How To Raise The Temperature In A Fish Tank Without A Heater?

By Harry RamosLast update: 2024-07-11
How To Raise The Temperature In A Fish Tank Without A Heater?

Depending on the type of fish, you need a certain temperature to maintain the best environment for your aquarium pets.

This is especially important in the winter when the environment temperature can go down to sub-zero or even lower, which is why a lot of people use a heater.

However, what happens if the heater doesn’t work? What can you do to keep your fish warm? In this post, we will show you how to raise the temperature in a fish tank without a heater.

How To Raise The Temperature In A Fish Tank Without A Heater?

There is more than one case in which you have to increase the temperature in your fish tank without using a heater, we will help you address each specific case.

Case 1: When Your Heater Is Broken

What to prepare:

  • A bucket of water

  • A thermometer

  • A blanket, thick towel, or newspaper

  • Other heaters in your house

What to do:

Step 1: Check the situation of the heater

You need to first check to see if the heater light is on. Then, check the temperature in the fish tank using the thermometer.

How To Raise The Temperature In A Fish Tank Without A Heater?

Test the heater for malfunction by placing it in the water bucket and turning it on, then checking the temperature

Step 2: If the heater isn’t actually broken, fix what’s wrong

If the heater works fine in the bucket, try putting it in another place and in another way to see if it functions.

You can try replugging the power cord in the source, don’t let the power outlet touch the water.

If your aquarium heater is battery-powered, try swapping the old battery for a new one.

If the heater is really broken, you shouldn’t fix it on your own, instead, take it to a repairer or the seller. You should get a new one if necessary.

Step 3: Retain the current heat

You can use newspapers to cover the tank as it’s an insulation material.

How To Raise The Temperature In A Fish Tank Without A Heater?

Multiple layers of paper can prevent heat loss. If there’s not enough newspaper available, you can resort to a blanket or heavy towels to cover the tank.

Besides, an aquarium light can help retain the heat too. Turn the light on and don’t cover its hood. But this is only a temporary solution because while the light can keep the tank warmer, it also bothers your fish.

Step 4: Use other heaters

If your aquarium heater is broken but your house still has power, you should try using other heaters available. You can place the heater next to the tank to increase its effectiveness.

Also, you can raise the room temperature to help the fish tank maintain warm, especially during the winter.

Case 2: When There’s A Power Outage

If this happens, causing the heater to turn off, here’s what you need:

  • A thermometer

  • A blanket, heavy towel, or newspaper

  • An emergency heater, tin foil, a jar, and candle

  • Materials to make a floating container

Step 1: Retain the heat

Use a blanket, towel, or lots of newspaper to cover the tank, preventing the heat from escaping.

How To Raise The Temperature In A Fish Tank Without A Heater?

Step 2: Make water containers

A second thing you can do is add warm water to the tank, but not directly. First, boil some water using any alternative fuel or material you have. Pour that water into a thick plastic container that doesn’t melt and you can seal tightly.

Before putting the warm water container in the tank, you should take out some water from it because the water level will rise. Then, place the container in the tank, let it float, you can use multiple containers if the tank is large.

Replace the container or refill it with newly boiled water to maintain heat in the fish tank.

Step 3: Make an emergency heater

First, melt candle wax in a bain-marie way. Then, put some sand into a tall jar, up to a third of its height. Put a wick above the sane and pour the melted wax on top of that. Wait until the wax cools down and turns hard. Put the jar in the tank to increase the heat.

You can cover the aquarium surface with tin foil to protect the fire and keep the tank warmer. Remember to cut out a hole to fit the emergency heater.

Making an extender can effectively support your emergency heater if the tank is high. A PVC coupler can be added below the heater to help it float better.

Case 3: When You Don’t Have A Heater

If you don’t have a dedicated heater for your fish tank, it’s much less convenient and you have to make more efforts to keep the tank warm. Here are a few things you can do:

  • Cover the tank to prevent the heat from escaping the tank

  • Make use of your room heater to achieve a proper temperature in the tank

  • Make an emergency heater or water container

  • If your house temperature is already suitable for the fish, you don’t need to do anything

Is An Aquarium Heater That Important?

How To Raise The Temperature In A Fish Tank Without A Heater?

Some people may say you should buy a room heater instead of an aquarium heater, but it only makes sense if your house temperature is proper. In that case, it will help you save power, money, and avoid any potential problem with an aquarium heater.

Apart from that, however, an aquarium heater is crucial for your fish. If the temperature in the tank declines suddenly, you are in a lot of trouble.

There are several ways for you to keep the tank warm without a heater, but they are all manual and time-consuming.

On the other hand, the heater controls and maintains the proper temperature in the tank automatically. In addition, an aquarium heater is a must in the winter when the temperature can drop to sub-zero.

What’s The Best Temperature In A Fish Tank?

Each type of fish needs a different heat level in the winter, for instance:

  • Betta fish need 76-85 degrees F

  • Tropical fish need 75-80 degrees F

  • Goldfish need 68-74 degrees F

But generally, it’s fine to maintain the fish tank temperature between 75 and 80 degrees F.


We have reached the end of the post and we hope that you now know how to raise the temperature in a fish tank without a heater.

In case something goes wrong, it’s helpful to keep alternatives and heating solutions in your house to protect your fish from the heat loss, like blankets, newspapers, and candles.

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