How to Heat Up Fish Tank Water Quickly? – Top-tier Tips

Tank water temperature is an essential factor that fish owners must pay attention to since it can severely affect the pets’ health status (especially their metabolisms or respiratory system).

Therefore, it’s vital to warm up a fish tank ASAP once the overall temperature drops. No more beating around the bush, I’ll show you 6 easy solutions on how to heat up fish tank water quickly.

Ways to Heat Up Fish Tank Water Quickly

#1 Get A Tank Heater


This solution is very simple since all you need is a decent tank heating system. These devices will automatically maintain water temperature in fish tank by monitoring abrupt temperature changes and fixing it instantly.

The 4 most popular kinds of heaters you can refer to are: submersible heaters, immersible heaters, filter heaters and substrate heaters.

Remember to read the users’ guideline carefully and choose an appropriate one depending on the tank size/volume of water, your room’s average temperature and the types of fish.

For example, with each gallon of water, your heaters should have 3 to 5 watts. Based on that, a 300 watts heater might be able to retain the normal temperature inside 200-gallon tanks.

#2 Use Heating Pads/Mats (Or Under Tank Heaters)


Just like the previous suggestion, this option isn’t complicated and you only need to place a heating pad underneath your fish tank. These tools look like a big, flat, electrical sticker made of metal/plastic and here are the suggested steps to employ them:

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  • Remove the paper wrap/cover and reveal the adhesive layer.
  • Start to stick an edge of the “sticker” onto the bottom of your glass tank and slowly slide the rest of the pad there.
  • Recheck and ensure that the whole thing contacts your tank perfectly, especially the space near the power cord.
  • Adjust the heating pad’s temperature to low and watch how it works for a time.


Using heating pads is not a regular way to heat up aquarium water, but it truly works. Yet, you need to be careful and make sure that the tool doesn’t become too cold/hot or you will kill your pets.

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  • Freely use the heating mat for fish bowls and for a 5 gallon fish tank (or even with the smaller tank sizes) if you cannot find an appropriate heater for them.


#3 Use A Hot Water Bottle


I wouldn’t highly recommend this trick, but you can utilize it in emergent situations as it’s extremely easy and works pretty fine without power.

To prepare, you will need a bottle of hot water. After that, taking advantage of the principle of temperature balance, the heat from the water inside the bottle will increase the warmth of aquarium water.

#4 Change Tank Water Gradually With Warmer Water

This technique is similar to the one given before, except instead of using a plastic container, you will add warm water to a fish tank. However, do not pour boiling water right into the tank – it’s safer to start by slowly adding warm water in.

Keep an eye on the temperature of the overall tank water during the procedure and stop when it reaches the desired temperature.

#5 Move Your Fish Tank To A Warmer Spots


Now, lift your fish tank up and move it to somewhere warmer in your house (such as inside the kitchen, under direct sunlight or nearby the fireplace) and let everything work on its own.

Just don’t forget to pay attention to the temperature changes to make sure the water doesn’t get too hot, extreme heat can kill your fish.

Note: Did you realize that placing your fish tank near cold spaces such as windows or open areas will force your heater to overwork? If not, try not to place your fish tank in a cold room thereafter and keep your tank warm without electricity waste.

#6 Utilize The External Environment’s Temperature


Simply use the house/room thermostat anytime the weather cools down and affects your fish’s living conditions. As a bridging effect, raising the general temperature of the space will also increase the temperature inside your tank.

However, a larger tank, such as a 20-gallon tank, will always heat up slower than a little, 3-gallon fish tank. As a result, if you just need to heat water in small tanks, I highly recommend this technique.

Several Ways To Keep Fish Tank Warm

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  • Check your tank water’s temperature with a thermometer frequently.
  • Utilize the lighting system as the brightness from light usually provides a warming effect.
  • Use insulating sheets such as foam, paper, warm blankets, aluminum foil, or fiberglass to keep the temperature within your fish tank stable without a heater.This tip will be especially helpful when there are external climate changes or power outages.
  • Always put the tank lid on to partly insulate your water surface with cool air above, which might lower the tank temperature.
  • Try raising your fish in a comfortable yet smaller tank. This way can minimize the possible sudden changes in the tank water’s water and reduce the pressure on the heater.



What type of heaters are used for fish tanks?

As mentioned above, 4 main types specially used for fish tanks are submersible/immersible heaters, filter heaters and substrate heaters. You might find heating mats/pads also useful in this case, but people usually employ it for their terrarium.

What is the best way to warm up betta tank?

All of the previously suggested methods work with betta tanks but some of them work better in different situations. For instance, while a tank heater works best in a larger tank, heating mats perform perfectly as a fish bowl warmer.

An additional tip for you here is whenever temperature becomes lower than usual, bettas tend to skip eating, swim extremely slowly and move to the bottom of the tank. At that time, you should think of a solution to fix things up.

Why do you need to keep a fish tank warm?

Fish cannot generate their body temperature themselves so any fluctuations (such as temperature) can directly affect their health (from the immune system to the digestive system).

However, the temperature required for your fish tank depends on the fish you have, I highly recommend maintaining it around 23 to 27 degrees C (or 75 to 80 degrees F). Things might be different between coldwater (which doesn’t really need heater in tanks) and tropical fish.

How long does it take for a fish tank to heat up?

Regularly, it might take 24 to 48 hours for a heater to heat up your tank (depending on tank size and types of heater). In case you want the effect to be significantly quicker, try the technique with a hot water bottle above. It goes the same if you want to warm up a betta fish tank.


Have you found the best answer for your question of “how to heat up fish tank water quickly” or “how long does it take for an aquarium to heat up” yet? I hope that you will find my provided information above helpful.

If you have any other tips or solutions to fix this issue, feel free to raise them up and we can discuss them together. Thanks a lot in advance!