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How to Heat Up A Fish Tank Without a Heater? 



How to Heat Up A Fish Tank Without a Heater? 

Having and maintaining an aquarium is not easy. A lot of things need your attention in an aquarium. From the compatibility of your fishes to their diet, water parameters, and the chemical composition of the tank, it is a handful. But all this is worth it.

An aquarium in a home gives a unique aesthetic appeal to your home and is known to reduce stress as well. Temperature is an important aspect of an aquarium. It is one essential thing that ensures the survival of your fish.

The temperature must be maintained to the liking of your fish. For this, you require a heater. So a heater is an important component in an aquarium. 

But what if sometimes a prolonged power outage occurs. Or worse your heater gets broken somehow. You must think fast and try to keep the water in the optimal range of temperature until you get a new heater or the power comes back.

Well, this article is here for you. We will take you through a multitude of ways by which you can heat your tank without a heater in dire situations.

Heating up a tank without a heater

Sometimes some unwanted situations come up, and you have to resort to certain measures to set things right. As mentioned before, sometimes power outages can occur, and your heater might get broken, and you have to opt for something else to heat your tank. In case of power outages, what you have to aim for is to not let the heat escape from your aquarium. 

Cover your Aquarium 

Covering your aquarium can help you in heating the tank without a heater. With a cover, there will be less proximity between water and the cold air.

So with a cover, the heat gets trapped within the aquarium, and the temperature remains warm. Get an aquarium cover, it’ll help a lot in keeping the tank warm. Although, get one that is easy to open and close for feeding, cleaning, etc. 

But if you’re using a lid, you have to consider the oxygenation of the tank. With a lid, oxygenation can become less, so you will need an air stone and a pump. 

A powerful light 

A power lighting system might have the same warm-up effect as placing your tank in full sunshine. This way, you’ll have greater control over how much light your unheated tank receives.

Leaving the lights on for 8-10 hours a day will easily keep a fish tank warm without a heater. Algae growth may still be a concern in this instance, but there are steps you may do to assist with algae control.

Using a blanket 

This might come as surprising to your but blankets are excellent for insulation. You can use blankets when there is a power outage. The blankets will heavily slow down the cooling down of the tank. What you have to do is wrap a blanket around the aquarium, and this is all you need to do. 

Use an external heater 

If your heater is broken, you can use other heaters in your home. Just turn on the heater and place it near your aquarium. This might not work as well as your aquarium heater but helps keep your tank warm until you bring in a new heater.

Setting up a tank without a heater

All the above-mentioned things are to heat your aquarium in times of emergency. You can set up a tank without a heater as well. Although it is not ideal to keep an aquarium without a heater. But if you want to here is how you set up one. 

Get a small tank 

If you want to keep an aquarium without a heater then a large tank is not for you. A smaller tank of about 10 to 30 gallons is what you should get. A small-sized tank is easy to heat up and once it is heated it is easy to maintain the temperature without a heater. You can use a powerful aquarium light to keep the aquarium heated all the time. 

Get coldwater fish.

If you wish to keep fish in a tank without a heater, you must keep fish that like cooler temperatures. Coldwater fish are often sturdy fish that not only thrive in colder water but are also resistant to frequent temperature variations. Coldwater fish require water temperatures ranging from 60°F to 74°F.

When you set up a tank without a heater, fluctuations are expected. Getting fish that can resist this typical event will only help you later on.

Use external heaters 

Similar to emergencies, you can use heaters to heat your aquarium. You can also increase the temperature of the house using a thermostat. You can keep the heater close to the aquarium to warm up the aquarium. 

Cover the glass panels to insulate 

After you have heated the aquarium to the optimal range of temperature, you can insulate the aquarium. You can use Styrofoam or insulation film for it.

Cover the glass panels on the side and the back. The heat won’t be able to escape the tank or it will slow down the rate at which the tank cools down. 

Perform water changes with warm water

If you have set up an aquarium without a heater then doing water changes with warm water helps in increasing the water temperature.

Using warm water can assist you in getting the tank’s water temperature to the desired level without the need for a heater.

Of course, the temperature will need to be gradually increased. Some fish species may suffer if the temperature rises faster than 1° per hour. You will have to first mix the warm water with some cold water before adding. Do not add boiled water straight to the tank.

What species of fish to keep in an aquarium without a heater? 

If you want a tank setup without a heater then you have to keep fish species that can handle cold temperature and can handle temperature fluctuations. Most species of fish get stressed when they undergo temperature fluctuations. 

Some fish species that you can keep in an aquarium without a heater are Platy fish, Comet Goldfish, Clown Killifish, Hillstream Loaches, Endler’s, Paradise Fish, Rainbow Shiners, and Dojo Loaches. 

All the mentioned fish species can live in temperatures such as 60℉ to 74℉. They are also hardy species that can handle temperature fluctuations pretty well.

Can Tropical Fish Survive Without A Heater? 

Tropical Fishes need a heater for survival. They can survive without a heater but not for too long. Tropical fish species prefer warmer water temperatures, averagely around 74℉ to 82℉. This makes a heater a must for tropical fishes. So if your heater is down or power is out, then the water temperature will go down in a matter of hours. When the temperature goes below the preferred temperature range then your fish will start to become lethargic and might not survive for long in lower temperatures. 

In such a case you will have to preserve the heat of the tank and try to use other methods to heat the tank. Perform all the above-mentioned procedures to heat a tank without a heater immediately. You don’t want your fish to suffer for too long. 

Tropical Fishes that cannot handle temperature fluctuations

Tropical fishes should not be kept in a tank without a heater. As these species require warmer waters and cannot handle temperature fluctuations.

Some tropical fishes that are very sensitive to temperature fluctuations are Guppies, Swordtails, Bettas, Dwarf Gouramis, Neon Tetras, Congo Tetras, Bushy Nose Plecos, and many more. 

If you have these fishes then you have to take immediate action when the heater is not working.


So here it is the methods to heat a tank without a heater. Certain emergencies might occur sometimes and you have to do the procedures right away. It is alright if you want to set up a tank without a heater. There are ways that you can heat the tank and trap the heat in the tank. But a tank without a heater is not recommended, it is not an ideal way to keep fish.

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