Last update: November 17, 2021

Aquarium Safe Silicone – Best, Safest & Strongest

I think you’ll agree with me when I say:

Silicone sealant is one of the most important parts of an aquarium.

After all, silicone is what holds your aquarium together. Without it, your aquarium is little more than glass panes. Which isn’t really an aquarium at all, right?

Many hobbyists only become aware of just how useful silicone is when their tank begins to leak. Silicone to the rescue! A small dollop is enough to fix any leaky fish tank.

Many hobbyists only become aware of just how useful silicone is when their tank begins to leak. Silicone to the rescue! A small dollop is enough to fix any minor leak.

Others use silicone when they want to glue rocks, plants or other decorations to the glass of their tank. Because silicone dries clear, it’s less noticeable than other adhesives.

As you see, silicone is pretty handy stuff. I always keep a tube on hand in case of an emergency. I highly recommend that you do the same.

But before you run out and grab an unused tube of silicone that has been sitting in your shed for years, there is one thing you should know…

Using the wrong type of silicone in your aquarium can kill your fish!

Yep. It turns out that not all silicone is safe for aquarium use.

But don’t stress! I’m here teach you everything you need to know about choosing the ideal silicone for your aquarium, including which is the best for your tank!

So, read on to learn everything you need to know about aquarium safe silicone.

Is silicone the right adhesive to use on your aquarium?

Man comparing an adhesive to silicone to use on his aquarium

It might surprise you to learn that when it comes to sticking one thing to another, there is a wide range of adhesives available. Super glue, cement and epoxy, to name a few.

But none of them are quite like silicone sealant…

You see, silicone has many benefits that make it a suitable adhesive for aquariums. It’s safe, flexible and can last years without needing to be reapplied.

But what makes silicone particularly useful is that it is one of the few adhesives that clings to glass – you know, the stuff that your aquarium is mostly made of.

However, since we are working in a wet environment, there is one important factor you need to consider…

Unlike super glue, silicone doesn’t bond instantly.

Instead, once applied, it slowly dries. This process is called curing and typically takes around seven days to completely cure.[1]

You’ll know if your silicone is still curing because it will be wet to the touch and often smells like salt-and-vinegar chips.

Unfortunately, silicone will not cure if applied under water. It needs to air dry. Even more importantly: Silicone is not deemed aquarium-safe until it completely cures.

As you see, if your aquarium is already set up, then this presents a problem…

To apply silicone to your tank, you must drain your aquarium. If your tank already contains fish, then this is easier said than done. You must rehome your fish while you wait for the silicone in your tank to cure.

If that sounds like a lot of work, and you don’t need to glue anything to glass, why not check out this aquarium-safe super glue, which can be applied under water and dries quickly!

Otherwise, if you need a long-lasting adhesive for glass, silicone really is the best solution. Once it cures, it lasts years and years without any issues.

Pros of silicone:

  • The most suitable choice for sealing a glass aquarium
  • Water-proof
  • Doesn’t release chemicals once cured
  • Bonds to glass
  • Dries clear
  • Remains flexible after curing
  • Holds under pressure
  • Creates durable bonds
  • Available in multiple colors

Cons of silicone:

  • Generally not suitable for acrylic
  • Needs about 7 days to fully cure
  • Not aquarium-safe until cured
  • Does not cure when wet
  • Cannot be painted

Which silicones are safe for aquarium use?

Hand applying aquarium-safe silicone to the edge of a piece of glass

If you wandered into your local Home Depot, you might have noticed their huge wall of silicone sealant.

It might surprise you to learn that most of the silicone you see is dangerous to your fish.

What you want to look for is 100% silicone. This should be pure silicone without any additives.

Now, I say should because some brands still feature 100% silicone on their label but contain other nasty ingredients such as fungicides.

I have seen generic brands floating around my local hardware store claiming to be 100% silicone that also state they contain additives in the fine print. Fortunately, brand name silicones are well-labeled.

If you see any of the following on your tube of silicone, then it should not be used in your aquarium…

Mildew-Resistant, Mold-Free, Bacteria Protection or Anti-Microbial

Silicones making these claims contain fungicides that may kill not only your beneficial bacteria but also your fish.

You don’t want to cycle your tank all over again, do you?

When in doubt, don’t buy it. I’m going to share my favorite aquarium-safe silicone brands later in this guide.

Also, don’t be lured in by brands advertising waterproof silicone. All silicone is 100% waterproof, even if the label doesn’t say so. If it ain’t waterproof, then it ain’t silicone.

Warning, don’t overpay for silicone!

Over the years, I have used dozens of different silicones. And in all this time, I have learned one important lesson as a tank owner:

Price does not equal quality!

Unless you are building an aquarium, and you need the best and most reliable silicone, there is no point in paying extra for expensive silicone.

The worst offenders are the aquarium brands. Take Aqueon’s Silicone Aquarium Sealant. I have seen this silicone cost as much as $12 at my local fish store. $12 for 3 ounces! That’s highway robbery!

Don’t get me wrong, Aqueon’s silicone does exactly what it claims. And if you want to pay extra for an aquarium brand, then there is nothing wrong with that. But, if you are on a budget, then you will be pleased to know that you can achieve the same quality results with any of my top picks from this guide.

With that out of the way, let’s take a closer at the different silicones that I have used over the years. All these silicones are aquarium-safe, as seen by my happy and healthy fish.

Best aquarium safe silicones

It might surprise you just how much silicone it takes to reseal an old glass aquarium. When you need to use a lot of silicone for your fish tank leaks, caulking tubes are the most cost-effective way to buy it.

Just be mindful that to apply silicone from the tube properly, you need a caulking gun.

I personally use this one – it’s so much better than the cheap caulking guns from Home Depot. It makes it easy to accurately apply silicone without drips. Once you try it, there is no going back.

With that in mind, let’s take a closer look at some of the best-performing silicones around.

Best silicones for building or resealing glass aquariums

If you are building or resealing an aquarium, then you want the strongest, most durable and most reliable silicone around. After all, if the silicone used to glue the joints of your aquarium fails, tens or even hundreds of gallons of water are going to flood your home – killing your fish and leaving you with one heck of a mess to clean up.

And when it comes to reliability, two silicones stand out. These silicones are used for their adhesive properties – gluing together tank glass.

If you speak to a professional aquarium builder, chances are that they use one of these two silicones…

1. Momentive RTV100 SeriesMomentive RTV100 Silicone - best for building and resealing aquariums

Most professional fish tank builders I spoke with swear by this product, and if there is anyone who relies on a strong silicone seal, it’s these guys. After all, if you build aquariums for other people, then your reputation is on the line. You want to be confident that the silicone used is going to hold strong for years on the glass surface.[1]

Last year, I made the switch to Momentive for my last reseal, and it’s still holding up well.

Note: If you want this silicone in black, then grab the Momentive RTV103.

2. GE SCS1200

GE SCS1200 Construction Silicone best for resealing and building aquariums

On paper, SCS1200 is the stronger and more durable silicone of the two.[1] Despite this, based on the aquarium suppliers I spoke to, Momentive appears to be the more popular silicone.

This is the silicone that I previously used when building glass tanks before deciding to see what all the fuss was about with Momentive. Based on my experience, both seal well for your typical tank build – you will do no wrong with either.

While I wouldn’t go past these two silicones for building aquariums, they are probably overkill for gluing anything that goes inside your tank.

Use one of these instead…

Best general-purpose silicone for bulk gluing

If you want to glue decorations, backgrounds or rocks to the glass of your aquarium (or anywhere else), then these silicones hold strong at an affordable price…

GE Silicone 1 Window and Door – CLEAR SILICONE

GE Silicone 1 Window and Door silicone-safe for aquarium use

This is my go-to silicone for aquarium use. Not only is it affordable, but it can be found almost anywhere from Amazon to your local hardware store or Walmart.

Note: Please do confuse this with GE Silicone 2, which is unsafe for aquarium use.

ASI Aquarium Sealant – BLACK SILICONE

ASI Black Aquarium-Safe Silicone Sealant

Unless I am gluing a decoration to my glass, I typically use black instead of clear. Black silicone hides algae much better than the clear type.

I’m going to be honest with you, ASI is the only black silicone I have ever used, but it holds strong, is aquarium-safe and relatively affordable.

Best silicone for precise gluing

You know the problem with caulking guns? They can be difficult to control. If you are working on a delicate decoration and only need to administer a small amount of silicone, then one of these tiny tubes is your best bet.

Sure, they might not offer the same value for the money as a caulking tube, but if you only need a small amount of silicone, then most of that big tube will be wasted anyway.

Loctite Aquarium-Safe Clear Silicone

Cheap and aquarium-safe – a great mix. This small tube of silicone is the perfect size to keep in your aquarium cabinet, just in case you experience any emergency leaks.

Aqueon Black Silicone Aquarium Sealant

I know I gave Aqueon a hard time earlier for making expensive silicone sealant, but they are one of very few brands that offers black aquarium-safe silicone in a small tube.


The best and safest aquarium silicone:

Brand For
Momentive RTV Series Sealing Aquariums
GE SCS1200 Sealing Aquariums
GE Silicone 1 Window and Door Cheap bulk sealing
ASI Aquarium Sealant Bulk sealing, in black
Loctite Clear Silicone Precise sealing
Aqueon black silicone Precision sealing in black

As you see, not all silicones are created equally, so it’s important to choose the ideal one for your aquarium.

To see the best results, clean any area where you will apply silicone. And, as always, follow the directions on the packaging.

Finally, I want to mention that no silicone lasts forever. Over time, silicone will dry, crack and peel. However, this typically takes years.

Seriously! One of my tanks lasted 15 years before it needed resealing. If you choose a good silicone sealant, you’ll see a lot of mileage before it starts to wear.

Ian Sterling

Ian Sterling, founder of, began his aquarium journey over 30 years ago, driven by a deep fascination for fish and their diverse personalities. His website,, is dedicated to making fishkeeping accessible and enjoyable, offering beginner-friendly guidance, expert insights, and a community for aquarists to connect and share experiences.

Comments (72)

I am in the process of build a aquarium I am curious if you have any advice in building on I have watch a lot of videos on YouTube but I just don’t feel comfortable sealing a 120 gallon aquarium with silicone and no bracing. Would the GE SCS1200 hold all the panels together with it filled up with water? Would you advise me to brace it this is my first aquarium build. Thanks for the article it was very informing

Hi Dylan,

It depends on the size of the glass panels and thickness of the glass. If this is the first time you have built a tank and are inexperienced, I would probably brace it. I personally avoid giving advice on specific tank builds. You should check out a forum like DIYfishkeepers, they will be able to give you further guidance.

The first two products are made by the same company, so if number 2 looks better on paper, it is probably the better product. Here is a quote directly from one of their technical sheets.

“Before purchasing or using any Momentive products, please visit to view our full product and sales disclaimer. GE is a registered trademark of General Electric Company and is used under license by Momentive Performance Materials Inc.
UltraGlaze is a trademark of Momentive Performance Materials Inc.
Copyright 2008-2018 Momentive Performance Materials Inc. All rights reserved.”

It is easy to get carried away with prep work. I am sure it is a bad idea to try and glue two wet surfaces, however moisture is not an issue. If you are looking to reattach a center brace or attach something to the wall, or something similar there is no need to drain your entire tank. Here is a quote from the SCS1200 technical data sheet “The material is supplied as a paste, which cures into a durable rubber when exposed to atmospheric moisture.” It is later stated that the material will not cure in a sealed environment, so give it some time before you submerge it.

Acetic acid is the chemical off-gassing as the material dries. Is that something that should be considered poisonous to the fish? My experience has been that it is really not. MSDS on your product will help you decide for yourself.

My experience with SCS1200 has been very positive on my tank builds of 100 gallons or more. I currently have 2 aquariums built with it. I was also impressed with the knowledge of the technical support staff I spoke to when I was deciding on a product.

It may be worth mentioning that the SCS1200 tech sheet also recommends sealant at least 1/4″ thick to accommodate for thermal expansion. While this is not an issue for an aquarium, it may allow for some flexibility in the joints of an aquarium sitting on a crooked stand. However, another bulletin from the same company recommends no thicker than 1/4″. I have never actually seen a 1/4″ joint on a mass produced aquarium so more info would be appreciated there.

ASI is one of the few companies stating their product is designed for aquarium use. I was planning to try their product based on the recommendations of my supplier. With a little research their product was looking pretty good and was attractive in that it claims to bond most acrylic. Their website states that their product was tested on a 700 gallon tank and held for months. Looking a little deeper, I was not as impressed. Without knowing the dimensions of the 700 gallon tank the information is not very useful. The test tank could have been 6″ tall with several supports and under very little stress.

Today upon speaking to their technical support department, they were unwilling or unable to give any details as to what companies use their product, who built the 700 gallon tank to test their product, how the product should be applied to aquariums, or any other details like, joint thickness specific to their product. I was told to read some blogs and see what other people are doing. The representative did say that a generally thicker joint would be weaker but that they did not have any specific information. An additional concern about the product is that their technical data sheet only offers one ASTM test method in one category, (compared to 7 and 14 from GE) so it is very difficult to compare their product directly to any other. If anyone is considering using their product it may be wise to call them for details first.

Hi Wendel,

You raise some good points. I really appreciate your insight!

Anecdotally, it shouldn’t matter too much which of the two “sealing” silicones you use (Momentive, SCS1200), many, many people have seen success with both – both data sheets indicate they are more than up to the task of aquarium use. While it’s still early days on the Momentive, my SCS1200 tanks have lasted years and I hope for years more. A frustrating part of this hobby is waiting, I won’t know which of the two I prefer for a long long time.

The general consensus in the reeftank community is that acetic acid shouldn’t pose a danger to fish.

Also, thanks for the heads up on ASI, I’ve only ever used it on decorations, which is why I didn’t suggest it as a “sealing silicone” – I am only game enough to recommend those which I have personally used. Based on your experience, I’d be afraid to use it to seal an aquarium.

Can you? Sure, I have read stories were people have used GE 1 for resealing. Should you? Personally, I wouldn’t recommend it or use it myself. It will be much less effort to get a new tube of silicone then it will be to clean up the mess left behind of a leaking tank. Depending on the size of your tank, you may need more than one tube anyway – so if you have to get more, why not get some stronger silicone?

Using the Amazon link you provided, The description for the ge 1 sealant says “Cured sealant is resistant to stain-causing mold and mildew growth”. Has this product changed recently? You mention to avoid such sealants in your article.

Sounds like whoever listed the product has made a mistake, I have a tube on hand I grabbed last week from the local hardware (unrelated issue to fish tanks, Nieces playhouse roof has a leak) I’m looking at the tube now and it contains no fungacides – same as always. I appreciate you being thorough and asking though!

Dear Sir / Madam !
Good Morning.
I am facing some challenges and need your help and advise. In my country, unfortunately, i don’t find Aquarium safe sealant except 2 types. Only what I have seen in local stores are DAP and Loctite Aquarium safe silicons BUT they have clearly written that I can use for maximum for 30 Gallon and aquarium maximum height should be 45cm.

Kindly advise me shall I still go for DAP or Loctite Aquarium safe silicon tubes for my for 95 Gallon (356 Liter) Fish Tank ultra clear crystal glass 12mm thickness which I had purchased from a local glass factory and still have to build/assemble as new very first time.

Dimensions of my Aquarium will be:

L= 121 cm
H = 55 cm
W= 55 cm
Thickness= 12mm

If not then kinldy advise me what shall I use. I have below options only in my local market and this is what I have seen Petshops also using below to make their Aquariums.

– Soudal “Fix All” Crystal
– Soudal “Silirub 2” Universal
– GE Silglaze N10
– Bison “Poly Max” high tack
– DAP “Kitchen, Bath & Plumbing” Clear
– DAP “Window, Door & Siding” Clear
– DAP “Kwik Seal Ultra” Clear

Awaiting for your kind reply,

Best Regards,

Mohammad Asif

Hi Mohammad,

That’s an excellent question. Unfortunately, I cannot give further advice as I have no experience with the Silicone you have listed. Do you have an aquarium manufacturer in your country? Or even an aquarium club? It’s best to start asking here as these people will need to use the same silicone available to you in order to seal a tank. I wish I could be of further help.

hi mohammad….

Located in Chennai …India….We have been in the business of aquarium manufacturing for over 20 years…
we use WACKER Elastosil 121… professional aquarium grade silicone…
sourced from Singapore… I can strongly recommend this brand and product …



I used a tube of GE Silicone 1 Window and Door – CLEAR SILICONE to glue in a glass divider in my new 10 gallon after reading recommendations. Then I read the tube directly under the instructions: “Not for use underwater/aquarium use”. I’m in the middle of cycling the tank. Do I tear the tank apart and redo it? Or does this mean not to apply it underwater?

Hi Richard,

Given the success many aquarists have had with GE Silicone 1, I’d say it means you can’t apply it under water, which is true of all silicones – They are only inert once cured. Given how common it is for aquarists have actually used GE Silicone 1 on their tanks, issues would be widely recorded by now.

Hi Linda,

It would depend on the silicone and how humid the environments is. Humidity can drastically slow down the curing time. If memory serves, Momentive RTV series is something like 3 days for a 50% humidity. If in doubt let it dry for longer.

I have a large bowl shaped ceramic planter – not glazed On the inside that I want to use as a small pond. Do I need to seal the inside? If so it seems like a tube of silicone is not going to be the most effective application. What do you recommend?

Hi Shannon,

My motto is always: When in doubt, seal it or don’t use it at all. Generally for clear coat, you can use a 2-part epoxy resin. Be mindful that it doesn’t spread the same as paint, and can be a little difficult to apply. Terra Cotta Pots are pretty cheap anyway, it might be better to start fresh with a plain brown/orange pot instead. For more info on using pots in your aquarium, check out my Aquarium Terra cotta pot guide


I have a 40 gallon slate bottom I tried to seal with GE Silicon 1 without success. After reading your post I’m convinced I should use either Momentive RTV 100, RTV 103, or SCS 1200. Do you favor one over the others for adherence to the slate?

P.S. Awesome website. I appreciate the work you do!

Hi Raymond,

Wow, it’s been a long time since I’ve heard of anyone having a slate bottom tank. To be completely honest with you here, I have no experience with them. In the old days, they used to seal slate bottom tanks with ashphalt, but that develops leaks over time. If you think silicone sealant adhere to slate, then I would go with any of the above three you listed. They are industrial grade silicones that many commercial tank builders rely on.

Hello I Am doing a reseal on a 90 bow front and was using SCS 1200 or momentum 103 but the momentum is actually quite hard to find in Canada anyway that I’m seeing and my tank is ready to go. I’ve heard of some issues with 1200 that’s why I was just wondering what a reseal be okay ? or should I try to find momentum and just use that?
I can find momentum on Amazon just like I can the SCS 1200 but they want way more like it’s like $12 10oz thing full tube for a caulking gun scs1200 and like I think it was like $68 for 2 tubes of the other stuff the momentum. Only really issue I see is I’ve heard a lot of positive reviews about momentum and I seen a few bad ones about SCS 1200

Hi Dave,

SCS1200 used to be my go-to silicone. My oldest tank at the moment is going on 7 years and was sealed with it. Anecdotally, I have chatted to many other fishkeepers who also use it without issue. Based on this I would suspect that the bigger issue is people sealing their tanks properly rather than the the adhesive qualities of either silicone failing.

We just built a 40 long glass tank braceless using ge 100% silicone sealant for plastic sheets and other plastics. It’s only been curing for 8 hrs. In your opinion do you think this is ok? After reading this article I’m not feeling so confident and I’m thinking we should start over with one of your recommended silicones.

Hi Janie,

Unfortunately, I can’t say for sure how your tank would hold up. If I was in your position, I would compare the Material Data Sheets of the silicone you used vs. That of these silicone. If their qualities are similar, then I would consider still using it. You should be able to get this data from the manufacturers website or contacting the manufacturer directly. From here it’s a judgement call that you will have to make.

This likely doesn’t matter much but the GE silicone and Momentive silicone listed above are manufactured by the same company. Momentive is a strange company, they buys silicone from GE (interestingly, General Electric is one of the only a few producers of raw silicone in the world – it’s a long story that involves government contracts in the WWII era. anyway…) Momentive buys the raw silicone from GE and produces silicone sealants and adhesives. In some cases they license the GE name to sell those products (e.g. GE silicone at Home Depot) in other cases the products are branded “Momentive”. Momentive offers even stronger silicone adhesives if the ones listed aren’t adequate for larger jobs. Momentive produces silicone adhesives used to hold windows on the worlds tallest skyscrapers – they are surely adequate for the pressures we see in fish tanks, even large very tanks. While these adhesives may not be easy to find they exist for industrial applications.

Hi Neal,

Wow, you sound really knowledgeable on the history of silicone. That GE story sounds fascinating! Thanks so much for sharing, I love to learn new trivia like this.

Sorry, but both GE I and Momentive RTV100 Series Silicones should be avoided for aquariums as they both contain 1-5% D4 (octamethylcyclotetrasiloxane), which is NOT good for fish. D4 leaches into water and bioaccumulates, limits fish growth, reproduction, etc. Aquarium-grade silicones have <0.2% D4 by weight. If you look online, you are able to get a 10.2 oz cartridge of ASI Aquarium Silicone for $8.49 on Amazon with free shipping ($8.60 for black), which is only ~$3 more than GE I Silicone, so the price difference is negligible.


I mistakenly used the GE612 formulation to bond layers of foam for landscaping, which contains Octamethylcyclotetrasiloxane. Plan is to cover the foam with a cement coating and wait for it to fully cure and cease pH swinging. Should I scrap and redo or will frequent water changes be sufficient to reduce the impact?

Thank you for the helpful post. I am wondering if the silicone you recommended for sealing tanks is appropriate for larger tanks (180 gallon) or do I need to search for something stronger. I am planning on sealing the bottom and using strips of glass for reinforcement on the inside perimeter.

Thank you in advance.

Hi Chris,

As far as Silicones go, the Momentive or GESCS should be all you need with your glass reinforcing providing additional support. These are the same silicones that many aquarium builders that sell to the public use. One of the guys from the local aquarium club just finished a 120 using momentive – Although that’s still a way out from your size.


I have a small chip and hairline crack in my 70L aquarium. It didn’t seem to be leaking but i emptied it anyway just incase as the chip is quite deep into the corner of the tank. I was thinking of using a sealant just to give it a bit of strength, do you think this would be ok?

Hi Karen,

My advice is to always get a new tank. I don’t recommend using silicone for fixing damaged panes of glass.

Hello, thank you for all the info.
I just build my 370G aquarium, 200x85x80cms, 2mm gap, with Momentive rtv. One of the two you advised.

I read in the comments a claim that both of these brands contain 1-5% of D4, which apparently is not good for fish on the long term. I noticed that it is the only comment you didn’t reply on… worries me. Is it true? Can frequent water changes for the first month take out the major amount? Or, is it simply not true?

I’m now projecting to build a 1000G aquarium. Which of the silicon would fit best? The mesures, 366x105x100cms, I planned the gap to be 2mm. Direct injection system.

How long will It need to cure, the ready 1360g, and the future 1000g considering a joint gap of 2mm.

Thank you

Hi Nero,

I left that one for people to make up their own mind. I have personally used these brands for over 30 years and are the same brand that many custom tank building companies use. I can only comment on my own experience here but, generally, my fish all reach or exceed the expected life span in these tanks. Whether you use them or another is personal choice but in my opinion, if these sealants were dangerous, it would be very quickly identified now given the large “test” sample size in the aquarium community.

As for the construction questions, I do not give personal advice on building a tank for liability reasons.

Hi Ian

What will the steps be to remove old silicone and reseal again, will you use alcohol to clean the surface after scraping of the old silicone leaving the surface clean and dry before applying the new sealant.


Hi Markus,

In my opinion it’s better to see this in action than to describe it in the comments. If you look up “resealing aquarium” on youtube, there are a number of great examples showing you how to do it.

I have a glass tank and had it for now 22yrs, with no problems. size 105cm x 45cm x 45cm, Should I now start to get concerned with the silicone starting to break down and start looking at getting a new tank.

Hi Kevin,

That certainly is a long time, and if I were in your position, I would be monitoring it at least somewhat regularly. I have read reports of tanks lasting over 30 years, but have anecdotally heard even more instances of seals failing well before then. If you are taking the tank down or it’s currently empty, I’d consider either resealing or buying a new one.

If it’s your display tank, then you’ll need to make a judgement call. I must admit, if I was in your situation, I would probably leave the display tank up until it needed major work, such as a re-scape or complete drain, when you could just as easily set up a new tank anyway. That’s my opinion though and certainly doesn’t make it right.

Hello! Do you have any recommendations for use on a plastic drinking water container? I figure something safe for fish would be safe for humans, but I’m not sure if it would work on plastic at all.

Long story short, I have otherwise good water containers (minor cracks) that I’d rather repair than toss and replace.

Hi Peta,

Fish safe doesn’t mean safe for human consumption. If you drank tank water, you would get very sick. Unfortunately, I cannot help you here.

Hi, I’m reading you’re article on silicone caulk. What I’m looking for is what sealant can be used to seal over labels on bottles to preserve them in the aquarium. Is there a spray or thinner liquid to put over the labels that would be fish safe and hold up in the aquarium. Any help would be appreciated.

Hi Carl,

This is somewhat of an unusual request. Have you looked into epoxy resin or a different sealer that dries clear and is inert. I’m not sure if clear plasti-dip spray is another option, since I don’t know what it would do to the ink on the lable.

FYI… it very specifically says on the package that the GE all purpose Silicone 1 that you recommend is… “not for use below the water line or in aquariums.”

Hi Thom,

Thanks for sharing your concerns. This is a broad statement that covers most of their product portfolio. It’s been tested on thousands of tanks without issue, mine included and is likely there to save GE from legal issues in the event that someone uses it incorrectly (adding uncured silicone, for instance) if you allow it to cure, then it’s fine.

I would like a safe, aquarium silicone that I can spray on a fake piece of a resin-type coral. Are there any spray silicones on the market, in a spray can? Thank you.

Hi Jerry,

Have you looked at Clear plasti-dip? It’s essentially a spray that hardens to an inert rubber when it dries. Otherwise there is epoxy resin, but it’s a pain in the butt to apply.

Thank you. Yes, I wrote Plasti-Dip and they confirmed that they have great success with this, with many coats, that is. Thank you.

My question may be different. I have a couple red ear sliders. 175 gallon tank. No leaks and such. My question is with weight. I am thinking of siliconing a egg crate to one side and part of the front and back walls, about 8 inches wide, then adding a couple of pieces of slate on top, so the turtles can have a basking/walking area. Total weight maybe 10-15 pounds. Would any silicon hold this weight? Or do you have a better adhesive. It will be partly submerged, and as water evaporates, it would also dry a bit. Looking for ideas. Currently using a PVC stand, which works well, but I want to free up swim space and lose the pvc look.

Hi Jason,

It sounds like the eggcrate is carrying the weight? The silicone would be fine for wedging the eggcrate in place – silicone is not load bearing here.

Can you elaborate on the Momentive RTV100 Series that you mentioned at the top of the list? I did a search on this and 95% if what i saw ere just a couple of ebay sellers; as if it were a discontinued product or something.

A search also showed that there are a number of different products under the general label of ‘100 series. (RTV102, RTV103, RTV106, RTV108, RTV109, RTV112, RTV116, RTV118). Supposedly each a little bit different from each other. Are there specific ones that are better, or unsafe for aquarium use?

Hi Brian,

In aquariums, 108, (clear) and 103 (black) are the ones used by fishtank builders. As for availability, Are you located in America? I only ask as we are currently doing a new tank build in our local fish club and had no trouble tracking it down a couple of months ago.

I am in America. I didnt have much luck in search results for the 100 series or the 108. There was a couple of 2.8oz bottles of 108, but that seemed to be it. One site claimed to have it but was over $20 shipping on top of tax and a $20 item.

I found the SC1201 fairly easily but no luck with RTV.

Hi Brian,

The 103 looks like it’s on amazon. The 108 seems to be out of stock, but I’m not sure if that’s because of the current craziness we are experiencing. If you cannot find it easily, I’d go with the GSC1200, as long as you are using the correct method to clamp and brace the tank, you’ll do no wrong with it.

Hi there! We’re having to (unfortunately) repair a leak in a 90gal bow front corner tank. Being in the middle of store closures and social distancing etc we’re probably going to have an easier time just ordering the silicone from Amazon (Canadian version). There’s one that specifically mentions aquariums, and one for 1/3 the price that doesn’t and from the info you’ve provided SEEMS to be okay, but I’m wondering if you’re at all familiar with it or can provide any guidance. It’s Red Devil 078060 StormGuard 920 100% RTV Silicone.

Hi Annette,

Unfortunately, I have never heard of this brand. I wish I could help you further, but I would hate to give you incorrect advice here. Have you tried reaching out to Canadian fish tank builders for their experience with it?

Is it possible to do a small seal job by dabbing a bit on the outside of the tank? I do not have an active leak, but am getting some salt stain on a lower corner of a bow front, and no real way to re-home the fish at the moment until all of the quarantines end. I do have the Aqueon product.

Hi Bob,

Do you have an air pump producing bubbles in your tank? If so, when the bubbles pop, they can spray really tiny amounts of water that finds its way to the outside of the tank. As it dries, over time, salt stains can build up. If this is the case, it’s normal and lowering the amount of bubbles often solves the issue.

Hello, I have a small area where algae managed to grow under the silicone. Is it ok if I cut that part out and reseal it instead of removing the entire strip of silicone?

Hi Robert,

I wouldn’t advise this. It may be unsightly, but if you are going to cut a single piece out, then my advice is to reseal the entire tank. I know it’s not the answer you wanted to hear, but it’s the safest method.

Great info. I need advise. I have an all glass aquarium that was made in 1986. I have owned it for the last 18 years. I have never had any problem with it but after I did a complete water change last week it started leaking from somewhere along the bottom. We have emptied it and taking it outside and I bought silicone to reseal it. But not knowing where the leak is should I just peel off all the old silicone and reseal everything? I really don’t know what to do it is 55 gallon by the way

Hi, it looks like the new tube design for the GE 1 silicone tube has the words mold-free on it. Any thoughts on this?

Hi! I’m also curious about this. Just picked up a tube of ge silicone 1, 100% silicone, says 7-year mold free on the label. Doesn’t say additives as far as I can find…

I’ve looked at the data sheets for over a dozen different silicones and ASI is the only one anyone should buy, for 3 reasons:
– it’s cheaper
– it says on the label “tested with aquariums up to 750 gallons”
– it’s one of only two in Shear Strength (water pressure against the glass) >200 psi after full cure

(the exception would be if you want 1 Day cure times rather than 7 Days, and you’re under 30 gallon, and you don’t care about color, in which case GE 1 is your go-to)

The Momentive RTV108 is almost as strong, but it’s twice the price.

The GE SCS1200 is half as strong, and about the same price, but perhaps same-day available at local stores – so if your tank in under 300 gallons or so and you like the SCS1200 color options, you’re good to go there.

The Loctite is the only other Silicone to mention aquarium specifics – which it rates for up to 18″ high walls at up to 30 gallons.

Even the Dow Corning lacks test results.

The one good thing about GE 1 is that it gives you more tool time and less cure time (10 minutes and 1 Day as opposed to 5 minutes and 7 days).

That all said, it probably doesn’t matter what you use under 30 gallons and you probably have a lot of options that will work well under 150 gallons – but there’s no tests to prove it, just guesswork and he-said-she-said experiences.

I know this is a very old thread but how many tubes of the SCS would you recommend for a 150 gallon? Resealing all seams (NOT building). 3/4 in glass so i’m figuring a 3/4 in bead.

Hi, Tony, I’d recommend using about three to four tubes of the silicone sealant. It’s always good to have a little extra on hand in case you need more coverage than anticipated. Also, apply a consistent bead along the seams for the best seal. Good luck with your project!

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