Do Fish Really Need a Heater or Multiple Heaters?

koi fish

If you are new to owning an aquarium, you probably have a lot of questions that you need answers to in creating the best environment for your wildlife. One of those questions will be whether or not your fish needs a heater.

In this article, we will be offering tangible insights into how important or not a heater is for fish and how you can take advantage of that information.

So, follow through as we explore.

Do Fish Really Need a Heater?

The temperature of your fish is based on different factors. The most obvious factor will be the water source for your fish tank. If you are planning to have a tropical fish tank, the water from your water source might not be warm enough for your fish. It, therefore, means that your fish will need a heater.

The surrounding environment is also an important factor. The heating systems you already have in place and the kind of fish species will play a major role in determining whether the fish need a heater. If you have warm weather all year round, your fish may not need a water heater.

Generally, locations that are close to the equator have warm weather so, if your location is around there, you should have consistently warm weather. However, weather sometimes might be unpredictable so, having a heater on hand will be quite beneficial for your fish.

The heating system in your house also determines whether your fish will need a water heater or not. If you have a heater in your house and it matches the water parameters that you need, then you might not need another heater. Having insulation will come in handy to keep your house and fish tank warm.

You should also take into account the kind of fish that you want to keep. Goldfish, white cloud minnows, and some loaches prefer cooler water parameters. You might not opt to use a heater if you want to build a cold-water tank.

You have to put into consideration the lighting for your fish tank. The lights will heat your tank and if the tank is exposed to direct sunlight the temperature of the tank will rise. In such scenarios, you might not need to have a heater.

Another thing to consider will be the draft in your room. It is worth noting that the draft in the room can alter the warmth of the tank. So, a cool breeze compared to water temperature is the way to go. You might have to get a heater for your fish in this case.

Water movement is also something to put into account. Tanks with a current that moves all around will be more consistent with their temperature than tanks that have dead spots or are stagnant. The more water you have in your tank will also affect the temperature of the tank.

Do Fish Need Multiple Heaters?

Some fish keepers like to work with multiple heaters for their fish. A major reason for this will be down to emergencies. If one heater starts malfunctioning, the other heater can fill in without having issues with the temperature of your tank.

If you are working with a long tank for your fish that does not permit a lot of flow running through the water column, then, a second heater will be crucial. You might need to place a second heater at the other end to help ensure that the temperature is constant throughout.

Based on many observations, heaters do not have a long lifespan. So, if your fish need heaters, you should have a spare so that you can be better prepared for any such emergencies.

It is also a very good idea to have standalone thermometers in your fish tank. This is because sometimes your heater might not correctly read how warm or cold your fish tank is. So, if your heater is no longer functioning as it ought, checking your standalone thermometer will give you an idea of its effectiveness.

A standalone thermometer will help you measure your temperature in different areas of your fish tank. This will help you know if your area is cooler than another. So, you can then decide whether to increase the water current or add another heater.

How Many Kinds of Heaters Can a Fish Use?

Among a list of many available heaters, there are two common ones that your fish can use. They include submersible heaters and in-line heaters.

So, let’s go on and discuss them in detail.

– Submersible Heaters

As the name implies, this kind of heater will be required to be submerged in water. It comes with a coiled element that is usually placed inside a glass or plastic casing to heat your fish tank. For best practices, you should place this heater quite close to the intake of your filter.

When the heater is close to the filter, the heated water will be able to spread well to other parts of the tank. If the heater is elongated, then, you can place it horizontally. You could also place it close to a 45-degree angle so that it can heat more water.

Placing a long heater in a vertical position is not very effective. This is because heat rises in the water, so to maintain a warm temperature all across, this position might not be all that effective.

If you want to go for a submersible heater, you should go for one that uses a plastic case or shatter-proof case. These heaters are less prone to cracking or breaking as opposed to when you use heaters that come with glass.

– In-Line Heaters

These heaters are designed to heat water as they pass through tubing. The heater is usually placed between the output tubing of a filter and the outtake where the water from the filter is returned to the tank.

When working with this kind of heater, you may potentially run into water leakages if your tubing is not firmly fitted. This kind of heater is also quite expensive as compared to the submersible heater. So, the submersible heater is the better of the options.

Are There Any Problems With Using a Heater For Fish?

As much as heaters are amazing devices that do a lot of work with heating the temperature of your fish, they can also be a part of the problem. It will go into temperature shock when it gets too hot in your tank. This means that both sides of the spectrum might not be ideal for some kind of fish.

If your fish stays in an environment that is too hot might lead to death or accelerated ageing. This means that both sides of the spectrum could be dangerous for the fish to swim around. So, when the heater overheats, it can lead to disastrous situations.


Several factors come into play to determine whether your fish need heaters or not. The temperature of the environment, current movements, the fish species, and the lighting amongst others determine whether your fish will need a heater or not.

We have reviewed some of the factors in detail in the course of this article. We’ve also considered whether multiple heaters would be a good consideration and the kind of heaters you can work with for your fish.

Written by Justin Michaels

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