The Importance of a Fish Tank Heater

fish tank heater

When setting up an aquarium, there are many aspects to remember.

Between the plants, the gravel, the filter, and the lighting, there are multiple choices for products and machines to choose from.

However, one important item that sometimes gets overlooked is the fish tank heater.

Different fish require different temperatures, so research the needs of the particular varieties of fish you decide to populate your tank with.

Turn Up Your Tank Heat

Fish typically need water temperatures of 80℉ or higher. A water heater is necessary to reach and maintain these temperatures.

Just like tanks come in many different shapes and sizes, aquarium heaters come in a wide range of sizes or capacities with various features to fit different budgets.

One of the most important aspects of aquarium water temperature is maintaining STABILITY.

As a rule of thumb, water temperature should not change more than a couple of degrees daily.

A reliable heater that can maintain a constant water temperature is a must.

Types of Heaters

  • Submersible Heaters
  • Hanging Heaters
  • External or Inline Heaters

Submersible Fish Tank Heaters

Finnex Ray2 Aquarium LED Daylight

Just as their names say, submersible heaters are fitted below the water level in your tank.

Generally speaking, submersible heaters must stay fully submerged, or you risk damaging their heating element.

Therefore, whenever you plan on changing the water or moving the heater or tank, you should disconnect the heater from the power supply and allow the heater to cool before you move the heater or tank.

These heaters are commonly mounted beneath the aquarium’s filter output, where water enters the tank, heating water to the required temperature before it can cool down the tank temperature.

This method keeps a steady stream of heated water circulating within the tank.

Fish Tank Heater Reviews – Submersible Tank Heaters

ViaAqua 200-Watt Quartz Glass Submersible Heater with Built-In Thermostat

One recommended submersible heater would be the Quartz Glass Submersible Heater by ViaAqua.

This particular heater even has a built-in thermostat and a visible temperature setting for a better experience.

The price is very affordable considering the number of positive reviews the heater has received.

The Hitop Adjustable Aquarium Heater is available in five sizes, from 25 watts to 300 watts. The heater has an auto on-off switch to help regulate the water temperature if it drops or gets too hot.

Simply operate by turning the adjustment knob located on top of the thermometer. However, this means you need to stick your hand in the tank water to adjust the knob.

At less than $15, it’s a cost-effective heating solution for your fish tank.

Hanging Fish Tank Heaters

Hanging heaters are designed to hang over the side of the tank, similar to how a filter hangs on the side.

The heating element hangs on the aquarium’s inside, below the water line.

The controls for the heating apparatus are situated on the portion that remains outside the tank for easy access.

Similar to the submersible heaters mentioned earlier, make sure to keep the water level higher than the element of the heater so as not to damage it.

Fish Tank Heaters Reviews – Hanging Tank Heaters

YukiHalu Small Submersible Aquarium Heater

Another great hanging fish tank heater is the YukiHalu Small Submersible Aquarium Heate. This heater is available in five different sizes, from 25 watts to 300 watts. The built-in thermometer accurately controls the tank temperature and stores the last temperature so any power failure doesn’t result in the tank temperature being randomly selected. 

The thermometer has a heating indicator light, and it features a water level sensor, so your thermometer never burns out by being exposed to air by a drop in water levels.

Another great option is the Kulife Fumak 25W Adjustable Aquarium Heater, which is also available in six different sizes, offering a heating solution from 25 watts to 300 watts. The heater is also super short, which means you can easily hide it in your aquarium for a more natural looking tank. 

The heater has a low margin for error, with accurate temperature control up to 1℉, and with automatic temperature maintenance, there’s no need to dial a knob, and it saves on power costs. 

A memory feature is great for when unplanned power outages switch off power as the heater automatically resumes the last programmed temperature. Simply hook the cord and control unit over the side of the tank, suction the heater onto the tank below the water line, and you’re good to go.

External or Inline Fish Tank Heaters

External or inline heaters are attached to the outlet side of the external water pump outside the aquarium.

These types of heaters are often used for medium to large aquariums where the heating chamber can be added to the external filtration system, heating the water before it re-enters the aquarium.

These fish tank heaters are handy if you have live aquatic plants in the tank that might overgrow the heater, causing it harm.

Overly aggressive fish might also try to take a bite out of your heater, so an external heater will keep it protected.

External heaters are also known to be more accurate, keeping your water temperature steady. You can get a quality inline heaters cheaply on Amazon.

Fish Tank Heaters Reviews – External or Inline Tank Heaters

In-line heaters or external heaters can be a little more costly, but they offer several benefits that merit a closer look. 

The DaToo Aquarium External Heater is an elegant external heater for your aquarium. It offers great accuracy in thermoregulation for your fish tank’s water. The unit has two temperature sensors, one at the intake and one at the outlet valve. If you have a canister filter for your tank, this type of heater works really well. A large LCD display clearly shows the water temperature at all times. 

For easy installation, the filter comes with three types of inlet and outlet valves so it can pair smoothly with most types of canister filters. 

The Corisrx in-Line External Heater Aquarium Heater can be used externally to the aquarium. The heating unit should be installed vertically to the tank, with the inlet at the top of the heater, so gravity can assist in returning the heated water to the tank. 

The LCD display shows accurate temperature readings, and the heater continuously heats the water flowing from the tank to the filter and then to the heater before returning to the aquarium. An auto-shutoff helps to ensure the heater doesn’t overheat if the water levels drop.

Installation and Use of Fish Tank Heaters

All heaters have different controls regardless of their position relative to your tank.

Please read the manual that comes with your heater before using it for the first time and definitely before adding fish to your aquarium.

Many internal heaters come with suction cups that will adhere to the side or bottom of your tank but check the packaging for this information before you buy. If they do not come with the proper installation hardware, ensure you purchase fittings separately.

Some heaters come with integrated temperature gauges so you can keep an eye on the temperature in the aquatic environment.

Again, if your heating solution doesn’t include this hardware, purchase a reliable thermometer before you leave the pet supply store. 

Allow plenty of time for your aquarium water to heat up before adding fish, so the glass and water can obtain similar temperatures and prevent the glass from breaking.

You can’t safely add fish to the aquarium when you’ve set it up if you don’t know exactly what temperature the water has been heated to.

Pick the Best and Most Accurate Aquarium Heater

A standard guideline for selecting a fish tank heater is to choose one that can deliver 3 to 5 watts of power output per gallon. The heater’s wattage determines the unit’s ability to heat and maintain the temperature within the aquarium.

For example, a 29-gallon aquarium using a 29-watt heater would equal 1 watt per gallon, which is insufficient to maintain a suitable or stable temperature.

Using two smaller heaters is recommended for energy conservation over one higher-powered one.

If one heater fails, it also increases the chance some of your fish will survive, as the tank won’t lose all heat immediately with the second heater still running.


When installing a fish tank heater, following the manufacturer’s instructions and taking necessary precautions are essential. Proper placement, use of installation hardware, and monitoring of water temperature are key factors for the effective and safe operation of the heater.

Hope this post is useful for you. I would appreciate it if you can share this with anyone who you think might find this article useful too!

Drop a comment below with any questions that you might have or share your personal experience. Thank you.

1 thought on “The Importance of a Fish Tank Heater”

  1. I’ve used hang on heaters in the past and I have to say, I would never recommend someone use them. Especially now that submersible heaters exist, there is no point in having something that could shatter if your water level drops too low.


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