7 Best Aquarium Heaters with Our Large and Small Tank Picks

A home aquarium is a self-contained ecosystem that needs to remain in balance for the health and longevity of your fish and other tank inhabitants. In addition to keeping your tank water clean and clear, you also need to maintain a stable tank temperature.

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Aquarium fish are generally fairly hardy when it comes to minor fluctuations in tank parameters, but constantly changing water temperatures can induce stress which makes your fish more likely to get sick. The best way to prevent this is to buy an aquarium heater.

So, how do you choose the best aquarium heater for your tank? Keep reading to find out!

Understanding the Different Types of Aquarium Heater

An aquarium heater is a very important part of your fish tank set up if you are going to have tropical fish.  – firsttankguide.net

When it comes to choosing an aquarium heater for your tank, there are several different options. Understanding the basics about each of these options is the best place to start when making your choice because you’ll know which models do and don’t meet your needs.

Here is a quick overview of the top 4 types of aquarium heater:

  1. Immersible Aquarium Heater – An immersible aquarium heater consists of a heating element encased in ceramic or glass that can be hung on the back or side wall of your tank using suction cups. These heaters are usually designed to be installed vertically and should not be full submerged in the tank.
  2. Submersible Aquarium Heater – Easily the most popular type of aquarium heater, a submersible heater can be fully submerged in the water and installed either horizontally or vertically. These heaters look similar to immersible heaters with a heating element encased in some kind of durable housing.
  3. In-Line/Filter Heater – This type of heater is very different from the first two in that it does not hang inside your tank but outside of it, connected directly to your filter line. An in-line heater heats the tank water before it returns to the tank, making it very efficient for heat distribution.
  4. Substrate Heater – Also known as cable heaters, substrate heaters feature a flexible cable with an integrated heating element that can be arranged on the bottom of the tank and covered with substrate. These heaters are great for planted tanks to keep the planting substrate warm, but they are not effective in maintaining a stable temperature for the whole tank.

Each of these heater types comes in a variety of different sizes, each one rated for tanks of a certain capacity. Keep in mind that it is always better to have a larger or more powerful heater than you technically need, even if it costs a little bit more. If you purchase a heater too small for your tank, you’ll have trouble keeping the temperature stable and that could negatively affect your fish.

How to Know if Your Aquarium Heater is Working

Nothing is worse than waking up in the morning to find that your aquarium temperature has dropped by 10 degrees overnight. But how do you keep this from happening? Investing in a high-quality aquarium heater is always a good idea, but you also need to be able to tell when it is and isn’t working.

So, how do you know if your aquarium heater is working?

Most aquarium heaters have a built-in indicator light that shows you the heater is on. For many models, the light glows red when the tank temperature is below the desired level and then flashes green when the optimal tank temperature is reached. Some models have an indicator light that turns on when the heater is activated and turns off when it shuts off.

If your aquarium heater doesn’t have an indicator light, or if you want to double-check that it is working, the simplest thing you can do is buy a thermometer.

A tank thermometer will tell you what temperature the water is in your tank, so you can compare it to the temperature reading on your heater. Keep in mind that the water temperature may be different in different parts of the tank, particularly those furthest from the heater.

In addition to checking the real-time temperature of your tank water, you should also leave the thermometer in the tank for 12 to 24 hours and then recheck the temperature to make sure it still matches the reading on the heater – if it doesn’t, your heater probably isn’t working.

Now that you understand the different types of aquarium heaters and how to use them, let’s take a look at the 7 best aquarium heaters on the market:

The Best Aquarium Heater Overall

Aqueon Pro Aquarium Heater

Fully submersible and backed by a lifetime warranty, the Aqueon Pro Aquarium Heater is not just a superior product, it is also excellent value for the money. Available in sizes ranging from 50 watts to 250 watts, this heater can accommodate tanks up to 90 gallons in capacity. The heater features a shatterproof aluminum core with an electronic thermostat that ensures precise temperature readings as well as easy temperature control.

The Aqueon Pro Aquarium Heater offers a temperature range of 68 to 88 with a +/- 1-degree accuracy. An LED indicator light turns green when the tank is at the proper temperature then flashes red when the unit is in heat mode. An automatic shutoff feature turns the heater off when it is taken out of the water and automatically restarts once it is submerged. Plus, the aluminum core and shatterproof plastic housing ensure even heat distribution whether installed vertically or horizontally.

For durability, performance, and advanced safety features, the Aqueon Pro Aquarium Heater is the best aquarium heater overall.

  • Pros: Shatterproof plastic housing, aluminum core for even heat distribution, sizes ranging from 50w to 250w, 1-degree accuracy, automatic shutoff for safety, green/red indicator light
  • Cons: Larger sizes can be very long (up to 15 inches), housing is black not clear

The Best Small Tank Heater

Tetra HT Submersible Aquarium Heater

If you keep a betta tank or nano aquarium, there is no sense in buying a large aquarium heater. For one thing, a large heater either won’t fit or it will look out of place. Additionally, you’ll be paying for more than you can actually use. For small tanks under 20 gallons, the best aquarium heater is the Tetra HT Submersible Aquarium Heater.

Available in a 50w and 100w size, the Tetra HT Submersible Aquarium Heater is designed for tanks up to 16 gallons in capacity. This heater is fully submersible with a compact design and a single suction cup mounting for easy placement. It features a built-in electronic thermostat that automatically heats the tank water to 78 and it can be installed either vertically or horizontally. It also features an indicator light that flashes red when heating and green for maintenance.

  • Pros: Ideal for tanks under 20 gallons, fully submersible, compact design, automatically heats water to 78, vertical or horizontal installation, red/green indicator light, built-in electronic thermostat
  • Cons: Temperature is not adjustable, not for tanks over 20 gallons

The Best Large Tank Heater

Eheim Jager Aquarium Heater

If you have a very large aquarium, you need a tank heater that is sized to match. The Eheim Jager Aquarium Heater comes in a wide range of sizes from 25w to 300w, able to accommodate tanks as large as 264 gallons in capacity. To ensure even heat distribution, you can also purchase two smaller heaters and space them evenly in your tank.

The Eheim Jager Aquarium Heater features a shatterproof glass construction and TruTemp technology that adjusts from 65°F to 93°F. All models are designed to ensure simple and safe recalibration within 2 degrees and there is an automatic Thermo Safety Control feature that prevents the heater from running dry. With an on/off indicator light, you can always tell if the heater is working and the heater is fully submersible for vertical or horizontal installation.

  • Pros: Shatterproof glass construction, TruTemp technology adjusts from 65°F to 93°F, recalibration within 2 degrees, automatic Thermo Safety Control prevents dry running, fully submersible, vertical or horizontal installation, easy to use
  • Cons: Larger sizes can be very long (up to 15 inches), calibration can be tricky

4 Other Really Good Aquarium Heaters

If none of the aquarium heaters above quite fit the bill, there are still plenty of other options out there! Here are four more really good aquarium heaters you should consider:

Hydor ETH In-Line External Aquarium Heater

If you use a canister filter or external filter in your aquarium, the Hydor ETH In-Line External Aquarium Heater is an excellent option to consider. This heater hooks directly into your filter line and it can be installed outside the aquarium so it doesn’t affect your aesthetics. Setup is easy and integrated temperature control ensures extra precision. This heater is suitable for both marine and freshwater aquariums, and it comes in two sizes with two different hose diameters.

For larger aquariums and external filtration systems, the Hydor ETH In-Line External Aquarium Heater is one of the best options out there.

  • Pros: Ideal for large tanks and external filters, precise temperature control, two sizes/hose diameters
  • Cons: Somewhat expensive, somewhat tricky to adjust temperature, cannot be mounted horizontally

Fluval E Advanced Electronic Aquarium Heater

From one of the most well-known brands in the aquarium industry, the Fluval E Advanced Electronic Aquarium Heater is a durable and reliable option. This aquarium heater comes in three sizes from 100w to 300w and it features a shockproof glass housing covered by a plastic fish guard for an added layer of protection. It features an easy to read LCD display and digital temperature reading with dual temperature sensors and a low flow alert. Plus, it’s backed by a 5-year warranty.

If you’re looking for a high-quality and reliable aquarium for medium-sized tanks, the Fluval E Advanced Electronic Aquarium Heater is a great option.

  • Pros: Shockproof glass housing, LCD display and digital temperature reading, dual temperature sensors
  • Cons: not recommended for horizontal installation, low flow alert can malfunction, fairly expensive

Cobalt Aquatics Neo-Therm Aquarium Heater

The Cobalt Aquatics Neo-Therm Aquarium Heater is unique in appearance from other aquarium heaters but it offers excellent performance and durability. This heater comes in seven sizes ranging from 25w to 300w for tanks up to 75 gallons and it is fully submersible. Adjustable from 66 to 96 in 2-degree increments, this heater features a one-touch temperature control system that is easy to use.

All in all, it is a versatile and dependable aquarium heater for a wide range of tank sizes.

  • Pros: Elegant and shatterproof design, wide range of sizes, fully submersible, one-touch control
  • Cons: Only adjustable in 2°F increments, suction cups don’t always stick

Hydor Theo Submersible Aquarium Heater

The Hydor Theo Submersible Aquarium Heater is made from shock-resistant, shatterproof glass to ensure long-lasting durability. It comes in five sizes ranging from 25w to 200w and it is completely submersible for vertical or horizontal installation. This aquarium heater features a graduated scale for precise temperature maintenance and PTC technology to prevent damage when removed from the tank. Plus, it is great for freshwater or marine applications.

For precise temperature control and excellent safety features, the Hydor Theo Submersible Aquarium Heater is a great option to consider for your tank.

  • Pros: Shatterproof and shock-resistant, fully submersible, vertical or horizontal installation, PTC tech
  • Cons: Temperature readings may not always be accurate, not as durable as more expensive models

Now that you have a better understanding of the different types of aquarium heater available, you are equipped to make the right choice for your tank. Think about your tank size and inhabitants to select the right size of heater then follow the manufacturer’s instructions to install it.

Once your aquarium heater is installed, all you have to do is use it! Set it to the temperature that best suits your tank inhabitants and let the heater do the rest of the work. You’ll still want to check the tank temperature from time to time using a thermometer to ensure that your heater is working, but most of the work is done for you in maintaining the ideal temperature in your tank.

Best of luck with your new aquarium heater!

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