A Complete Guide To Heating Your Bettas Tank

Last Updated on 2023-12-22

If you’ve just bought an aquarium you may be wondering do betta fish need a heater?

If you’re on the fence about buying a heater then after reading this article you’re going to find out:

  • The optimal temperature your betta fish thrive in.
  • Why temperature fluctuations are so dangerous.
  • The fatal consequences of water that is too cold.
  • How you can keep your tank warm if your heater breaks.

You can skip to any information you want using the links below!

Do Betta Fish Need A Heater?

You may have seen the pictures of bettas in tiny fish bowls or sometimes cups. And you may be questioning whether bettas need a heater or not. Well, bettas come from a tropical climate, so you can probably guess the answer yourself.

It’s essential to make sure your betta fish has a heater. Not only will it keep the temperature in the tank warm enough, it will also keep it warm CONSISTENTLY. Which is vital for avoiding temperature shock which can become fatal fast.

In fact, one study found that the best way to increase your bettas lifespan is to not only make sure they’re in a big enough tank, to also ensure that the tank is being heated enough!

How Important Is A Heater For Bettas?

If you don’t have a heater for your betta then you should buy one ASAP. All fish are extremely sensitive to the temperature in their tank, and in particular, constant fluctuations. While a cold wind or draft may be a nuisance to you, over time they can prove fatal to your betta. In fact, avoiding temperature shock is one of the best things you can do to keep your fish healthy.

The only time you can get by without a heater is if the room your tank is in remains at a constant temperature. You may think your room does this. But have you taken into consideration that the temperature of your house drops at night, and in the winter?

Heaters for your fish tank aren’t expensive and they’re well worth the investment to keep your betta healthy.

do bettas need a heater infographic

What’s The Ideal Temperature For Bettas?

The ideal temperature range in a betta tank is 78-80°F. This is the temperature that is going to help keep your betta in optimum health. However, bettas will remain healthy anywhere between 76-82°F. The danger comes when your temperature becomes too low or too high.

If the temperature of your tank drops below 74°F or goes above 85°F then it’s going to severely impact your betta’s health.

Most tropical fish are going to fit somewhere nicely in between these two wider temperatures as well.


What Will Happen If Your Betta Gets Too Cold?

When your betta is in water that is below 74°F you’re going to cause them serious distress and eventually they will die.

The first thing you will notice when your tanks temperature begins to drop is your betta becoming sluggish. This is because his metabolism is slowing down as he tries to conserve energy.

As your betta increasingly becomes more stressed you’ll notice him stop eating. The whole time this is happening his immune system is also weakening because of the added stress on his body.

You’ll begin to notice the color fading from his skin and scales.

He may try to stay near the bottom of the tank or where any heat is.

But, it won’t help. Now that his immune system is low he’ll be more prone to a bacterial or fungal infection.

Some of the diseases and bacterial infections such as fin rot will be relatively easy to cure if you get the temperature back up and follow a proper care guide, like the one you can find here. Or they could get a disease which is more serious like dropsy.

As you can see, leaving your betta in a tank that full of cold water is extremely cruel. And if your not 100% certain you can maintain a constant water temperature without a heater then you need to get one.

betta fish

What Will Happen If A Betta Gets Too Hot?

If you’re curious about what will happen when a betta gets too hot, then the truth is over 85°F your betta will slowly begin to start overheating.

The first signs you’ll notice is your fish swimming erratically. Fish are cold-blooded animals and can only stay at the same temperature as their surroundings. The added heat will give them more energy. This sounds like a positive but actually, it will cause your fish massive stress weakening their immune system.

If you’re tank is getting too hot there are solutions. One thing you can do is let a fan blow over the top of the water. This is going to cause evaporation to happen at a faster rate keeping your tank colder.

And remember, in smaller tanks, it won’t take much for the tank to overheat. In fact, even direct sunlight, on a small tank can heat it up rapidly.

Why Does the Water Temperature Need To Stay the Same for Betta? 

When there are fluctuations in water temperature it can cause damage to the your bettas immune system and affect their metabolism. Some of the problems that changes in a betta fish’ water temperature will produce are:

Temperature Shock

In extreme water temperatures, Betta fish will suffer from bouts of temperature shock that could lead to lethargy, coma, and possible death. 

(Find out more about temperature shock in bettas.) 

Changes in Metabolic Activity 

As Betta fish water temperature changes, the fish’s body temperature will also change. In cold temperatures, a Betta’s body will become cold, causing lethargy and a loss of appetite in your betta.

On the other hand, water temperature that is too warm can increase metabolic activity in the fish and cause the fish to become hyperactive.

Hyperactivity stresses your betta and affects their overall health and can eventually lead to energy burnout.

These sudden swings from hot too cold will eventually wreak havoc on your betta.

Respiration Problems 

As the water temperature increases or decreases, the availability of oxygen also changes. Any changes in water temperature inversely affect oxygen levels.

As previously mentioned, under hot water temperatures, oxygen levels drop dramatically, and betta fish swim to the surface in search of oxygen. The absence of oxygen will hamper their respiration process, which in turn damages the metabolic rate. 

Immune system 

The effects of changes in water temperatures will also harm your bettas immune system. Extreme water temperatures propel or even induce the birth of certain bacteria and parasites in water.

As a result, Betta fish will fall sick more often. Gradually as the strength of the immune system declines, your betta will be exposed to more and more diseases.


A weakened immune system due to changing water temperatures struggles to combat possible infections and diseases. One of the most common illnesses affecting Betta fish is Fin Rot.

This condition causes bacteria to feed upon the fins of your Betta and and if left untreated will rot their fins down to their body.

Apart from bacterial diseases, many parasites induce mild to severe infections on Betta fish. Other than external diseases and parasites, your Betta fish may also suffer from internal problems such as constipation and a loss of appetite.

How to Maintain a Constant Temperature 

As you can see, maintaining the ideal betta temperature is vital so here are some steps you can take to ensure that betta fish stays within their temperature range.  

Tools for Temperature Monitoring– Use a high-quality thermometer. – Don’t rely solely on the tank’s thermostat; invest in a reliable external thermometer.
Heating the Tank– Invest in a good heater to maintain water temperature. – Follow the rule of thumb: about 5 watts per gallon of water. – Avoid cheap heaters to prevent the risk of water overheating.
Changing Water Gradually– During water changes, ensure the temperature doesn’t change abruptly. – Add water of a similar temperature to maintain consistency. – Aim for a gradual partial water change, ideally 5-10%, to avoid inducing significant temperature fluctuations.
Tank Placement for Stability– Keep the tank away from windows and doors to avoid external temperature fluctuations. – Ensure the ambient temperature around the tank remains stable for consistent water temperature.
Emergency Heating Methods– If the tank heater malfunctions, wrap the tank in blankets to retain heat. – Place a hot water bottle in the towels for additional warmth. – Use tealight candles in a safe manner to help maintain heat. – Consider other emergency heating sources to prevent a sudden drop in temperature.

What Size Heater Should You Get For Your Betta’s Tank?

To ensure there is warm water in your bettas tank at all times, you should choose a heater that has 5 watts of power per gallon of water. For example, a 10 gallon tank will need a 50 watt heater, a 15 gallon tank will need a 75 watt heater and so on.

I’ve found that when you get to much larger tanks, a good idea is to simply add more than one filter to the tank. They won’t overheat the tank, as once the desired temperature is reached, they’ll just turn off.

Why You Should Consider Getting A Bigger Tank

If you had a cup of boiling water or a bath of boiling water, what one would cool down first?

Obviously, the temperature of the cup would drop a lot quicker than the baths. And that’s the exact same reason you should consider a good size tank.

Even though the recommended minimum for bettas is 2.5 gallons, a smaller tank is more susceptible to faster, drastic temperature changes. (And they also need to be cleaned more regularly.) I personally would never go any lower than 5 gallons for a betta.

Once you start to get tanks that are 5 gallons or higher, it’s a lot easier for the tank water to stay at a constant temperature. Even if you have an aquarium heater in a 2.5-gallon tank a sudden drop in room temperature is still going to have a big effect on it.

What Are The Different Heaters For Your Aquarium?

Before you go out and buy a heater for your aquarium, there are a number of different heater types you can choose from. Here are the four types of aquarium heaters:

Type of HeaterDescriptionAttachment MethodProsCons
Immersible HeatersHeating element in a glass tube, partially submerged. Control knob above water.Mounted at the top with a bracket.Easy to control temperature.Affected by room temperature. Temperamental.
Submersible HeatersFully submerged in the aquarium.Suction cups to aquarium glass.Consistent heating. Unaffected by room temperature.Risk of breaking if left out of water.
Substrate HeatersLocated under the substrate, ideal for planted aquariums.N/AEncourages plant root growth.Not commonly used for betta tanks.
Filter (In-line) HeatersAttached to the external filtration system.N/AEven heat distribution. Good for large tanks.Stops working if the filter stops.

Immersion Heaters

Immersible heaters, or “hang-on” heaters, have a heating element inside a glass tube, submerged in the aquarium water, with an external control knob. They mount at the aquarium’s top via a bracket but are sensitive to room temperature fluctuations. These heaters generally eschew suction cups for mounting.

Though not the most popular due to their temperamental nature, immersible heaters can be an option. However, I suggest opting for:

Submersible Heaters

Fully submersible, these heaters attach to aquarium glass with suction cups, in horizontal or vertical positions. They offer consistent heating, unaffected by room temperature, but require monitoring to prevent damage when water levels drop. Reliable for stable temperatures, This is the heater I currently use:

Fluval M50 Ultra-Slim Submersible Aquarium Heater – 50W Underwater Heater for Aquariums up to 15 Gal.
  • Modern Aesthetic: M-Series heaters combine modern aesthetics with reliable Italian construction. Employing an ultra-slim profile, these heaters are a welcome departure from traditional, bulkier designs.

Substrate Heaters

Used in planted aquariums, substrate heaters sit under the substrate, enhancing plant growth by warming the substrate and circulating water. While not common for betta tanks, they’re beneficial for planted setups.

Filter Heaters

In-line or filter heaters attach to external filters, heating water as it circulates through the filter, perfect for larger or multi-fish tanks. However, they depend on filter function, so if the filter fails, so does the heater, which can be risky.

While my preference is for submersible heaters, assess your needs to choose the right one.

Do betta fish need a heater

How to Heat a Betta Fish Tank in an Emergency

If you have a heater for your fish tank, at some point there may be an emergency. The heater might break or there could be a power cut. Whatever it is, when the times come you may be wondering how you can keep your tank warm.

Once again having a bigger tank will benefit you in this situation. The water will take longer to cool down, giving you more time to come up with a solution. Some common solutions are:

  1. Turning up the heating in your house. This can work if you know it won’t be long before you can heat your tank again, or if you’re using a small tank. By heating your house, you’re going to stop the room temperature lowering the water temperature.
  2. Make sure you move your tank away from any windows and get it closer to the center of your house. Heat is lost through windows, so areas of your house near windows can often be cooler.
  3. However, if it’s a sunny day, and quite warm outside you might consider doing the opposite. Leaving your tank in the sun is going to heat the water up. Just make sure it doesn’t get too hot.
  4. Get some hot water and place it in a bag. (10% of the size of your tank should be enough). Make sure the bag is warm but not boiling. Take 10% of the water out of your aquarium and place the bag in. Then just let the bag float on the top of your tank.
  5. If your tank is open topped then you can place a towel over the top to help keep the heat in. This can also keep heat in when you do have a lid. Heat rises, and putting a towel over your tank is going to keep the heat in.
  6. On the subject of towels, you can also wrap towels around your tank to keep the heat in as well. While the sudden light change may stress your betta a little, it’s still not going to be as stressful as a water temperature drop.
  7. Try using other household items that create heat. For example, you could move a lamp near your tank and focus light on it, or you could aim a hairdryer at your tank. Obviously, these are short term solutions but they can be useful while you’re looking for a more permanent solution.
  8. Another great choice if your heater has broken is to wrap your tank in an electric blanket. Just make sure you’re monitoring the temperature of your tank carefully.
  9. Set up candles around your tank. Tea lights work best. If you put enough around your tank, the heat from the flames is going to be enough to keep the water in your tank warm.

These are just some of the ideas I’ve come up with off the top of my head. If you have any ideas you should try them too. The most important thing is to make sure you’re monitoring the temperature of your tank and making sure that it’s not rising or falling to significantly.

How Long Will A Betta Survive Without A Heater?

There are so many different factors that go into whether a betta can survive without a heater. For example, if the temperature of your room is above 78°F then your betta is probably going to last a long time. But if it’s too cold or your betta is already sick then it can be a matter of days before your betta becomes extremely unhealthy. But once again there are so many factors that should be taken into consideration such as room temperature, the age of your betta, how healthy your betta is, how quickly the water temperature is dropping etc.

To master the art of betta fish care, you need a comprehensive guide. Click here to read one!

What Else Should Your Betta’s Tank Have?

As well as a heater, filters and thermometers are also essential for your bettas health.

A thermometer will simply allow you to check that the water is the temperature it should be so you know everything is alright. A filter, however, is much more essential.

Filters are going to create a place for beneficial bacteria to live. This bacteria will keep the ammonia, nitrite, and nitrate levels in the aquarium water low, improving the water quality.


Here are some frequently asked questions that people have about the perfect water temperature for their betta.

Is 70F Too Cold For Bettas?

70°F is way too cold for bettas. These tropical fish need warmth to thrive, so the colder it gets, the slower and weaker they become, which puts them in danger of infection. Keep your betta’s tank temp between 75°F and 80°F to keep them happy and healthy!

Is 24C Ok For Bettas?

Bettas do great in temperatures between 24-27°C (75-80°F), so the 24°C mark is where they’re happiest. That way, they can live a long, healthy life and stay pleasant and stress-free.

Is 84F Too Hot For Betta?

Keep the water in your betta tank on the cool side – 84°F is too warm for them. If the temperature creeps up, you’ll probably see signs of distress from your betta fish. So keep the water cool!

Do Male And Female Bettas Need The Same Temperature?

There is no difference between a male and females bettas temperature needs. Both thrive best in temperatures as close to 78°F as possible.

Do You Have A Better Understanding Now?

So, do betta fish need a heater?

After reading this article you should have a better understanding of why it’s so important for your betta fish to have a heater. Just as a quick reminder here are the most important things you need to know.

  • The ideal temperature for betta fish is between 78-80°F. This is the temperature in which they will really thrive. However, if your tanks temperature is between 74-85°F they will still stay healthy.
  • When the temperature of your tank drops below 74°F then your fish will start to suffer. His immune system will weaken and the most likely outcome will be a disease and then death.
  • If your tank goes over 85°F then your fish will start overheating, causing stress and eventually death.
  • One of the best ways you can keep your fish tank at a stable temperature is to get a bigger one (minimum of 5 gallons). When there’s more water in a tank it’s harder for the temperature to fluctuate as much.
  • If your heater breaks there are a number of things you can do to keep it warm. Such as floating a bag of hot water in it, wrapping it in an electric blanket and moving it somewhere warmer.
  • If your heater does break it doesn’t mean your betta will get sick straight away. There are a lot of factors that will also contribute such as age and the current strength of your bettas immune system.
Do Betta Fish Need a Heater
Ultimate Betta Fish Care Guide
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Hey! I'm Nicolas from Iguane Media !

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