How to Choose the Right Aquarium Heater?

There are a few things to consider when choosing an aquarium heater, such as the size of your tank, the climate you live in, and your budget!

Let’s dig into detail…

Size is probably the most crucial factor when choosing an aquarium heater. You’ll need to know the gallons of your tank so you can purchase a heater that is rated for that size. It is vital to get a heater that is the correct size for your tank because if it’s too small, it won’t be able to heat the water properly, and if it’s too big, it could overheat the water.

The climate you live in will also affect what type of aquarium heater you need. If you live in warmer weather, you won’t need as powerful of a heater as someone who lives in a colder climate.

Your budget is also something to consider when choosing an aquarium heater. Heaters can range in price from around $20 to over $200. It’s crucial to find a heater that fits your budget but also does an excellent job of heating your tank.

Some other things to keep in mind when choosing an aquarium heater are the warranty, the features, and the energy efficiency. Finding a heater with a good warranty is important if it breaks down within the first few years.

The features of the heater are also something to consider. Some heaters come with automatic shut-offs, thermostats, and timers. These features can be beneficial in keeping your tank at the correct temperature.

Finally, you’ll want to consider the energy efficiency of the aquarium heater. Heaters that are more energy efficient will cost more upfront but will save you money in the long run on your electric bill.

Now that you know some things to consider when choosing an aquarium heater, you can start shopping for the perfect one for your tank. There are various types and sizes of heaters available, so you should be able to find one that fits your needs perfectly.

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Does My Aquarium Need a Heater?

If you’re keeping tropical fish as pets, they’ll likely need a heater to maintain water temperatures around 78-80°F. Most fish are cold-blooded animals that rely on their surrounding environment to regulate body temperature, so if your home is usually cooler, your fish will need a heater to remain comfortable.

Most aquarium fish can tolerate cooler temperatures than recommended because, in nature, the environment dips several degrees at night or during rainstorms. However, keeping the water at a steady warm temperature is less stressful on your fish and helps prevent diseases. Some species – like goldfish, Japanese icefish, and white cloud mountain minnows – enjoy cooler temperatures and would be fine without a heater. Other fish – like discus, ram cichlids, and certain Apistogramma cichlids – prefer hotter temperatures around 85°F and require a heater. By understanding the temperature preferences of the fish you’re trying to catch, you can better match the conditions of their natural habitat and improve your chances of success.

What Size Aquarium Heater Do I Need?

If you’re a fisherman, the general rule of thumb is 5 watts (W) of heat per 1 gallon of water if a) you need to heat the water to 10 degrees above room temperature, if you’re using an aquarium lid to retain warmth and prevent evaporative cooling. For example, if you have a 29-gallon tank under those conditions, the suggested heater size is 100 watts. However, if your home is on the colder side at 65°F and you need to raise the water temperature by 15 degrees, consider adding a second heater. This will ensure that your fish stay healthy and comfortable in their environment.

Recommended heater sizes for different types of aquariums:

Aquarium SizeHeater Size
5 gallons25W to 50W heater
10 gallons50W to 100W heater
20 gallons100W heater
29 gallonsOne or two 100W heaters
40 gallonsTwo 100W heaters
55 gallonsTwo or three 100W heaters
75 gallonsThree 100W heaters

Other factors that impact a fish tank’s temperature include its location in your home, how much sunlight the room gets, and whether or not it’s near an air conditioner. Additionally, because heat naturally rises, the tanks at the bottom of an aquarium rack will be cooler than the tanks at the top. Furthermore, equipment such as lighting and filtration contributes to the total heat produced in an aquarium. For example, a Fluval FX4 canister filter runs on 30 watts of power and therefore acts like a mini heater in your aquarium, slightly heating the water as it flows through the filter.

If you have a large tank that requires 200 watts of heat, we recommend purchasing two 100-watt heaters instead of one 200-watt heater. This way, if one heater malfunctions, it will not overheat the entire aquarium. Having two heaters also provides a backup in case one shuts off. This will prevent the water from getting too cold.

Where Should I Put My Aquarium Heater?

There are a few things to consider when deciding where to place your aquarium heater.

  • First, you need to ensure the heater is not in a place where it can be knocked over or damaged.
  • Second, you need to ensure the heater is not too close to any other objects in the aquarium so that heat can circulate properly.
  • Finally, you need to ensure the heater is not in a place where it will be in the way or difficult to reach.

With these things in mind, the best place to put your aquarium heater is usually on the back or side of the aquarium near the filter.

What to Consider When Choosing an Aquarium Heater

There are many aquarium heaters, but most of them function similarly. An aquarium heater typically has two main parts: a heating element and a thermostat. The heating element is usually made of metal and is responsible for generating heat. The thermostat is a temperature-sensitive switch that turns the heater on and off to maintain a consistent water temperature.


Most aquarium heaters have a built-in thermostat, but you can also buy separate thermostats that can be used with any type of heater. Aquarium heaters come in various sizes and shapes, so it is essential to choose one that is appropriate for the size of your aquarium. Smaller aquariums may only need a small heater, while larger aquariums may require a larger one.


When choosing an aquarium heater, it is essential to consider the unit’s wattage. The wattage indicates how much power the heater uses and how much heat it can generate. Higher wattage means that the heater will use more electricity and generate more heat.


When choosing an aquarium heater, it is also essential to consider the aquarium size. If the aquarium is too tiny, the heater may not be able to generate enough heat to keep the water at a consistent temperature. Conversely, if the aquarium is too large, the heater may use too much electricity and overheat the water.


Finally, it is essential to consider the type of aquarium you have when choosing an aquarium heater. Freshwater aquariums require different kinds of heaters than saltwater aquariums. Be sure to select a heater designed for the type of aquarium you have.

Now that you know more about aquarium heaters, you can start shopping for the perfect one for your needs.

There are many aquarium heaters, but the most common type is the submersible heater that operates completely underwater. The water current helps spread the heater’s warmth to the rest of the tank. Ideally, the heater should be placed next to the filter output or pump for maximum flow. Install a thermometer in a corner opposite the heater to make sure the heat is reaching the other side of the tank. This will help ensure your fish are healthy and comfortable in their new home.

Some heaters must be positioned vertically, while others can lay down horizontally. For long, tube-shaped heaters, we recommend mounting the heater at a 45 degree angle to get the best heat distribution. You can conceal the heater by placing plants and decor in front of it or hiding it in the sump if you have one.

Do You Leave the Aquarium Heater on All the Time?

As a general rule of thumb, you should always leave your aquarium heater on. This will help to maintain a consistent water temperature, which is critical for the health and well-being of your fish. There may be times when you need to turn the heater off for short periods, such as when you are cleaning the tank or doing routine maintenance. However, as a general rule, it is best to always keep the heater on.

Yes, you could depart the heater 24/7. Aquarium warmers have an inner thermostat that turns off the warmth while it reaches a particular temperature; for this reason, preserving the water temperature inside some levels of the preferred setting.

When first putting in the heater, permit the device to acclimate to the aquarium water’s temperature for 20 to half-hour earlier than plugging it in, to save you breakage from temperature shock. Also, the heater should constantly be submerged in the water while it’s grown. (Sometimes, you’ll see a line at the heater that marks the minimal water level.) Otherwise, it can not appropriately study the water temperature and efficiently manipulate the heating. If you depart the heater jogging simultaneously as uncovered to dry air, it can burn out or crack, so don’t forget to unplug it or flip off the electricity strip while doing water changes.

Thankfully, warmers now no longer require a good deal of upkeep until you need to apply a toothbrush to softly scrub off algae. However, when you have to put off the heater for a few reasons, producers propose ready at least half-hour for it to settle down earlier than handling.

What Is the Best Aquarium Heater?

Out of all the supplies you need to buy when setting up a new fish tank, the aquarium heater is not one to skimp on. You want to find a good quality brand that is safe and reliable because unproven brands may fail by overheating, shutting down, or cracking – all with disastrous results. We personally would not recommend getting a used heater because you have no idea if the previous owner dropped it, left it running while out of water, and so forth.

We designed our own Aquarium Co-Op 100W heater with the goals of having excellent quality and a full range of features, such as:

  • The small, compact design makes the heater easier to position in the aquarium and hide behind decorations or rocks.
  • The digital display provides a large temperature reading that can be clearly read.
  • The heater guard is a protective plastic cage around the heater that prevents fish from wedging themselves and getting stuck behind the heater. (Yes, I’ve actually had fish die this way.) This enclosure also shields the heater from larger fish species that may crash into it. 
  • The adjustable temperature feature is useful in case you need to raise the temperature to treat diseases or lower the temperature to induce breeding. Unlike most heaters that use temperature dials, the Aquarium Co-Op heater has a simple button controller that is located outside of the fish tank so you don’t have to get your hands wet to change the temperature.
  • The extra-long, 11.8-foot power cable makes it possible to reach faraway wall outlets, even if you have a deep aquarium.
  • The suction cups allow you to firmly mount the heater onto the aquarium wall, and four extra suction cups are included as replacements.
  • The 1-year warranty and automatic over-temperature protection offers you peace of mind from heater malfunctions and manufacturing errors.

If you have a nano aquarium that holds 6 gallons or less, consider using the Fluval 25W submersible heater that is preset to maintain a temperature of 76-78°F.

Bottom line: don’t try to save money on heat. Give your aquarium fish a warm and comfortable home, and they’ll thank you for it with hours and hours of entertainment. 

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