Do Aquarium Heaters Burn Fish?

One of the most significant concerns of anyone who keeps fish, or is looking to begin a new pastime with an aquarium is that of heating the water. While the kinds of fish they are most likely to keep will need warm water, there is a nagging concern that is more of an issue than this.

Do aquarium heaters burn fish? Aquarium heaters can burn fish, although this occurrence is very rare. Depending on the fish, these can become stuck between the glass and the heater, or if the heater is in a horizontal position, they decide it is an excellent place to sleep.

So how likely is it that your fish will be burned by the aquarium heater? Read on to find out how it could happen and what you can do to prevent it. 

Spotting if Fish are Burned

If you are unsure whether or not your fish has been burned, you may not notice by the way they act. Because they live in an environment that is full of predators, a sign of weakness or injury can attract something looking for prey.

A fish in an aquarium is no different and will act as normal. You may only notice a fish that has a burn mark as it swims around. These never look too bad in the beginning, and the signs are the skin appears pale, and their gills appear more transparent than usual. If a fish has been burned badly, this will look worse after a couple of days.

Caring For Burned Fish

If your fish has unfortunately suffered from a burn, you will need to follow some steps.

The first thing to do is to assess the extent of the burn. If it does appear to be worse or getting worse, then depending on the kind of fish, it may not survive.

Tending to a burn is like any other injury, and you do need to prevent further infection. Most of this is down to the mucous layer that protects fish has been compromised. Their immune system will also be much weaker as a result.

One first thing to do is carry out 20% changes of water for a while until you see if the wound is beginning to heal or not. In this time, you do need to keep your nitrite and ammonia levels low. This is more important for the nitrite levels.

There is another thing you can do; however, if you have multiple fish and plants, it may be a better option to do this in a separate tank. You can also dose the water with Stress Coat. This broad-spectrum wound seal helps to add a layer of artificial mucus back over the wound as prevention for infection.

Add one tablespoon of salt to every 5 gallons of water in your tank, or in the separate tank you are using to treat your fish. Be sure to use aquarium salt because this doesn’t contain any additives or anti-caking agents.

How to Prevent Aquarium Heater Burns in Fish

Many aquarium heaters now come with integrated fish guards built-in that keep fish, snails, and other aquatic animals from being able to make direct contact with the heating element. 

The heater guard serves two purposes, it protects the heater from becoming cracked or broken by active fish bumping into it or aquarium decor falling into it, and it prevents fish from being burned by prolonged contact. 

If your chosen aquarium heater doesn’t come with an integrated aquarium heater guard, you can always purchase these separately. A heater guard is the first thing to do, but you do need to be sure it is compatible with your type of heater.

There is one thing aquarium owners need to be wary of, and that is their tank heater must not be touching gravel on the bottom of the tank. Likewise, no part of the heating element should be touching the glass of the tank.

This leads to temperature gradients in the glass. These create tension, and in some circumstances, it can lead to the side of your tank glass cracking.

Heater Malfunctions Instead of Aquarium Burns

We have seen that burns on fish from aquarium heaters are relatively uncommon. It can, however, be more common for tank owners to face heater malfunctions.

Aquarium heater malfunctions usually fall into either:

  • The heater thermostat regulator malfunctions, and the heat becomes way too high for the fish to tolerate, killing them.
  • The heater quits working entirely and no longer heats the tank; the tropical fish in the tank become sick or die from hypothermia. 

Tropical fish can only live comfortably within a few degrees of temperature range, and many require widely different temperature ranges to thrive. This is why monitoring the temperature of an aquarium is so important. 

To prevent an aquarium heater malfunction from killing your fish, the primary preventative measure you can take is to utilize a tank thermometer to check the temperature of your aquarium every day. This way you can see if the temperature is fluctuating. 

While you can’t do anything about a significant heater malfunction that happens while you’re away from home, keeping an eye on it daily while you are at home can help prevent issues before they become deadly. 

Preventing Aquarium Heater Disasters

The most common heater malfunction is that the heating element dies completely, rendering the heater useless. In winter, especially if you keep your aquarium anywhere near a window or other drafty area, this can kill the fish quickly if they are adapted to higher tropical temperatures.

This is a much more common issue with aquarium heaters than burning your fish, and you’re much more likely to have to deal with this problem than fish being burned by it. The safest way to prevent this is to always keep a backup heater on standby in case the equipment goes out. 

This preparation can also be useful if you have discovered your aquarium heater is getting too hot, which means it needs to be replaced ASAP. Rather than leave your tropical fish with no heat and risk making them ill while you buy a replacement, you can immediately swap it out. 

Many of the issues that come with heaters are down to the cost. This is where you get what you pay for, and one that is bought because it is cheap can cause more issues than it solves. Even the suction to the side of the tank can be inferior and what allows your fish to become stuck at the back in the first place.

Purchasing the best heater you can afford is a wise choice and not a waste of money. In the long-run, your fish will be more grateful.

With any heater, you will need to read and follow the installation instructions. You can find some heaters don’t take to certain tank conditions and can suffer from salt creep.

With this creep, you do need to follow a regular cleaning routine. The heater will need regularly cleaning as the salt creep can leave your heater covered in the span of a couple of days. If you let this accumulate, it can be hard to remove, and you could damage your heater by being forceful.

One final thing you must always do is unplug the heater when changing the water. If you have a submersible heater, this needs to be submersed when it is on. Follow the instructions as they say to avoid any damage.


In all reality, there are not many occasions when a properly functioning heater burns your fish. If you choose a substandard one, there is no knowing if the thermostat fails, and it heats higher than it should, or it comes loose and traps your curious fish.

Taking care of your equipment and making sure it is clean and functioning as it should is the best way to be sure your fish don’t receive any heater burns.