Aquarium Heater (How it works; Why we need it)

Aquarium Heater is mandatory equipment for all tropical aquariums. No tropical fish should be in a fish tank without a heater.

In the following, we will discuss everything about aquarium heaters from what it is; how it works; which one to buy; and tips to use them.

What is an aquarium heater?

An aquarium heater is a small and simple electrical equipment that heats the water in a fish tank.

Why do we need an aquarium heater?

Since most aquarium fish in the market are tropical, an aquarium heater becomes necessary for the majority of the home aquariums. Unless you live in a tropical area, you must get an aquarium heater for your fish. Otherwise, they will die eventually either directly to freeze to death, or from the weakened immune system.

Even if the fish do not die right away, it will become less active when the water temperature is too cold. Very uncomfortable for the fish, and less fun for the fish owner.

How does the aquarium heater work?

An aquarium heater converts electricity to heat. As water absorbs heat quickly, a heater heats the water around it. So to have a heater working, it must be in the water with good circulation. All aquarium heaters will turn itself off once they have reached the temperature of the setting. No need to worry if the water will overheat. If the water gets colder than the set temperature, the heater will automatically turn itself on.

Are Aquarium Heaters waterproof?

Most of the aquarium heaters in the market are fully submersible. It means they are fully waterproof. You can have them completely submerged in the fish tank without a problem. In fact, all of them have a “minimal water line”. If they do not submerge deep enough, the heater will damage itself once it gets too hot. For these full submersible heaters, you might as well position them entirely in the water.

However, there are a few heaters on the market not fully submersible. These heaters have a “max water line” on them. You might not want to keep the water above this line. It can cause an electrical leak. I would not recommend getting these heaters. Not worth the trouble and potential danger.

How to choose an Aquarium Heater?

1. Fully submersible
Yes, I have mentioned this before. Save yourself some trouble and potential harm by getting a full submersible aquarium heater instead of a half submersible heater.

2. Adjustable
Some aquarium heaters are adjustable when it comes to the temperature setting. Some others are non-adjustable. Adjustable heaters are more useful as you can set the temperature at where you want it to be. However, if you are on a budget, the nonadjustable heaters might be a good choice as they are cheaper.

3. Brands
I’d just go for one of the better-known brands. The following are some good examples.
EHEIM Jager heater,
Fluval Electrical Heater
Tetra Heater
Rena Smart Heater used to be on my list as well since I have had good experience with it. Go for it if you can still find them.

4. Wattage
All heaters should have the manufacturer rated wattage and recommended fish tank size on them. Choose the right wattage for your fish tank is essential. By following the manufacturer rated tank size, you can’t go wrong, but neither it is wrong by not following their advice.

The generally accepted rule is to have 2~5 watts for every gallon of water. You may not need that much wattage if you live in a fairly warm place. We will go over this later.

Due to the automated nature of the aquarium heater, we already know the heater won’t overheat the water. So getting a heater rated too high for your fish tank won’t be a problem as it will just turn itself off more quickly. It won’t cost you more electricity at all.

However, you can save money on the heater itself by getting a lower wattage heater. The higher wattage the heater is, the more expensive it is.

The heater’s useful lifespan can also be shorter if it turns itself on and off too frequently. A lower wattage heater has less problem with that since it has to be turned on for a more extended period to sustain the same water temperature.

5. The room temperature matters when it comes to choosing an aquarium heater.
The one thing you might need to pay attention to is if the wattage is way too low. Generally speaking, the manufacturer rated recommended fish tank size is not very accurate. For example, according to most manufacturers, a 50w heater is only good for a 10-gallon fish tank. I have personally used a 50w aquarium heater for a 40-gallon fish tank no problem. The water temperature can be anywhere I want it to be. I have set it at 80F, and it could go to 90F when I needed it to be.

However, there is one crucial factor comes into the play. It is your room temperature. My 40-gallon fish tank always sat in a room where the temperature had never gone below 73F or 22C.

When I moved to a different house, a 50w heater had trouble to keep the water temperature at even 70C in the water. When the room temperature went to below 50F (10C), the water temperature in the fish tank went down to below 70F even as the setting on it had kept it at 80F a month earlier.

So it is important to know the room temperature all year around. If it is a cold room, you might want to get a higher wattage heater to make sure it can heat the water to your target temperature.

Tips for using an aquarium heater

1. Water Circulation
Once again, water circulation is essential in the fish tank. You can position the aquarium heater near the intake of the filter. Or place an air stone directly below it to make bubbles around the heater. Both will increase the water flow around the heater for better distribution of the heat. We do not want hot pockets and cold pockets of water in different parts of the fish tank.

2. Cover up the top of the fish tank
By using a canopy on the top of the fish tank, less heat will be wasted. It also slows the evaporation of the aquarium water.

3. Place the aquarium in a warmer room
As I have talked about my first-hand experience, the air temperature made the 50w heater insufficient for a small 10-gallon fish tank when it is in a cold room. In this scenario, I have to either use a higher wattage heater or move the aquarium to a warmer room. I prefer the latter since it saves me on the electrical bill.

4. Use a separated thermometer
Even the same model heater will have different temperatures at the same setting. You need to use a thermometer for the more accurate temperature reading, and to manually adjust the heater setting accordingly. Yes, even if the heater has a built-in thermostat. Since it is too close to the heat source, it won’t be accurate.

5. Unplug the heater if you plan to move it out of the water
While the aquarium heater keeps the aquarium water warm, the aquarium water also keeps the aquarium heater cool. If you remove the heater from the water without turning it off first, it will burn itself out. Ideally, you might want to turn it off a few minutes before taking it out of the water.

6. Unplug the heater first if you plan to put your hand in the water
As with all electrical equipment, there is always the possibility of electricity leak. Even if the heater is fully submersible. You just never know if it decides to leak and shock you. Better safe than sorry, unplug it before you put your hands in the water.

An aquarium heater keeps your tropical fish alive and happy. Do not skip it as long as your fish are tropical. Do not mix up tropical fish and nontropical fish in the same aquarium. Buy a good heater can last you many years as they do not break down quickly. None of my heaters has broken down since I started to keep tropical fish a decade ago.