How To Keep A Fish Tank Warm Without A Heater

How To Keep A Fish Tank Warm Without A Heater (Detailed Guide)

Every living being is habituated to a particular environment. The chances of survival slim down when they are taken out of their suited surroundings. A similar situation takes place with fish. Even though the aquariums are designed in a way that the fishes would successfully adapt to it, there can be certain negative instances.

Aquariums are required to have a 22-30 °C (71-86 °F) temperature to provide a convenient living experience. Generally, this is fulfilled by a fish tank heater. But there could be times where the heater would stop working due to a malfunction or shortage of power.

In case such a situation strikes, do not panic. We have got you covered with some of the most innovative and simple ways that can keep your fish tank warm without a heater.


Importance of Heater in a Fish Tank

Heater in a Fish Tank

If you are planning on getting a fish, especially a tropical one, you must understand the importance of keeping a heater.

With the help of a heater, you can easily prohibit the fish tank from getting too cold. Irrespective of the room temperature, the tank sustains its ideal heat. This holds utmost importance, especially for tropical fishes.

So, do you require an aquarium heater? Well, yes but it also depends on your region as well as the types of fish.

If you are living in a warm region and you prefer having freshwater fish, you might not require a heater in the fish tank. However, if you live in a cold region and have your eyes on tropical fishes, you MUST have a heater in the fish tank.

Some people prefer getting a room heater instead of a fish tank or aquarium heater. As tempting as this idea sounds in economic terms, it might not work for a betta or tropical fish.

Hence, it is well-established that heaters are a necessary addition when it comes to fish tanks. But what if they fail to work one fine morning? Let us understand some of the possible solutions for the same.


Ways to Keep the Fish Tank Warm without a Heater

There are several ways that you can use to maintain the correct temperature of your fish tank. Go through the entire list and utilize the one that fits well with your circumstances.


Retain the Heat

The first thing that should be done almost instinctively is to retain the heat. You can do so after checking the heater. Either there could be a power outage or an obstructed heater.

Regardless of the reason, try to cover the tank with such a material that could prevent the remaining heat from escaping the tank.

This can be done by a lid. You can simply cover the tank with a sturdy lid or hood to avoid the dispersion of the heat.

In its absence, you can utilize other materials like blankets, newspapers, thick towels, etc.

With the tank covered, it is more likely for the heat to be retained in the tank itself, even in the absence of a heater.

However, if you are worried about the oxygen levels, you can place an air stone in the tank to make up for the reduced oxygenation.


Bring in Extra Heat

Till you find an alternative for a power source or your heater, you can resort to some artificial heating appliances. You can do so by placing aquarium lights.

It is seen that such lights can provide a substantial amount of heat for tropical fishes. This can help in providing a temporary environment according to their requirements.

But make sure you check the temperature changes. These lights can cause a dip in the temperature as soon as they are removed from the proximity. So, it is vital to find a difference when it comes to the right temperature.

If you have a heater in your house, you can use it to generate heat in the water tank. No, we are not asking you to put the heater in the tank. But you can place it near the tank.

This solution can only work if you have power in your house. But if you do, you can stabilize the temperature in the fish tank without any hassle.


Use Boiling Water

Use Boiling Water

Even though this solution is short-term, it is a rather effective one. You can boil some water for the fish tank but do not pour it directly.

Start with removing some quantity of water from the tank.

Boil some water and pour it into water-tight containers. Make sure that they are sturdy and do not end up melting because of the boiling water.

You can try adding a  drop of dechlorinating fluid inside the container to prevent the water from leaking outside. After having done this, place the container in the center of the aquarium.

Avoid placing it at the edges of the tank to avoid any accidental squishing of your fish. Moreover, placing it in the center can gravitate the heat to all corners of the fish tank.

Verify that the base of the container is reliable and won’t tilt down. Keep checking the temperature after putting the container. If you see a dip, refill the container with more boiling water.

As this technique requires constant monitoring and attention, more people do not prefer it, However, this is a good alternative when there is no power.

Note: You must never add the boiling water directly to the tank. This will directly affect the temperature and the fishes in an adverse manner.


Make a Temporary Heater

Desperate times call for desperate measures. When nothing seems to work out for your fish, you can try making an emergency heater. You will need a candle, sand, tin foil, and a jar.

Melt the candle wax in a bain-marie or double-boiler way. Take a jar and fill it with sand, not more than one-third of it.

Add a wick to the sand and pour the melted wax. Wait for a few minutes for the wax to cool down and turn into a hard substance.

After that, put the jar in the tank. The heat will increase the temperature in the fish tank. For quicker results, you can use tin foil to cover the surface of the aquarium.


Place it in a Warmer Room

Chances are that there are certain rooms or corners in your house that are comparatively warmer. For example, a room where there are no windows might be warmer than the ones that have abundant air coming in.

If you have a smaller tank, it should not be a hassle to carry it to a different place. However, if you have a large tank, it might not be the most convenient option.

Regardless, try to keep the tank in a warmer space. If you live in a two-story house, the room on the upper floor will be warmer. You can try keeping your fish tank in such places to avoid getting the temperature reduced.


Complementary Ways to Keep a Fish Tank Warmer Without a Heater

Besides finding fish tank heater alterations, certain methods can help you keep your fishes at their suitable temperature in the absence of a heater. They are as follows:



If you want your fish to survive without a heater (for a short period), you need to alter their diet. You will have to significantly reduce their diet to decrease their ammonia output.

Oftentimes, the fishes’ metabolism will drastically slow down at a cool temperature that can work in your favor. Keep this in mind while feeding them. Give them their food in smaller proportions to maintain the sanctity of the tank.


Quality of Water

Quality of Water

Except for the water temperature, you will also have to focus on the quality of the water. In case there is a power shortage, your filtration system will not work either. In such a situation, you must check the water quality regularly.

If you feel that the tank needs a water change due to its deteriorating water quality, it needs to be done according to the desired water temperature.

Boil some portion of the new tank water and add it to the regular water. Avoid adding the boiling water directly to the tank. This will have negative consequences on your fish.


Things You Need to Keep Handy

Power outage waits for nobody and your fish tank heater could give up in the middle of the night. So, it is necessary to have an assortment of things ready in case the situation strikes.

  • A thermometer to check the temperature of the water.
  • Blankets, towels, lids, etc. to cover up the aquarium.
  • Leak-proof containers
  • Candles or stove to heat the water.



Which fishes need a water tank heater?

If you are a fan of tropical fish, you will require a heater. Tropical fishes like Betta, Flower Horn, Freshwater angelfish need heated environments to survive. The ideal temperature is considered to be 78F.


How long will tropical fish survive without a heater?

As there are different kinds of fish, it has a wide spectrum. However, generally, tropical fishes can survive up to 12 hours without a heater.


Which fishes are less susceptible or responsive to the change in temperature?

Certain species hold the power of surviving for a long period in the absence of a fish tank heater. Not only can they tolerate the dip in the temperature, but can also endure poor water quality.

Some of those fishes are goldfishes, zebrafishes, etc. Such fishes are sturdier and can survive effortlessly in less indoor room temperatures.


Can bettas die from cold water?

Tropical fishes like bettas can die from cold water as it slows down their immune system and makes them prone to diseases. On the other hand, hot water can make them age quickly with the increase in their metabolism rate. So, the fish tanks are supposed to have a temperature that is neither too cold nor too hot. A balance should be maintained in the temperature for the betta fishes to survive.


Can I add warm water to a fish tank?

In case the water heater fails to function, you need to come up with different solutions to maintain the temperature in the fish tank. This can be done by adding warm water to the tank.

Many people believe that adding hot or boiling water to the tank can do the trick but it not so. You must never directly add hot water to the fish tank. This can damage some of the fishes who are not accustomed to such heat.

You can add the water in two ways. Firstly, you can boil some water and add it to a leak-proof container. Place the container in the center of the tank and you will see the temperature increasing.

Secondly, you can take out some tank water in a container. Add the boiling water to it till you reach a balanced temperature. After that, slowly add the water to the tank.


Can betta survive in tap water?

Tap water is the top-most choice when it comes to betta fishes. This kind of fish thrives in water with a neutral pH of around 7.0 As tap water has a pH of 6.5-7.5, it makes it an ideal choice for betta fishes.


How long can a betta live in unfiltered water?

Bettas require both-a heater as well as a filter. As they cannot survive without it, bettas shouldn’t be kept in unfiltered water. If they are given the right amount of care, they can easily survive for three to four years.


Also Read:

2 Ways to Lower Alkalinity in Reef Tank



We hope that as we are coming to the end of the article, you are now aware of some of the possible techniques. If the aforementioned methods are used in the right manner, you can keep your fish water tank warm even in the absence of a heater.

As tropical or betta fishes are special kinds of fishes, it is crucial to take some extra steps and efforts in giving them a suitable environment. Provide the right care and ensure that your fishes get the essential living conditions.

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