Do Angelfish Need A Heater?

Angelfish are considered tropical fish, and as a result, they require a heater in their tank. Due to the temperatures of rooms tending to fluctuate, it’s necessary to use a heater to keep the tank’s water temperature stable, ideally between 70-85 degrees Fahrenheit. 

Although requiring a heater to maintain angelfish in your tank healthily is necessary, it’s also vital to understand why they require it and the consequences of a tank that is either too hot or too cold. In addition, we can also look at why it’s advantageous to have a tank with a consistently ideal temperature, specifically how it benefits the angelfish.

Why Do Angelfish Require A Heater?

Angelfish are traditionally from the tropical waters of South America, which includes the Amazon water of Brazil, Columbia, and Peru. The water Angelfish originated from and thrive in is generally slow-moving, bright and sunny, somewhat acidic, but most importantly warm.

If you intend to keep Angelfish in an environment meant for display, it’s still necessary to imitate their natural habitat to keep them healthy and happy.

Besides the technicalities of pH levels and adding natural plants for hiding places and laying eggs, the water needs to be similar to the tropical water of the amazon for the angelfish to thrive.

As a result, angelfish require a heater to provide them with ideal temperatures similar to their natural habitat. However, if your environment already has similar temperatures, is it necessary for a heater?

In short, yes. A heater in your tank gives you more control over the precise temperatures without fluctuations or drastic changes.

Being able to control and maintain the temperatures in your angelfish tank will reduce stress and encourage growth.

Striped Angelfish in Planted Tank

What Is The Best Temperature For An Angelfish?

The ideal temperature for angelfish is between 75-85 degrees Fahrenheit. Although temperatures continuously fluctuate, it would be ideal not to go higher than 85 degrees and to avoid dropping below 75 degrees.

Maintaining ideal temperatures consistently will be advantageous, but angelfish are capable of adapting and withstanding minor fluctuations. Angelfish are pretty hardy, and adapting to different temperatures is relatively easy for them, although it does affect their overall health and longevity.

If your temperature drops 5 degrees above or below the general range, it should not do irreversible damage; however, ensure that you don’t regularly fluctuate outside the range.

Angelfish can survive under temperature changes; however, for them to thrive and reproduce healthily, they require ideal temperatures.

What Are The Benefits Of Having An Ideal Temperature?

Keeping fish in the ideal temperatures between 75-85 degrees Fahrenheit foresees healthy living and reproduction. Angelfish who live in ideal temperatures will be more lively, colorful, and healthy.

Ideal temperatures decrease the opportunity for bacteria to grow in the tank and assist angelfish in maintaining a healthy immune system to fight potential diseases.

In addition, Angelfish also tend to reproduce more frequently if they feel safe and comfortable in their environment.

What Are The Consequences Of Having Unsuitable Temperatures?

Fluctuations in temperatures put a lot of stress on angelfish which will shorten their life expectancy.

If angelfish are exposed to temperatures that are not ideal, they will do their utmost to survive, resulting in them being less lively and losing color.

Constant fluctuations and unideal temperatures may result in Ich, Dropsy, and Fin Rot. Therefore, if your angelfish have difficulty swimming, lost their general appetite, developed white spots, or is showing signs of rapid breathing, it’s best to check the temperature and quality of the water to ensure it’s ideal for them.

Angelfish that try to survive in their conditions instead of thriving in them will be much less active, resulting in a dull, joyless fishkeeping experience.

What Are The Best Types Of Heaters For Angelfish?

Depending on your needs and budget, various types of heaters are available to maintain ideal temperatures. Ideally, you want a constant and stable heater to stay within the preferred temperatures.

Various heaters are available, ranging from submersible, half-submersible, in-line, and substrate. Options like in-line and substrate heaters are attractive as they are not visible in the tank but are more expensive.

In addition, effectively installing and running in-line and substrate heaters can prove challenging, and these options are often used by experienced aquarium owners with more advanced setups.

Generally, the most effective heater at an acceptable price tag is a fully submersible one. Although it’s visible in the tank and may disrupt the visual presence, it keeps the water stable and quickly heats it depending on the fluctuations.

Where Should I Place The Heater?

More expensive options like the substrate and in-line heaters evenly heat the water in the tank and entering the tank. Therefore, you can place them in any location that is more convenient for you to maintain.

However, if you use a submersible heater, ensure that it is near the filter where the water flow is at its highest.

Depending on the size of the tank, it will also be beneficial to have heaters on either side of it. Still, as long as there is a heater at the point where the water flows into the tank, the correct temperature will be distributed evenly.

Aquarium Heater with Hang On Back Filter

What Size Heater Should I Have?

The preferred solution is to have at least 3 watts per gallon of water. Higher temperature areas require less wattage, whereas colder areas require more.

A single angelfish will require at least a 20-gallon tank meaning your minimum requirement for heating the water of a single angelfish will be, at the very least, a 60-watt heater.

However, if your area is generally cold and quickly drops in temperature and you have a couple of angelfish, it’s best to have 5 watts per gallon ratio with a 35-gallon tank.

As a result, you will need a 180-watt heater for a couple of angelfish.

It’s important to note that having 90-watt heaters at either side of the tank, especially when you have more than two angelfish, will be ideal as the heat is distributed evenly, which keeps the temperature stable.


Angelfish require a heater to imitate their natural habitat, where they are known for thriving and reproducing. Even if your environment has similar temperatures between 75-85 degrees Fahrenheit, having a heater reduces fluctuations and maintains a stable range, ensuring healthy conditions for your angelfish.