How to Keep a Fish Tank Warm Without a Heater? – 4 Tips

how to keep a fish tank warm without a heater

Owning fishes as a hobby or a business is a lot of work. True, it can be very fulfilling, but not without some bumps on the road. Some of the most riveting scenarios are having your filtering system broken or your aquarium heater snap.

As fish require a supplementary heating system to maintain their ideal body temperature, a sturdy and quality heater is a must.

How to heat a fish tank without a heater may make you scratch your head, but with the following tips below, you will know exactly what to do next.

Learn the top tips on how to keep a fish tank warm without a heater and have your business up and running without any problems.

Ways to Keep a Fish Tank Warm Without a Heater

The health of tank fish depends on the quality of water, food, and temperature they get and are maintained. Tank water temperature affects the oxygen levels and bacterial population surrounding your fish. Keeping your tank with a heater is a requisite you shouldn’t skip.

However, in cases where your tank heater is damaged and may need a long time to repair, fret not, there are still ways to warm a fish tank without a heater.

But first, what are the tools you need to prepare?

  1. Thermometer – A thermometer should be at the top of your list. You need a quality one to keep track of your water temperature changes and to be easily notified when there’s a drastic drop or increase. Pick the thermometer with an average temperature range.
  2. Lights and hoods – Lights and hoods can contribute to warming tanks. A hood also helps prevent too much water from evaporating while increasing the tank’s humidity at the same time.
  3. Filters – A good filtering system can save you a lot of trouble. You can opt for a biologic filter as a cost-effective choice. This helps avoid ammonia and excess fish food to soil the quality of water in the tank that could consequently contribute to the possible erratic temperature changes.
  4. A nano tank – Picking a small-sized tank that can accommodate your fish can reduce the stress of keeping the water warm enough with a heater.

These small tanks are often referred to as nano tanks. They can heat up fish tank water quickly and maintain water temperature in fish tank more easily.

Once you’re all set, you can employ the following tips on how to heat a fish tank without a heater:

1. Transfer your fishes to a smaller tank


The cheapest way to heat aquarium without a heater is to transfer your fish to a smaller tank. The science behind it is that with lesser area to occupy, the greater the transfer of energy and heat.

Make sure you leave enough space for your fish to swim around without getting stressed or aggressive toward each other.

2. Position your fish tanks near your home’s warm spots


It’s easy for your tank to change temperature, especially when in power outage and when placed in a cold room. To minimize the damage brought about by this change, it is best to position your fish tanks near your home’s warm spots.

If you live in a 2-story building, transfer your aquarium upstairs since higher-level areas tend to be warmer. Also, pick a space where the sun rays in the morning can reach it. This will keep the tank heated better without a heater.

3. Add warm water to a fish tank


You can also gradually heat up your aquarium by adding warm water to your fish tank. Do this in an incremental amount and not all at once, as it may put your fish in danger.

You can also put a hot water pack and let it float on top of your tanks until your tank water gradually heats up and keeps the fish warm.

4. Use a fish bowl heating pad


Without non electric fish tank heaters, heating pads are an affordable choice for your fish. In addition to heating up your aquarium, heating pads can help protect your tanks from any breakage or damage.

Which Fish Species Are Most Affected by Changes in Water Temperature?

Fishes are categorized as coldwater, cool water, or warm water fish. Some are even in between each category. Among the coldwater fishes are brook and rainbow trout. Fallfish and Northern Pike belong to the cool water fishes, while bluegill and shiners are warm water ones.

Increasing water temperature, as experienced with climate change, affects the cold and cool water species most. In a home setup, it is important to acclimate your fish to the right environment where they can thrive. If there are changes to their used to water temperature, it should only be minimal.

What is the Ideal Temperature for Each Fish?

As a general rule, figure out which type of fish you are housing then study the range of water temperature where they thrive best in order to provide the maximum care for them.

[su_table responsive=”yes” fixed=”yes” class=”productable”]

Type of FishTolerated Water Temperature
Tetras75° -80°F
Brook Trout and Longnose Dace68° – 77°F
Goldfish68° -74° F
Bluegill and Carp65° – 80°F
Discus82° – 86°F
Angels78°- 84°F
Cichlids76° – 82°F
Guppies72 ° – 82°F
Betta fish75°- 80° F
Rainbowfish74° – 78° F


Helpful Tips/FAQs

What is the ideal water temperature in an aquarium?

There is no hard or fast rule when it comes to water temperature adjustments. However, it is best to keep it between 75°-80°F (24-27°C). Sustainable pH should also need to be within the range of 6-8.

How long can a fish tank go without a heater?

In general, a fish can only go up to two days without a heater. As fish are cold-blooded animals, they need heat to thrive.

Keeping them in a warm environment suitable for their health is best to keep them alive, even without a heater or in moments without electricity. Heating mat for fish bowl can also provide the necessary heat for them.


Having your heater broken down can cause you this huge anxiety you can’t shake away. However, not all is lost as there are still alternative ways to maintain water temperature in fish tank without it.

The given tips above on how to keep a fish tank warm without a heater has proven to be effective in providing a conducive environment for your fishes to thrive and stay healthy. You can refer to our table to keep your betta fish warm.