Betta Fish Temperature: How Warm Should the Water Be?

Betta fish come from the tropical regions in Southeast Asia such as Thailand and Burma. It should therefore be no surprise that betta fish require warm water if they are to thrive in captivity.

Your betta fish tank temperature should sit within a very narrow range of 78 – 80’F – that’s 25.5 – 26.5’C.

A few degrees either side shouldn’t do your fish any harm, but try to ensure that the water in your betta tank doesn’t move too far away from these optimum figures.

Fortunately when you apply the following tips it becomes simplicity itself to provide your betta fish with the perfect temperature…

Do You Need a Heater for a Betta Fish?

Almost without exception betta fish require a heater if they are to remain fit and healthy. Trying to keep your betta fish warm without a heater is fraught with difficulties.

The reason for these difficulties is that betta fish dislike sudden changes in water temperature, which are more likely when an aquarium heater isn’t used. Ultimately this sort of stress can shorten the lifespan of your betta fish.

It is important to note that even those of us lucky enough to live in a very warm area should still consider using an aquarium heater. The reason is that most modern betta tank heaters incorporate a thermostat which continually monitors the water temperature.

When the temperature drops below the level you have specified it kicks in, helping to keep the water temperature a nice even, steady temperature. This, in turn, keeps your fish happy.

So even if you’re lucky enough to live in Arizona, and enjoy hot summers, then it is still important to monitor the water temperature to ensure it is suitable. In a minority of cases you may instead need to consider an aquarium cooler to prevent your fish tank from actually overheating at the height of the summer.  

Maintaining the Water Temperature in Your Betta Fish Tank

We know that the right water temperature is important for your betta fish. But how do you achieve this in the most effective way possible?

Buy a Large Betta Fish Tank

Different materials heat up and cool down at varying rates. Water, for example, tends to rapidly get cold. This is something we’ve all experienced after forgetting about a cup of coffee we brewed.

When it comes to betta fish care a central principle is trying to control these variations in water temperature, to maintain a steady environment for your fish.

Larger volumes of water heat up and cool down more slowly than smaller volumes. This means that it is easier to maintain a suitable ongoing temperature for your betta fish in a larger tank.

For betta fish a tank of no less than 5 gallons should be used. If you can afford one, a 10+ gallon tank is likely to be even more suitable.

Invest in a High Quality Aquarium Heater

There are hundreds of different aquarium heaters on the market. As the right water temperature is so important it’s worth taking your time to find the right heater to start off with.

Some elements you should consider before making a purchase are:

Is it suitable for my aquarium size?

There are actually two considerations when it comes to size. Firstly, will the heater you’re considering actually fit comfortably into your betta fish tank?

Many heaters are quite long, while betta fish tanks can be relatively small when compared to standard tropical community fish setups.

The second consideration is whether the heater is closely matched to the volume of water you’ll be placing in your tank.

Be mindful that different heaters are designed for different water volumes, and choosing a heater that is too powerful for your tank can lead to sudden, extreme changes in water temperature.

Does it have a built-in thermostat?

Having an aquarium heater alone isn’t enough; you’ll also need a thermostat that monitors the water temperature and turns the heater on and off automatically.

In truth, most betta fish heaters do come with a thermostat built in – but not all. So take care to check that any aquarium heater you consider states clearly that it includes a thermostat.

How easy is it to change the temperature?

Just because you set the temperature at 80’F doesn’t necessarily mean that’s how warm the water will be. Aquarium heaters are notorious for being a few degrees out; even the high-end models.

After installing your heater it’s entirely possible that you’ll need to turn it up or down a few notches to reach that optimum temperature.

Any aquarium heater that makes this easy can make your life a lot easier. For example, a handful of modern heaters have a temperature controller on the electrical flex, so you don’t need to stick your hand into the aquarium water to modify the temperature.

What do other owners have to say?

Lastly don’t just listen to what the marketing departments of these heater manufacturers have to say. It’s worth investing some time into researching your heater thoroughly. Look for reviews such as on Amazon.

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Ask on discussion forums or seek guidance from friends on social media. Once you’ve gathered some unbiased feedback you’ll be in a much better position to entrust your fishes health to one specific heater.  

Install an Aquarium Thermometer

We’ve already discussed that aquarium thermostats aren’t always 100% accurate.

A further potential issue is that of course aquarium heaters – like any electrical equipment – can malfunction. The sooner you spot the problem and resolve it the better. I therefore like to employ two different plans to deal with such situations.

Firstly, invest in a good quality aquarium thermometer and record the temperature regularly. This allows you to double-check on the water temperature, and to make any changes needed to the thermostat. Of course, if your betta fish tank heater stops working you’ll also identify the issue much more quickly.

Secondly, like many other fish keepers, I actually keep a spare aquarium heater in the cabinet under my fish. In this way, should a heater fail late at night, or on a Sunday, I can quickly swap it over without a second thought.

Get Your Tank Positioning Right

A wide variety of environmental factors can impact the temperature of your betta fish tank.

Direct sunlight, for example, can quickly cause your betta fish tank to overheat in the summer. On the other hand, radiators, drafts or external doors can all lead to issues in the winter.

Think carefully about where to position your fish tank to avoid such extremes. Placing your tank in a dark corner away from windows and doors tends to work well.

Monitor Water Chemistry Regularly

Water changes are an integral part of keeping fish as pets. The toxins which build up even in well established aquariums must be removed, and with the water being replaced with fresh.

The issue is that these water changes can greatly impact the temperature in your betta fish tank.

It is smart to invest in a water testing kit (specifically ammonia, nitrites and nitrates) and to regularly check your betta fish tank. In this way you can be certain that you’re carrying out water changes at the correct intervals.

Too often and you’ll be changing the tank temperature more than necessary; too seldom and you’ll need to change far more of the water to obtain the ideal water chemistry figures.

Regular Small Water Changes

When it comes to water changes in your betta fish tank, regular, small water changes tend to be best. As an example, rather than changing half the water each month, try instead doing much smaller changes each weekend.

In this way, the temperature in your aquarium will remain more even over time, reducing stress for your fish.

My Betta Fish Water Temperature is Too Cold

Betta fish need warm water if they are to thrive. While a small drop for a short period of time shouldn’t do your betta fish too much harm, more extreme falls over longer periods of time are certainly a big concern.

If you have noticed that your betta fish tank is too cold then what actions should you take?

Install a suitable aquarium heater

First, the most obvious tip of all: if you don’t have an aquarium heater in your betta fish tank then buy one and get it installed as soon as possible. Even if you only need to use it occasionally it is a small investment for a big return.

Check your aquarium heater

Let’s assume for as moment that you do have an aquarium heater installed in your betta fish tank, yet all the same the temperature is still too low.

The next step is properly checking on your betta fish water heater to ensure that it is installed properly as is working efficiently.

Some things to check:

  • Is the heater actually working at all? Is the water temperature warmer than the air temperature in your home?
  • Is the heater designed for the size of tank you have?
  • Have you tried fiddling with the thermostat to increase the temperature output?
  • Is there tank decor that is preventing the heat from properly circulating around the tank?

Replace your betta fish heater

Assuming you have checked all of the above then it may be simply time to buy a new aquarium heater. As always, be sure to select a well-regarded model that is designed for the size of your betta fish tank.

Add insulation to your tank

If your heater is on and is working well then another option is to consider insulating your betta fish tank better.

In the past I have used tiles made from cork or polystyrene and attached these to the outside of tanks to help them retain heat. Simply stick them to the back and sides of the tank with tape, leaving the front open so that you can still enjoy watching your fish.

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Add a thermal store to your aquarium

Rocks hold warmth much more effectively than water, so adding some additional tank decor can help to keep your aquarium water warmer than before.

Heat the room your tank is in

One final option is to heat the room in which you keep your betta fish. Some keepers opt to use a simple plug-in oil heater to gently warm their fish room, helping to take the edge off any cold weather and allowing their aquarium heater to do a more effective job at raising the temperature.

My Betta Fish Water Temperature is Too Hot

Water that is too hot is just as dangerous for your betta fish as water that is too cold. One reason for this is that the amount of oxygen in your aquarium water varies with temperature; hot water holds less oxygen.

In these circumstances you may find that your betta fish is gulping at the surface trying to obtain the oxygen it needs from the air. Fortunately betta fish are part of a group known as “labyrinth fish” that can breathe air for short periods of time.

All the same, resolving high temperatures is important for the long-term health of your betta fish.

There are a number of ways to cool down your fish tank if the water is getting too hot.

Air conditioning

If you have air conditioning then get this switched on. Stand-alone air conditioning units are available from places like Amazon for very reasonable prices, and these can be an easy and cost-effective way to reduce the temperature in your betta fish room.


Standard home fans can be used to move air around in your betta fish room. Done right, hot air can be blown away, allowing cooler air to reach your betta fish tank.

Control lighting

Sunshine in the summer months can result in rapidly climbing temperatures. To avoid potential problems ensure that your betta fish tank is kept away from direct sunlight. In particularly hot summers consider keeping blinds or drapes closed during the day to keep the heat out.

Consider your aquarium lighting too – if you have it. LED lighting doesn’t tend to get hot, so can be more suitable for lighting a betta fish tank than more traditional bulbs.

Once again, if you suddenly notice that your betta fish tank is too hot then consider turning off any and all aquarium lights so that their heat isn’t making the situation worse.

Aquarium coolers

A huge range of different aquarium coolers and chillers are available, many of them are surprisingly cheap. If you’re having ongoing issues with your betta fish water being too hot then investing in one or more of these cooling fans can be a very wise investment.

Even better, being thermostatically controlled like your water heater, they take much of the hassle of monitoring water temperatures away, allowing you to enjoy your fish once more.

Larger aquarium

Lastly remember that larger fish tanks tend to warm up more slowly and maintain a more even temperature throughout the day. Consequently if you find that your betta aquarium gets too hot on a regular basis then swapping your fish into a larger tank can prove beneficial.

A 10 gallon tank, for example, should remain far more stable than a more traditional 5 gallon aquarium.

Warning: Some fish keepers like to remove the lid of their fish tank when their tank overheats, in the hope that some of that heat will dissipate. This is a very bad idea for betta fish tanks.

Betta fish are surprisingly good jumpers, and so without a sturdy aquarium hood there is a risk that your fish will jump clean out of their water, only to be found some hours later.

One temporary solution is to make or purchase a mesh lid (as can be bought for exotic pets) that can be placed over your betta fish tank – which both allows excellent air circulation but will also prevent your fish from escaping.

Richard Adams

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