Heating Options for Small Betta Fish Tanks

A stable, warm water temperature is important to keep your betta happy and healthy. Keeping a thermometer in your betta’s tank to monitor the temperature on a daily basis is a good idea. The ideal temperature for a betta is 78-80 degrees Fahrenheit (25.5-26.6 degrees Celsius).

Unfortunately having a large heated tank for your betta isn’t always an option. Here are some ideas on how to heat smaller tanks starting at 1-gallon and up.

A few things to keep in mind while heating

1. When heating a small tank, water movement is important. If you can hook up an air stone on a low setting to get some water circulation it will help to evenly distribute the heat.

2. It’s important to monitor your water temperature daily to make sure it is stable and the heater is working properly. Even if your heater has a temperature dial, adjust according to what your thermometer reads in the water instead.

3. During water changes, make sure that the new water is the same temperature as what was previously in the tank so your betta is not shocked by the change.

Small Tank Heating Options

Permanent Heating Option

1. A 25-watt aquarium heater
Many of our members have safely and effectively used 25-watt (or less) heaters in small tanks. Usually “compact” heaters work best because they are shorter in length and easier to the position. A fully submersible heater will also work to your advantage if you have small or angled walls to attach the heater to.

Both of these heaters are popular choices by our members. They are reliable, submersible, and easy to adjust. (Of course, there are many other heater options, so do not feel as though you have to get one of these.)

Hagen Thermal Compact Mini Heater (25-watt): 6” in length, $10+
Hydor Theo Heater (25-watt): shatterproof, 7” in length, $12+

This is an example of a 1-gallon glass tank with the 25-watt Hagen Thermal Compact Mini Heater.

Temporary Heating Options

1. Using a larger tank as the heat source for heating

If you have a larger heated tank and it’s a very temporary thing – you could stick the smaller tank or holding container into the heated tank to keep a warmer temperature. Of course, this would probably work best with a plastic container of some sort that would float at the top. Make sure whatever you use has a cover to keep the heat in and prevent the betta from jumping out. This method would be useful if you need to treat your betta in a smaller hospital tank but have no other way of keeping it warm.

2. The heat from a light

A light of some sort directed onto the water from above the tank. The problem with this is that it does not heat the water equally and the temperature is hard to control. If this is your only option, it can be better than nothing. Be careful when you decide to turn the light off, as you don’t want the temperature of the tank to vary more than a degree or two on a regular basis. Also, bettas need a regular light cycle, so keeping the light on all the time isn’t really an option.

3. If the heater fails or the power goes out

Heat packs that you crack/mix to activate for use in cold weather can be placed on the outside of the tank against the walls to provide warmth. Another option is filling your bathtub up with a bit of warm water and placing the tank in the tub.


In response to the information above, HB forum member supersixone wrote (the forum is no longer available for posting):

I’ve not used them myself, but I know others who have successfully used Hagen Thermal Compact Minis in their smaller tanks.

This is the follow-up to supersixone’s suggestion by Rachel, the HB Administrator:

This is another option that could be used, but like the 7.5-watt Jr. Heaters, there is one slight problem with them that should be noted. These types of heaters are “always on” if they’re plugged in and have no internal thermostat to adjust to varying temperatures.

Most aquarium heaters have a thermostat that will turn it off and on to keep the water at the desired temperature. If you originally set the heater to 78 degrees and the temperature drops it will turn on to heat in short intervals until 78 degrees is reached. If the tank is at 78 degrees already, the heater will remain off.

Basically, the heater will regulate itself to keep the temperature you specify. On the other hand, Jr. Heaters or flat heaters heat to one non-adjustable temperature. How much it will affect your tank temperature is based upon the ambient room temperature. This means that if the room temperature rises or drops so does the temperature of the tank. Ideally, you want to keep your betta’s tank temperature as stable as possible, so if the room temperature will be changing this option may not be the best one.

Also, since there is no way to alter the temperature, it may heat the tank too much and there is no way to adjust it. The flat heater given as an example above says it will raise the temperature up to 5 degrees F in a 2-gallon tank, but it would likely heat a 1-gallon tank higher…and always keep heating at this temperature as long as it’s plugged in.

You’ll want to monitor your tank very closely with a heater of this type to make sure it stays at the appropriate temperature.

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