What to Do When a Fish Tank Does Not Heat Up?

A heater is necessary for fish tanks if you live in a cold area or have tropical fish. But if the heater fails to increase the temperature of the fish tank, the fish inside might be in danger.

The majority of tropical water and marine tanks are kept at temperatures between 22 and 30 degrees Celsius. There are a few steps that you can execute to maintain the temperature if the heater suddenly stops

In this article, I will let you know you heat the fish tank without a heater. I will also inform you about the consequences and prevention of a fish tank not heating up.

Why Does the Fish Tank Water Fail to Heat Up?

There are several reasons why the water inside your fish tank is not heating up. Here are the reasons:

  1. The tank is large compared to the heating system.
  2. No presence of a fish tank heater.
  3. The thermostat of the heater is not set up properly.
  4. The heater has cracked.
  5. Fish tank glass walls are not insulated.
  6. No hood on top of the fish tank.
  7. No strong lighting system inside the water.
  8. Sudden water heater malfunction.
  9. Checking on the fish too often by taking off the insulation layer.

These are the typical causes of low temperature faced by most fish tank owners. Salt creeps on the bottom of the fish tank and also causes heating issues.

How to Raise the Fish Tank Water Temperature without a Heater?

If you do not own a water heater for your fish tank, maintaining the temperature can be a hectic job. Also, if the heater has malfunctioned, you need some quick and easy solution until the heater is fixed.

Here are the steps you can take to preserve the temperature without using a heater:

Blankets, Towels, or Heating Mats

You should act quickly in an emergency event such as a heater breakdown or power loss. In case of emergency, keep heating mats.

These are simple ways to raise the temperature of a fish bowl or tank. A nice idea is to wrap the glass panels in a large towel or blanket.

  • Lights and Insulation:The temperature may be kept quite consistently if a powerful light is used within the fish tank. Small fish tanks may be quickly warmed up by leaving them on for 10 to 12 hours each day.

Spend money on insulating layers outside the glass of the tank as well. As a result, it is simpler and quicker to maintain the heat.

  • Using a Hood: To maintain a constant water temperature, install a hood on top of the fish tank. But be sure to include some holes on the hood for a suitable supply of oxygen. You may also use a stone or an air pump.
  • Use a Smaller Tank: Most individuals make the error of purchasing an excessively large fish tank for little fish. Additionally, a huge tank is not necessary if the population of fish is rather low.

A smaller tank uses less energy and takes up less room while still keeping the fishes’ water warm and comfortable

  • Warm Area: Moving the fish tank to a warmer location is an excellent option if you live in a chilly environment. Make sure the fish tank receives at least 6 to 8 hours of direct sunshine daily.

Additionally, put the fish tank higher up because it is warmer.

  • Warm Water Changes: Never add cold water to your fish tank while refilling the water. Always get the water up a touch over room temperature. Also, do not add hot water to the fish tank.

What Are the Reasons for a Fish Tank Not Heating Up?

There are several causes for a fish tank heating issue. If you are using a water heater inside your fish tank and still having trouble, you should check a few things.

First of all, inspect the temperature of the water with a thermometer. Do it before and after heating the water. If you see no change in the temperature, then the heater has malfunctioned.

While changing the water, people tend to forget to unplug the heater. As a result, the heater heats up way too much and becomes damaged. It can also crack under high temperatures due to not being heatproof.

So, if you have the heater plugged in, but still not getting any result, it is time to get a new one. You can get this product from Amazon if you are looking for one online.

How to Use a Fish Tank Heater Efficiently?

You should follow a couple of rules so that the heater can work smoothly as intended. Follow the instructions for efficient heating:

  1. Always maintain an appropriate water circulation. In addition to using a heater, you should also use air stones and pumps. This will ensure that the heat is evenly distributed across the water.
  2. Although the heater is equipped with a thermostat, you can never be too sure. Use an external thermometer to make sure that the temperature is according to the set limit. Check it at least 4 times a day.
  3. You should always unplug the heater while working inside the fish tank. Whether you are relocating the heater or changing the water of the fish tank, never leave the heater on.
  4. Prevent any kind of leak as soon as possible. If you neglect the smallest leaks, you are risking the temperature and ultimately, the health of the fish.
  5. Clean the mineral deposits on the bottom of the fish tank. These minerals and salts gather up gradually which can cause heat deficiency in the tank.

How to Prevent Fish Tank Heater Malfunction?

You should always inspect the heater and figure out if it is working correctly. First of all, fractures might result in fish tank temperature problems. Broken glasses can also be harmful to the fish.

You may use heater protectors to stop these cracks. These prevent the fish from bumping against the heater and shattering the glass. Always keep an eye out for cracks of any type.

Make careful to replace the heater as soon as you can if you detect it has broken. Utilizing a damaged heater might result in an explosion or failure.

Another crucial factor is where the heater is placed within the fish tank. Do not install a submersible heater vertically if you possess one.

If the plug and outlet are not properly maintained, water may enter inside. Making a loop in the wire is one approach to stop this. A “drip loop” is what is used in this situation to keep water out of the electrical socket.


If you have been using a heater for more than 3 years, you may face an issue with the fish tank not heating up. You may always use two heaters if you live in a cold region to relieve the strain on the heaters.

I have talked about all the dos and don’ts of water heating techniques. Follow every one of my recommendations for a heating system that works effectively if you don’t get the results you want.

You should inspect the temperature of the water 3 to 4 times regularly. Your top concern should be to keep the heater from malfunctioning and to have supplies and equipment for power outages.

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Arif H Fahim

Welcome to PetFishTank! My name is Arif. I make an effort to publish educational articles using my many years of expertise as a fish owner.

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