How To Choose An Aquarium Heater? [Aquarium Heater Guide]

In this article, I’ll talk about how to choose an aquarium heater and provide you with the ultimate aquarium heater guide. Most of the aquarium fish that you get at your PetSmart or Petco, like guppies and bettas are not gonna do well at normal room temperatures that you’re comfortable with. For example, imagine you as a human being kept in 50°F weather all the time with no extra clothes, and let’s see how long you last now.

Because of my recent Aquarium heater failure I had to buy a new one. So I figured let’s talk about what do I look for while buying a new heater for an aquarium.

In this article I’ll talk about how do I choose an aquarium heater, what do I do if they break, and then what are some of the things to keep in mind while buying an aquarium heater.

How To Choose An Aquarium Heater? [Aquarium Heater Guide]

1. Heater Size

The typical thumb rule is 5 watts per gallon which means a 20-gallon aquarium would need a 100-watt heater. However, that is if you want to raise the temperature by about 10 degrees Fahrenheit.

If you want to do it even more because you know let’s say your aquarium is in a really chilly office setting or if you live in Colorado where we keep our house pretty cold the formula is actually 10 watts per gallon so for this 20-gallon aquarium.

I’m actually going to get a 200-watt heater. Now you may think okay easy enough just get a 200-watt heater actually. The answer is no. It is also important to consider how many aquarium heaters to buy.

2. Number of heaters

It’s better to have two heaters instead of one. If you’ve ever tried to buy a heater before and look at the Amazon.com reviews. There are a lot of negative reviews regarding failures. Heaters just fail and most of the time when they fail they just completely go cold.

So that means your fish are going to freeze to death. Sometimes the heaters get too hot and your fish are going to cook.  Now if I had two 100-watt heaters instead of one 200-watt heater then I’m going to put them both on each end of the aquarium.

Most likely both of them aren’t going to fail at the same time. So if one goes cold at least the other heater will still be able to keep the temperature relatively warm and then if one gets hot well at least it won’t get as hot as a 200-watt heater would have.

It will not do as much damage basically so having two heaters instead of one is kind of like spreading out your risk.

3. Heater Features

For the most part, heaters are pretty simple. Nowadays some of them have gotten really complicated like they have wi-fi connectivity, they have low flow sensors and all sorts of stuff.

You should mainly look for two things in an aquarium heater. I want it to be adjustable because if I want to keep a fish that needs cooler temperatures versus hotter temperatures then I can just use the same heater.

The second thing I want is a heater guard or basket. So that my fish won’t ever get stuck next to the heater. the heater guard is kind of a nice thing to have to keep your fish away from the heater.

4. Installation Tips

The first thing you do is when you put your heater into the aquarium do not plug it in. Most of the instructions usually ask you to wait about 20 to 30 minutes before plugging it in, So it can soak in the water, acclimate to the temperature, and then not have any breakage potentially from temperature shock.  

Ideally, you should install your heater next to a filter or a powerhead and have good water circulation on it. Because if it’s in a really stagnant area that’s clogged up by plants then there’s a lot of hot water and hot spots can form around the heater. You want that water current blowing the warm water to the rest of the aquarium.

All the aquarium heaters I use are submersible meaning they should be completely underwater you do not want to run it dry otherwise it might crack or burn out and that can be a problem during water changes.

Finally, I like using a lid on all of my aquariums just because it tends to keep that heat in there’s less evaporative cooling and then that helps me save electricity in the long run.

5. Temperature Controller

I don’t know about you but I don’t really look at the temperature of my aquarium very often. I just assume it’s working. The reason why I like these controllers is that it has an alarm for if the temperature gets too high or too low. So yes, temperature controllers can seem really extra but in this case, it probably saved a lot of my fish’s lives.

Another reason why I like temperature controllers is that there is this theory that the reason why heaters fail so often is that they’re constantly having to cycle on and off. Imagine turning a light switch on and off repeatedly you know eventually that switch is probably going to break faster than if you just left it on or off for long periods of time.

The same thing with our heaters is that every time they go down by a degree, half a degree, or whatever it is, they automatically have to switch on, and then they switch off again and then switch on again.

So instead the temperature controller allows me to set it so that this switches on until it reaches 78°F and then it turns off until the water naturally cools down to 74 degrees which takes a while for even a 20-gallon aquarium. Then it turns on again and that means less power cycling for this heater and hopefully, it’ll last longer in the long run.

Digital thermometer

If you’re looking for a cheaper alternative, I also use a lot of just digital thermometers that have an alarm on them so it goes beeps when it’s too high or the temperature is too low. Just be aware they do have batteries that eventually run out so keep an eye on that.

In this article, I’ve talked about how to choose an aquarium heater and what things to keep in mind to keep fish safe from the heater. You can also check out other insightful blogs on animal care on our website.