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The Best Aquarium Heaters of 2020: Updated Review Guide

It wouldn’t make sense to risk your entire tank on a cheap heater, right?

Well, tons of aquarium owners do it all the time…I can’t tell you how many panicked messages I’ve gotten from people who’s heater malfunctioned and fried their entire tank.

Choosing a high-quality aquarium heater is extremely important. Heaters are often overlooked as “just another piece of equipment”, but this couldn’t be further from the truth. Faulty heaters can kill fish, ruin tanks, and have even been known to start fires.

In this guide, we share our picks for the overall best aquarium heaters on the market along with their strengths and weaknesses.

Best Aquarium Heaters – My Top Picks

Here are my top choices for the best aquarium heater on the market:

1. Cobalt Aquatics NeoTherm

Cobalt Aquatics NeoTherm Aquarium Heater
The Cobalt Aquatics NeoTherm heater ranks #1 on our list due to it's simplicity, accuracy, and durability proven over several years of performance.
Cobalt Aquatics Flat Neo-Therm Heater with Adjustable Thermostat...
  • SUPER-FLAT DESIGN. Fully Submersible, Modern...
  • ACCURATE, ONE-TOUCH SYSTEM. Simply Set Temperature...

My #1 choice for the best aquarium heater on the market is the Cobalt Aquatics NeoTherm. I personally used a NeoTherm for the first time a few years ago and I have never looked back.

The NeoTherm perfectly combines design, performance, and durability into a heater that is reasonably priced, submersible, and completely reliable.

Available Sizes:

  • 25 Watt – up to 6 gallon tank
  • 50 Watt – up to 12 gallon tank
  • 75 Watt – up to 20 gallon tank
  • 100 Watt – up to 29 gallon tank
  • 150 Watt – up to 40 gallon tank
  • 200 Watt – up to 55 gallon tank
  • 300 Watt – up to 75 gallon tank

What Makes the NeoTherm #1?

  • Absolutely no temperature swings: Before I purchased the NeoTherm, I thought it was normal for a heater to cause some small temperature swings once in a while. This is absolutely not the case with the NeoTherm.
  • Low profile design: The sleek black casing is strong, shatterproof, and significantly smaller than other heaters. I keep my NeoTherm in the back chamber of my Nuvo Fusion, but even if I had to put it directly into the tank it wouldn’t look bad at all.
  • Simplicity: This heater is easier to set and read than any other unit on the market. The NeoTherm features a simple dial that is easy to set and a subtle green light to let you know when it achieves the desired temperature.
  • Overall quality: It has an overall solid feel and all of the features, such as the dial, are built extremely well. This heater is definitely made to last.


  • The Cobalt Aquatics Neotherm is only adjustable in 2° increments. If your tank requires an exact temperature, this may be a problem. Otherwise, the NeoTherm is close to perfect!

2. Aqueon Pro

Aqueon Pro Adjustable Heater, 50W
  • Adjustable heat setting 68 to 88°F, Electronic...
  • Shatterproof and nearly indestructible
  • Fully submersible; Auto Shut-Off when over-heats,...

The Aqueon Pro Heater is one of the most popular aquarium heaters on the market. It is moderately priced and can be placed vertically or horizontally in the tank using dual suction cups.

A large, easy to read gauge is placed on the corded end of the heater to allow owners quick access to the adjustable temperature knob.

A notable feature of this aquarium heater is the lifetime warranty. It is pretty rare finding a company that is willing to stand behind their product FOREVER, but Aqueon does exactly that.

If you manage to have any problems with the heater, all you have to do is contact customer service and it will be replaced free of charge.


  • Lifetime warranty and amazing customer service that will address any problems you have, even after years of use
  • Durable material that doesn’t get too hot – your fish/turtles are safe from burns
  • Completely submersible
  • Hold a stable temperature once set correctly


  • There are several complaints regarding the lifespan of this heater, but the lifetime warranty should ease any worries about this
  • Can be hard to get it set to a precise temperature since the dial isn’t very detailed

3. EHEIM Jager

EHEIM Jager Aquarium Thermostat Heater 125W
  • Fully submersible
  • Thermo safey control protects against running dry
  • Will automatically turn off when water level dips...

The EHEIM Jager is a household name when it comes to aquarium heaters. They have been around for a long time and have a solid reputation.

When you buy an EHEIM Jager, you can be assured that it will deliver great performance for 5+ years.

Also, if water levels dip too low or there is any sort of malfunction, the Jager will automatically shut off thanks to the Thermo Safety Control.

Overall, the EHEIM Jager is a reliable heater built to last and well worth considering.


  • Shock-resistant and shatterproof glass body
  • Extremely durable – these heaters can be put through nearly anything without breaking
  • TruTemp Dial allows users to calibrate the heater themselves.


  • Directions for use are poor; some users report the included instructions are unclear.
  • Takes a bit of calibration to get just right

In-Line Aquarium Heaters

In-Line aquarium heaters are different from normal submersible heaters. In-Line heaters sit outside of the main tank and are generally connected between the sump and the main tank.

I generally don’t recommend inline heater, but they do do their occasional uses.

These can be useful for large tanks or for those going for a very minimalist look because they don’t clutter the viewing area within.

That being said, they are a bit more complicated to use than regular submersible heaters because they attach directly to the outflow of a filter.

Hydor In-Line External Aquarium Heater

Hydor ETH 300 In-Line External Aquarium Heater, 300w, 5/8" hose
  • Suitable for marine and tropical aquariums
  • Easy to use
  • High precision electronic temperature control

This Hydor In-Line heater is definitely the “gold standard” when it comes to in-line aquarium heaters. It is easy to install and works well right out of the box. It is also extremely reliable – as long as you buy the right power output you will rarely see temperature fluctuations.

Another reason to use the Hydor heater (and in-line heaters in general) is the evenness of heat dispersal. Unlike submersible heaters that sometimes leave cold spots, in-line heaters evenly warm every ounce of tank water that flows past.


  • Extremely stable – never noticed more than a 1°F fluctuation
  • Evenly heats the entire aquarium – no more cold pockets!
  • Easy to set up and use right out of the box


  • Temperature setting can be off by a couple of degrees

ISTA In-Line Aquarium Heater

150w/300w/500w in-Line External Heater Aquarium Heater - 150/300/500 WATT...
  • The ISTA in-line external heater is designed for...
  • The ISTA External Heater must be used in a...
  • The ISTA External Heater is easily installed by...

Available in 150, 300, and 500 watt versions, the ISTA In-Line heater is the best choice for large aquariums.

Like most in-line heaters, this unit does a great job at keeping temperatures stable while lending to a clutter-free look.

The ISTA In-Line also has an auto-shutoff feature in case water runs dry in the line, eliminating any risk of fire hazard.


  • Available in up to 500 watts – perfect for larger tanks
  • Holds temperatures stable
  • Auto-shutoff feature when no water is present


  • Hose connections don’t always fit perfectly – may require a few zip ties
  • Only shows temperature readings in Celsius – not a huge deal if you don’t mind doing a quick conversion

Do I Really Need a Heater for My Fish Tank?

If you’re trying to start an aquarium on a budget, there are definitely ways to cut costs safely – skipping the heater is not one of them. Here are a few reasons that a heater is one of the most vital pieces of equipment in your aquarium:

  1. Temperature Control – The first, and most obvious, use for an aquarium is for temperature control (duh). That said, it is sometime much more complicated than setting your heater to 78° and calling it a day. For example, my Cory Catfish breeding tank requires specific temperature fluctuations each to to induce breeding.
  2. Stability: Whether you have a cool LED light or searing-hot metal halides, every light puts off some level of heat. When these lights go off at night, water temperatures can fluctuate significantly. A heater helps keep the water temperature at a stable level regardless of room temperature or tank lighting.

Another misconception in the industry is that Betta fish tanks don’t need a heater. They absolutely do!

The climate of the Betta’s natural habitat is relatively warm, so keeping your Betta at 70° in a small bowl is nott sufficient. Ideally, Betta fish should be kept in a 10 gallon tank that hovers around 78° to 80°.

Common Types of Aquarium Heaters

There are several types of aquarium heaters available on the market. In this summary, we will go over the five most common types of heaters that you may come across while shopping.

Immersible Heaters

Immersible heaters are usually hung over the top edge of the aquarium into the water. As a result, a tank with an open hood is usually required. Immersible heaters are generally made of glass, which can pose a few issues.

To begin, glass is extremely fragile and is susceptible to cracks. As with anything else relating to fish tanks, cracks are not good. Therefore, make sure the heater fits perfectly and is not resting against any rocks or decorations.

Since they don’t need to be completely waterproof immersible heaters are also the least expensive type and are carried by nearly all pet stores.

Submersible Heaters

Submersible heaters are made to be completely submerged under water. This allows aquarium owners to move them around and customize where they sit within the set up.

This type of heater is generally more efficient than immersible heaters. They are usually more expensive, but definitely worth it. They provide more flexibility, consistency, and tend to be a lot safer for fish.

Inexpensive equipment usually ends up failing, which costs more money and is potentially dangerous; heaters are no exception!

In-Filter Heaters

As the name implies, in-filter heaters are built directly into the aquarium filter. n-filter heaters tend to be either custom made or are included with all-in-one aquarium kits.

Since your filter eventually cycles all of the water in the tank an in-filter heater can be as efficient as an in-line model if it’s powerful enough!

In-Line/In-Sump Heaters

These heaters are usually located in the sump or connect between the sump and the tank.

External heaters tend to be the safest option in regard to your fish. Since fish can’t brush against them, accidental burns or cracks are impossible.

Though they are very safe, external heaters are sometimes difficult to set up and often expensive. In my opinion, the cost is only justified if you are planning on setting up a huge tank (500+ gallons) which are harder to heat with other designs.

Substrate Heaters

As the name implies, these heaters are buried in the sand or gravel substrate. These are not common in the US, which makes them expensive and hard to find in stores. That being said, they can be great for planted aquariums since they encourage good root health and sprout growth.

Features to Look out for When Choosing an Aquarium Heater

Here are several things you should keep in mind when trying to find the best aquarium heater for your needs:


Because of the inherent dangers related to heaters, it is extremely important to select a shatterproof and shockproof model. Damaging the glass on a heater can cause serious issues, including overheating and electrocution.

I have tested a lot of heaters over my years and the most durable one – by far – is the Cobalt Neo-Therm. The EHEIM Jager is also known to be very sturdy

That durability was continually tested considering I kept it next to rocks in my reef tank. An occasional unstable rock might have shattered a glass heater, but my Neo-Therm remained unaffected.

Tank Size

It is extremely important to get the right size heater for your fish tank. A heater that is too small will not be able to heat the entire tank.

If you tank is too large, the heater will attempt to heat the water 24/7 and never actually achieve the desired temperature, which can cause it to burn out. If anything, it is best to go with an oversized heater.

A good rule of thumb when it comes to heater size is 3-5 watts per gallon. For example, a 20 gallon tank will generally need a 60 to 100 watt heater.

In addition to this basic rule, you can simply check the manufacturers recommend size. They will usually suggest a minimum wattage for each tank size.

Important Safety Features

Because heaters can single handedly “make or break” a tank, safety features are a great asset. Automatic shut off functions and temperature sensors are highly desired by most aquarium owners.

In the case of unexpected water level drops, and automatic shut off will turn the heater off to prevent fires. Temperature sensors that shut down or start the heating element can also provide peace of mind.

Final Thoughts

As you can probably see, picking out an aquarium heater really depends on your budget and needs. For those on a small budget, the Aqueon Pro and EHEIM Jager are both great choices.

The lifetime warranty of the Aqueon Pro is a huge bonus and very reassuring, especially when considering how finicky heaters can be. With a lifetime warranty, you will never have to worry about a faulty heater again.

The EHEIM Jager offers a bit more performance compared to the Aqueon Pro. We noticed less complaints, and the three year warranty is nothing to scoff about.

If money is not a concern, the Cobalt Neo-Therm is an exceptional heater. The flat, compact design gives it a modern look and allows it to fit in even the tightest spaces.

Overall, any of the units on the list can provide ample, consistent heating if used and taken care of properly. Remember to keep your heater well away from rocks, filters, and decorations – happy fish keeping!

Jason Roberts
About Jason Roberts
Jason is an aquarium fanatic that has been a fish hobbyist for almost three decades.

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