhibit bright colors and quirky personalities, if you can say fish have personalities.

I’m excited you have a 55g, and I’m sure you are going to nail it when it comes to stocking and care!

I have never had an issue with aquaticarts when it comes to ordering fish online. However, it has been a while since I placed my last order. If I order online, I try to do it in fall/spring since the weather is typically less harsh, which can make all the difference depending on the state you live in.

I have to admit my 2 bettas are from petsmart! They looked so unhappy and I wanted to liberate them from the bland cups! They have really thrived in their 15G – I have a black divider – with plants, warm water, driftwood – one of them uses the floating plants as a bed – they were so happy they started building bubble nests the very next day! And I do believe they have a personality, and they know me – they come right up to me when I approach the tank – although I do attribute that to the fact I’m their food source. There is one online store who sells nothing but guppies and I do trust him explicitly, but he’s so picky about his stock sometimes it’s weeks before he has any fish available. I’m in New York and I just ordered a pair of albino reds from him – they’re going in their own 5G – not because I’m worried about his fish, I’m worried about mine – and then I’m done because now it’s getting too cold and too risky to ship. His fish typically sell out in a few days he has such an amazing reputation, and very beautiful – and healthy – guppies. I really need to learn how to be not so impatient- especially with this new tank. My lack of patience and my “I want it now” mentality is what caused all these problems. I believe I learned my lesson and I surely do not want to mess up a 55G tank. I also bought another 20G with 2 dividers so I can have 3 more bettas. And now I’m out of room, so 7 tanks is my absolute max. The 3 5G are a quarantine tank, breeding tank and fry tank. The males are going in the 55G (not until everyone is totally disease-free) along with a betta sorority, female guppies will remain in the current 20G. I have to split up the males/females otherwise I’ll have guppies coming outta my ears! Of course, neither of these new tanks will be ready for any fish until roughly February-March. Again, thank you for all your great advice – your website is my new “fish bible”. Have a happy holiday season!

It certainly sounds like you have been bitten by the fishkeeping bug – 7 tanks is a lot. Although, in my opinion, It sounds wonderful. I’d have more, but my wife and I have come to an understanding that I’m not allowed to fill every empty space with a fish tank. In my younger years I could beest be described as a “fish hoarder.”

I’m glad I’m not the only one who buys from petsmart. I agree entirely, it is rewarding giving these jailed fish a second chance at life.

I think you have hit the nail on the head when you have identified that slow and steady is the best way to stock. What is the online store you order from? I would love to check it out.

Hi Ian – the guppy guru is Twin Cities Guppies, run by Keng and Sai Lee in St Paul, Minnesota. They have several videos on YouTube and their own website- obviously. I already have 2 pairs from them – blue tail albino and Santa Dumbo, a multicolored guppy. The female just had a gazillion fry. Female guppies from Twin Cities are almost as colorful as the males. I’m not really into the cobra or mosaic guppies, I prefer the more solid colors – purple Moscow, black Moscow, green Moscow, red albino (isn’t that an oxymoron?). I’ve discovered it’s better to wait – you’re not stocking your tank too fast, Keng’s guppies are always healthy, and he gets the most beautiful guppies. I’m finding that some online guppies are the same strain, they just go by different names, so you end up with the same strain twice, a needless expense. Well, I’ve learned, the hard way, but I’ve learned. BTW, the sick female I have seems to be doing better. I’ve been using maracyn-two, and she’s started eating. Something’s going on in my main tank, but I think it’s resolving. I had an oto with fuzzy cotton on his back, and while I was doing online research, he died. I pulled this worm-like thing out of his back that had a hard shell-like or possibly thorny protrusions on its body, with two on its head, like horns. I was told that was a planarium but I don’t believe that. Then one of my guppies got fuzz on his belly – I started treating with maracyn and Ich-X, the fuzz went away, but the belly is still white. Another oto died and so did 2 guppies but no fuzz or white belly. Now 3 more guppies have white belly. They all act ok, all are eating, and after I added salt, it seemed to help. No more outbreaks. I have 1 oto and now 14 guppies in that 20G tank, so it’s not overstocked. I have another new guppy in quarantine and he’s got this white belly now too. I have separate nets, separate equipment for WC, etc, so there’s no cross contamination. Have you had any experience with this white belly. I thought it was a fungus initially because of the fuzz, but now there’s no fuzz. I’m afraid to put my female back in that tank, hence I no longer have a gazillion fry, just a handful who stay deep in the guppy grass. Any thoughts on this?

Hi Debroah,

My apologies for the delayed reply. Had the extended family over for thanksgiving and it was a full time job hosting them.

Thanks for sharing Twin Cities Guppies, I’ll definitely check them out.

I’m really happy to hear that your fish is on the mend. I have my fingers crossed everything progresses smoothly.

That worm doesn’t sound like planaria. To confirm, I have an article with many pictures here:

To me, based on your description, it sounds like it was an anchor worm (another nasty hitch-hiker.) If you google pictures, you should be able to compare. Although they typically cause redness rather than fuzz.

I’m drawing a blank based on the fuzz description, although you should certainly treat your tank for anchor worms in any case.


I am relatively new to fish keeping (about 2 months) and I am at a loss- hoping your thoughts will help me figure this out.

I have a 20gal community- 1 female crowntail betta, 5 ghost shrimp, 1 blushing tetra, 1 rubberlip pleco, 2 mystery snails, 2 glass catfish….I hadn’t had any signs of disease or infection, have hides and multiple live plants (java fern, moss balls, aponogeton, anubias nana, water wisteria, cryptocorene undulata).

I brought 3 glass catfish home. Almost immediately, 2 of them refused to school with the 3rd. I just thought it was due to stress and a new environment. The next morning, there was a single small white dot on the top of the single catfish. Nothing alarming- didnt look like ick, and was extremely small. Throughout the day, this seemed to grow to a faint white circle (nothing visible on head/gills/mouth) about 1/3 of the way down from the head. Again, I was not overly concerned because the fish was still swimming fine other than not schooling, but this was still well within 24 hours of introduction. At about hour 20, I found the fish laying on the bottom of my tank barely swimming. Immediately I removed him and he died shortly thereafter. It did appear fuzzy and this whole scenario took place in about 24 hours. Based off of the research I tried to do, I figured it was columnaris.
The good news- none of the other fish have seemed to be affected at all thus far.

Of course all of this happened on a national holiday so I couldnt treat for anything even if I had an idea. Today, about 48 plus hours later, I bought erythromycin as it seemed the best option of the limited options available. Upon further research, I guess it treats gram positive vs. Gram negative like columnaris.

I am just at a complete loss as to how to treat my fish that are not showing signs of illness…does this sound like columnaris to you? Based off what I’ve found, I’m not sure if 2 different strains could be present simultaneously? Or could just 1 fish have been affected? I’m just reaching out because I’m truly at a loss as to what to do. I added Indian Almond Leaves and my temp is around 77.

Thank you for reading.

Hi Michelle,

Fish will often bully a sick or injured fish and is a big clue that this disease or illness is fish specific. As to what it is, it’s very difficult to diagnose online, even with seeing pictures as many diseases have overlapping symptoms. The first thing you do should be to isolate the obviously sick fish, to keep your other fish safe and so that you use less medication. However, if this fish was sick before you got it and the signs are just becoming apparent, then it may be too late to save it despite your best efforts.

If you are serious about keeping fish, a hospital tank is essential. You would use this to separate any new fish and monitor them for illness and hitchhikers before adding them to your tank. You would also use this to quarantine sick fish. This way you are not medicating fish that don’t need it (medicating healthy fish can cause stress and lead to it’s own set of problems).

Hi Ian – I’m so sorry to bother you again, I know I ask a lot of questions, but this concerns hospital/quarantine tanks, and I’ll bet I’m not the only newbie with this question. I have 2 5G set up right now, one is a hospital tank, the other a quarantine tank. I made the mistake of getting two pairs of guppies at the same time – one pr from Twin Cities – red albinos (I’m not worried about them); the other from a private breeder online, black and purple Moscow, the male arrived with an anchor worm. When and if the fish in the hospital tank becomes well, do I need to break down that tank, clean it and all equipment really good with vinegar, get new substrate, plants, etc, before I can use it again? Same question for the quarantine tank should I discover any new fish are sick. And do I need to maintain and keep an empty hospital tank up and running “just in case “ so I’m not dealing with an uncycled tank which would just add to the problem? Or could I keep shrimp and snails in a hospital tank without worrying about them getting whatever the fish have? Or does something like stress zyme which says you can use and add fish immediately really work for a new tank? I probably don’t need to have substrate or plants, but I figure the more natural the tank is, the less stressful and more comfortable for the fish, or is that overkill? Thank you, once again.

Hi Deborah,

Never a bother! It sounds like you have a very elaborate hospital tank. My hospital tank is designed around cleaning and while it is kept cycled, it is bare bottomed and only contains a couple of boring ornaments. This way, cleaning isn’t an issue.

How you set up your hospital tank is entirely up to you. Some people keep them up, others keep a second sponge filter in their main tank and use that, setting up a new hospital tank each time. You can do the same for the quarantine tank.

Hi Ian – thanks for the info. It’s not elaborate- it’s overkill! ???? and it’s a lot of work to maintain. No plants or substrate certainly simplifies the cleaning process in hospital/quarantine tanks. All my tanks have extra sponge filters with air stones, so transferring one to a new tank would be an easy thing to do. Thanks once again for your sage advice. You have no idea how helpful you’ve been over the past couple of months. I’m about to do something crazy, and if it works, I’ll share it with you, because then it won’t seem so crazy. Happy New Year, Ian! ????????????

Hi Again Deborah,

I’m glad I can help! It sounds like you are in the perfect position to set up a new tank each time – I’ll wager you won’t miss the extra maintenance of keeping the hospital tank up and running, just in case.

I’m very curious about your idea now. I can’t wait to hear about it. Wishing you and your family all the best for the new year 🙂

Hello Ian and thank you for this article. I saved an EXTREMELY ill fish from an office desk. Initially it looked like body rot/fin rot and I treated 5 days with Maracyn two and provided a heater so he got a tiny bit better; wasn’t floating on his side. Then I read more about this illness and it seems like it may be what’s happening. His gills are really inflamed, he was a rotted mouth(little color) and he is swollen with bloat badly. I am treating with Kanaplex and Furan 2. It’s day four and he is now making it to the bottom of the tank and swimming a bit so def better. He’s eating well also. His gills still look really inflamed. Should he be further along after 4 days? Should I do another 5 days? He might also have parasites…I am not sure what is causing the bloat which again is better. I fasted him for 4 days and now feeding daphnia and freeze dried brine shrimp. How ANYONE had this poor fella on their desk floating in sewage water is beyond me but I would REALLY like to save the poor little betta. Any advice would be much appreciated. Margo

Hi Margo,

Firstly, I’m always happy to hear when people rescue neglected fish. You are so awesome for doing that!

Unfortunately, when left in conditions like this, it’s very possible that he has contracted multiple problems. Based on your description, the bloat is certainly separate from the other issues.

For the gills, it’s possible it was ammonia burns, which are best fixed by keeping water as pristine as possible.

If you don’t have a cycled tank, read this guide and use the water change method:

If everything is looking better, but not mostly resolved, I would continue with a second course if you believe it to be columnaris.

If the bloat is getting better then I would continue as you are doing too.

Please prepare yourself for the fact that even though you are doing everything right, it’s possible that the damage has been done and despite your best efforts, this betta still won’t make it. But I have my fingers crossed that he makes a full recovery!

Thank you for your response. He’s in an uncycled hospital tank I built on the fly and with the treatment can’t do much as far as water changes during treatment but am adding prime and doing my best in between treatments. SO frustrating not knowing what to do as it’s just not clear cut. He has no “saddelback” it’s all just around his mouth and eye. His water was absolutely foul so it could be just a bad bacterial infection around his mouth coupled with ammonia burns I guess. Not sure what to do…uugh. I did buy some clove oil if that’s the only option. He’s eating like a piglet so seems like he’s got some fight left. 🙁

I wish I could help you more but a lot of these things take time to know if they are getting better. Unfortunately, in this time he could go either way. The eating is definitely a good sign though. If you are keeping your water as clean as possible, you are doing all you can while medicating. After the second round of treatment, I’d stop and rely on regular water changes. It’s possible he will come good with pure water. If any symptoms get worse, then medicate according to that individual symptom. I have my fingers crossed that he makes a full recovery!

Hello, i have an Oscar fish which took ill on Sunday and judging by this read I believe it could be columnaris. On Sunday she had raised scales all down her sides with a cotton like look to her slime, almost looked as if someone had taken a scourer to her. Although refusing to eat and the obvious infection, she looked relatively healthy and looked as though she could recover. Quarantined her in a small tank, treated with primafix and Melafix and yesterday she looked worse. Red sores on her sides and fins and lying on the bottom of the tank, breathing and looking around but now isn’t swimming. This morning a similar story, we have ensured the water is pristine with tests and the usual water changes however her eyes now are clouding over and she looks ready to give in to the illness. We have continued treatment with Primafix and Melafix after water changes as suggested on dosage. Appreciate in this state there is very little we can do but any advice to at least try and save her would be greatly appreciated.

Hi Luke,

Unfortunately, it may be a little late for this fish. If it is correctly diagnosed as columnaris it is unfortunate that you went down the primafix/melafix as in my experience they are ineffective against gram negative bacteria like columnaris. From your description, it sounds like there is very little to do and I would suspect that even swapping medications at this stage wouldn’t do much. I know it’s really difficult, but you may need to make a judgement call on whether or not to euthanize.

Can you help with clamp tail on my baby guppys. I have look and look no one can give a straight answer its alway tank water or size or genetic. Ibwould just like to know what one it is. Can you help

Hi Chris,

I’m not going to be much help diagnosing this one since it’s typically a symptom of a disease or stress due to poor water conditions, too much light, etc. Unless it’s a birth flaw, treating the disease or stress often resolves the issue.

Hi Ian Sterling,
I have a problem with Columnaris in my aquarium, the problem concerns only Guppy, other species of fish do not show any problems with Columnaris. The problem appeared after buying a sick Guppi male in the aquarium store. Unfortunately I did not quarantine and I noticed the problem later, when it was too late. In my country Poland, I can’t buy Seachem Kanaplex and Furan-2 anywhere. The composition of these medication is prohibited by the EU. I used Sera Bactoforte medication, according to the manufacturer fighting Columnaris which is composed of: 209.7 mg acryllavin, methylene blue 4.95 mg, 0.6 g phenyl glycol, distilled water make up to 100 ml. Unfortunately, neither in one tank nor in the other nothing changed and the infected guppies fall after a few days. Separating sick fish does nothing, because Columnaris is still in the water. I have the option of using an old, more powerful version of Sera Bactoforte S which contains: Nifurpirinol 27.6 mg, neutral, binding reagent up to 1.0 g. I need to carry out treatment in the general aquarium. In your opinion, after what time will Columnaris die in the absence of any victim? Greetings,

Hi Wojciech,

Columnaris is a tricky one since it’s symptoms are shared with many other diseases. It also appears to kill quicker or slower where the symptoms occur. For instance, if it appears on the gills, then it’s game over very quickly. But I have seen fish with the “saddle” on the back symptom last three weeks from the first observance. Unfortunately, this is very anecdotal since for the most part I rely on other people sharing their experiences here.

Thank you for the quick reply. I understand, so it’s really not known after what time Columnaris dies from missing another victim. However, the fight remains in the general aquarium. Do you think Nifurpirinol 27.6 mg will take care of Columnaris instead of Furanol which I can’t buy anywhere because of the ban on this medicament.

Thank you very much for your reply, I will read a bit and use Nifurpirinoll, that’s all I could buy. I will apply the treatment in the general aquarium to destroy Columnaris completely.

Hi Wojciech,

I’ll be very interested to see if this helps your fish recover. I have my fingers crossed it does the trick!

Quick question: when I start the second 5 days of treatment, do I need to do anything to the water first? Remove the medicine in the tank with carbon? Partial water change?


Hi John,

Excellent question. I probably should have made this more clear. A 25% water change prior to the second treatment is recommended.

Not a problem, John.

I hope your fish is able to pull through this. Columnaris is a nasty disease.

I had a columnaris outbreak in my community tank, (which is stocked with 99% livebearers), in January, killing 28 fish (Platys and Endlers – but most deaths were my Platys) in just FOUR AND A HALF DAYS.
For this outbreak, I treated with Maracyn 2. I lost no more fish after treatment on day 2.
Also, with this outbreak, none of my fish that died, (literally absolutely NONE of them), displayed any physical symptoms, whatsoever. (Diagnosis determination was concluded when the death of fish #13 occurred only 36 hours after #1).
Such a rapid rate of death, it was absolutely the only thing I could find in all my searching.

I am currently on day number 3 of Maracyn 2 treatment, for yet another outbreak (this time, effecting mainly only my endlers)
Have lost 7 so far. But this time they ARE showing physics symptoms (i.e-the whitening of the scales in “patches”, {rapid} deterioration of the fins, one I noticed this morning now has infection in her mouth, and flashing {“scratching”} lots, and LOTS of scratching!)

I’m treating my whole 60 gallon tank (very costly!) but I have the 3 worst in a separate tank.

So my main question, I suppose, is – can I use the medications recommended by you in addition to the current treatment of Maracyn?

Hi Tiffany,

I’m so sorry to hear about your ordeal. That must be incredibly disheartening. Mixing medications is tricky and can often cause more harm than good. If you to shift medications, a 50%+ water change and adding carbon back into the filter for 24 hours would be advised before swapping med treatments.

Also, and I know you probably don’t want to hear it, but if the symptoms have gotten incredibly bad then it’s possible that this late, they might not survive the full treatment. I only say this as medicating larger tanks is very expensive and this money spent may be put to better use If you feel it won’t help them.

Just added a packet in my fish has slight white spots but not puffy just sorta flakey it is an orange fish and the white stuff looks the same color as the fins should I begin treating it or not?

Hi Katie,

Unfortunately, I cannot diagnose your fish online. If you believe it’s columnaris, based on his symptoms, then this is the appropriate treatment. Otherwise, your fish may have another disease.

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