Last update: April 22, 2024

Cobalt Neo-Therm Heater Review – Is This The Best Aquarium Heater?

The Cobalt Neo-Therm is one of the most popular submersible heaters on the market.

And if you are here, you have one question on your mind:

Is this heater any good?

Well, you have come to the right place. Today, I am going to take a detailed look at this aquarium heater and whether it’s worth your hard-earned money. (Spoiler, it’s pretty great.)

Already decided you want this heater? Buy it here…

With that out of the way, it’s time to jump into my review.


Small, medium and large Cobalt Neo-Therm aquarium heaters varying in length

Don’t have much room to spare? Use the following table to determine if the Neo-Therm heater will fit inside your aquarium.

SizeTank (up to)LengthWidthHeight
25w6 gal6.55″2.2″0.88″
50w12 gal6.55″2.2″0.88″
75w20 gal6.55″2.2″0.88″
100w29 gal9.72″2.2″0.88″
150w40 gal10.9″2.2″0.88″
200w50 gal10.9″2.2″0.88″

Note: All measurements of the Neo-Therm heater are taken at the longest point when resting in the mounting bracket.

The following specifications remain constant no matter which model of Neo-Therm heater you buy…

Country of manufacturePoland
Power cord length6.5 foot
Temperature range66 – 96°F
Max operating depth31.5″
Outer casingPlastic

What’s in the box?

Cobalt Neo-Therm aquarium heater, suction cups and mounting bracket

Inside your Cobalt Neo-Therm box, you will find…

  • 1 x Cobalt Neo-Therm heater
  • 1 x mounting bracket
  • 2 x suction cups

Oh, and an instruction manual. Read it before setting the heater up in your tank!


Side, top and bottom photo of Cobalt Neo-Therm aquarium heater

The first thing you will notice about the Cobalt Neo-Therm heater is its unusual looks. I think it’s fair to say that this heater doesn’t look like any other on the market.

This heater looks sleek. Yet ugly.

The all-plastic design definitely isn’t going to win any beauty pageants. But hey, it’s shatter-proof. If you drop this heater on the ground, it’s not going to break into a million shards of pain, unlike those glass aquarium heaters.

But where the Neo-Therm’s design really stands out is just how thin it is.

It’s like someone went at an aquarium heater with a rolling pin and the flattened Neo-Therm is the result. Fantastic because it won’t roll off your counter during those occasional cleanings.

Cobalt did an amazing job at creating a heater that is just 1/3″ wide at its thinnest point.

Funny enough, when looking at the Neo-Therm front on, this design makes it look wider than every other aquarium heater.

However, the flat design allowed Cobalt to knock a few inches off, making it one of the shortest heaters around. As you see in the photo below, the shorter length was particularly noticeable in 150W+ heaters.

Cobalt Neo-Therm, Hydo, Aqueon Pro, Eheim TrueTemp 150W aquarium heaters compared side by side
Top to bottom: Eheim TrueTemp, Aqueon Pro, Hydor, Neo-Therm

So, thinner and shorter but thicker when you look at it front on…

But don’t worry, even though it looks like there is more heater to love, the matt black plastic doesn’t draw attention when placed under water. In fact, I was surprised at how well the heater blended in with the black background of my aquarium. If it wasn’t for the light-up temperature display, I wouldn’t notice it at all.

The temperature display sits at the top of the unit and ranges from 66 – 96°F in increments of two.

The Cobalt Neo-Therm heater temperature display is clear and easy-to-read

I cover this display in more detail in the next section.

The final point of interest is the mounting bracket:

Close-up of Cobalt Neo-Therm suction cup mounting bracket

This simple piece of plastic attaches to the glass of your aquarium via two suction cups.

Simply slide your Neo-Therm heater inside, and the bracket holds it in place.

Cobalt Neo-Therm heater sliding inside suction cup mounting bracket

It may be simple, but it’s definitely functional.

Ease of use

The temperature display of your Neo-Therm heater bursts into life the moment you plug it into your powerstrip.

Cobalt Neo-Therm heater temperature display

It might look confusing, but it’s actually very simple to read.

If the water is hotter or colder than the set temperature, two lights display. The flashing light indicates the water temperature while the solid light indicates the heater setting.

The light will flash slowly if the water temperature is less than the temperature setting of the heater. If the water temperature is hotter, the light will rapidly flash to indicate that your water is too warm.

When the heater setting and water setting are the same, only a single light displays.

This unusual method of displaying the temperature may take some getting used to if you are coming from the dial-type aquarium heaters. I know it did for me.

But it didn’t take before I could check the temperature of my tank with just a quick glance. I actually appreciated not having to peer over the top of my aquarium just to see the temperature setting.

When you turn the Neo-Therm heater on for the first time, the temperature will be set at 78°F. If that’s the right temperature for your tank, then that’s all you need to do.

But if you want the temperature higher or lower, you must adjust it. And to do that, use the small button located at the top of the heater.

Button to change the temperature setting of the Cobalt Neo-Therm aquarium heater

Each time you press this button, the setting light moves one space clockwise. So, if I need to change the heater from 78°F to 76°F I must press this button 15 times.

It’s definitely not as easy as twisting a dial. And to top it off, the button is a little stiff.

At first, I didn’t like it. But then I tried to think back to the last time that I actually changed the settings on my aquarium heater. I honestly couldn’t remember!

That’s exactly why this crude system isn’t a drawback at all. Once you set the temperature the first time, it’s unlikely that you will adjust it again. And, the stiff button makes it difficult to change the temperature by accident.

And, the heater has a built-in memory. If you unplug the heater or there is a power outage, you will have the correct temperature when you power it back on.

As for placement, I had no issues mounting the Neo-Therm horizontally or vertically. The suction caps of the mounting bracket held tight for the duration of testing.


I don’t need to tell you… If an aquarium heater isn’t accurate, then it’s as good as useless. You are essentially trusting this thing with the lives of your fish.

So to test the Cobalt Neo-Therm’s accuracy, I brought in the big guns…

Thermal imaging camera, thermometer and probe test equipment for aquarium heater accuracy

I wanted to be confident in my review, so I tested using the following equipment…

  • Flir Thermal Imaging Camera
  • Fluke Digital Thermometer and Thermocouple Probe
  • SP Scienceware Liquid Thermometer

All calibrated with NIST certification.

Cobalt claims that their Neo-Therm thermostat is accurate to ± 0.5°F. That means that if the digital display shows 78°F, then the water temperature could actually be 77.5°F or 78.5°F.

So, how did their claims hold up to real-world testing?

Actually, pretty darn good.

Out of the full range of Neo-Therm heaters tested, no heater was out more than 0.2°F. That’s even better than their claim and makes the Cobalt Neo-Therm one of the most accurate aquarium heater on the market!

If you want an aquarium heater that keeps your water temperature stable, look no further.

Setting Up Your Cobalt Neo-Therm Aquarium Heater: A Step-by-Step Guide

Got a new Cobalt Neo-Therm heater? Great choice! Let’s get it set up so your finned friends can enjoy a cozy, warm home. Here’s how you do it:

  1. Attach the Suction Cups: Your Cobalt heater comes with handy suction cups. Attach these to the mounting bracket. This is where your heater will snugly fit.
  2. Slide the Heater into the Bracket: Now, gently slide your Neo-Therm heater into the bracket. Ensure it fits securely at the top, right near the thermostat.
  3. Submerge Your Heater: It’s time to let your Cobalt heater take a dive into its new aquatic world. Remember, Cobalt aquarium heaters need to be fully submerged to work their magic properly. 
  4. Choosing the Perfect Spot: When placing your heater in the tank, avoid areas with dense algae growth. Also, ensure the heating element isn’t touching gravel or decorations. A clear area along the tank glass or in the sump is ideal.
  5. Secure It in Place: Use those suction cups to firmly attach the heater to your aquarium’s glass. It’s all about stability and safety.
  6. Patience is Key: Wait for about 15 minutes before powering up your heater. This gives it time to acclimate to the water temperature.
  7. Plug It In Safely: Keep an eye on the LED indicator as you plug it in, creating a “drip loop” in the power cord for safety. This avoids any potential water-related electrical issues.
  8. Set the Temperature: Time to dial in that perfect temp. With the Cobalt Neotherm heater, each button tap ups the heat by 2°F. Adjust until you hit your tank’s ideal temperature. Overdid it? No worries, just readjust until you find that sweet spot.
  9. Monitor and Adjust: Keep an eye on those LED indicators. They’ll show you both the set temperature and the current water temperature.

And there you have it! Your Cobalt Neotherm heater is all set to keep your aquarium at the perfect temperature, ensuring your aquatic buddies are living in comfort.

Should you buy it?

I actually loved the Neo-Therm aquarium heater.

It’s not the prettiest thing you’ll ever see. But you know what? It doesn’t need to be.

It just sits there, blending into the background of your aquarium, quietly heating your water.

While it has a few quirks, namely in setting the temperature, this one-off job is hardly a deal-breaker.

Accurate and reliable, it’s everything you want in an aquarium heater.

Just make sure you shop around because these heaters vary dramatically in price. At the time of writing, the cheapest place I saw them was on Amazon.

Highly recommended.

I give it 4.8 / 5 starfish.

What do you think of the Cobalt Neo-Therm aquarium heater? Let me know in the comments below!

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 (8)

I mostly agree with this review. I don’t like that although it is thin, it looks bigger than other heaters because I have mine on the back of my tank and look front on. Really, the thin side should face the front of the tank.

Good heater. I’ve had it for 2 years now and my discus are happy.

Hi Jamie,

Thanks for the feedback. You bring up a good point about the appearance of the heater!

I have had 3 of these fail in less than 1 year. I want to love them but with the high failure rate I will pass.

Hi Rob,

Thanks for your feedback, have you contacted cobalt to confirm that these were authentic? That failure rate seems too high, I have 7 people in my fish club using these in multiple tanks without failure. what heater do you suggest instead?

I did not contact them. I just started using the ehime jager and have been using the same one for about a year and a half with no issues. But as always use what you like and works for you.

Hi Rob,

If it’s not too late, I highly recommend reaching out to them, they have great customer service, you might be able to get a refund? Three neotherms would add up. Good choice! Jager is another I highly recommend, it actually used to be my go-to heater, the only reason I prefer the Neotherms is because they take up less room in my tank and blend better into the background. I’m really happy to hear they are working well for you. I completely agree with sticking to what you like and works!


I had a Cobalt 100 get pretty “algaed” up. What’s the best way to clean this? This is my first go-around with this product and I want to do this right.
BTW-I am a Jager user for many years so I know how to maintenance my glass heaters.



Hi Marie,

What sort of algae are we talkin about? If it’s just the soft mushy stuff, I can remove most of it with a few back and forth swipes with a sponge.

Leave a Reply

Your email address will not be published. Required fields are marked *