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Do Betta Fish Need a Heater? Your Questions Answered

Bettas are some of the hardiest, easily cared for fish in the aquarium trade. Sooner or later we all have a Betta or two; they are just too beautiful and endearing to ignore!

However, many of us are told by well-meaning but wrong pet store employees that these are fish that thrive in bowls without filters, eat plant roots, and need heaters.

Unfortunately, a lot of this isn’t correct, so let’s take some time to understand the needs of Bettas and why they should be kept with a heater!

The Natural Environment of Betta Fish

We are used to seeing Bettas lined up in small bowls on a shelf somewhere, waiting for a nice new home. But what sort of conditions are Bettas found in nature?

As it turns out, they couldn’t be more different! Bettas are the national fish of Thailand, a country famous for its year-round tropical temperatures that bring tourists from around the world. Even in the winter, water temperatures can stay above 75-80℉ in many parts of the country.

These low lying, steamy regions are where you’re most likely to find Betta fish. Shallow ponds and canals quickly get hot in the intense tropical sun. And as you may already know, the warmer the water becomes, the less oxygen it holds.

Add loads of decomposing plant and animal matter to the mix and you have a recipe for severely oxygen-depleted conditions.

Fortunately, Bettas have several adaptations to allow them to thrive in conditions that would kill most other fish. And the most important is their specialized labyrinth organ that allows them to directly breathe atmospheric air. They share this feature with their cousins the Gouramis.

Atmospheric air can hold as much as a hundred times the amount of oxygen as warm water. This way, Bettas can thrive without aeration in even steamy canals and pools.

Do Betta Fish Need a Heater?

Since Bettas are typically in tropical conditions year-round, they absolutely should have a heater to keep them warm. The shallow canals and ponds they live in can change in temperature quickly so Bettas are a lot more tolerant to cold than most tropical fish. But extended cold periods are very bad for their health long-term.

Warm temperatures ensure they maintain a healthy appetite. If your Betta isn’t eating, cold temperatures are one of the most common reasons why they lose their appetite.

Like most fish, Bettas are ectothermic. This means that they rely on the external environment to regulate their metabolisms.

When things are warm, their cells process food and waste efficiently, and your Betta will grow properly. But once things get cold, all of this cellular machinery slows down considerably.

Unlike Goldfish and other temperate fish, Bettas aren’t designed to stay in this temperature zone (60-68℉) for long. Room temperature bowls, with their lack of filters and heaters, are therefore some of the worst conditions for these tropical fish.

When Bettas are kept cold, their digestion slows considerably. Typically, they eat less to compensate, and may even lie on their side on occasion to conserve energy.

Should they ingest too large a meal for colder temperatures, the food may start to rot before it can be properly digested and expelled. This can lead to fatal intestinal bloating in your Betta that’s very hard to treat.

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Antibacterial remedies like Melafix are best as they are broad-spectrum and may save your fish if you act as soon as symptoms arise. But blockages and toxin buildup may cause death within hours, so keep your Bettas warm enough to digest properly!

Bettas kept warm will show increased vigor, wagging their showy fins for their owners and nearby male or females. Healthy males typically engage in building bubble nests as well, in case an enticing mate wanders by!

All of these behaviors slow down or disappear when Bettas are kept too cold. Therefore, we want to aim for 75℉ as a bare minimum, same as for most tropical fish.

In fact, Bettas actually appreciate things even warmer; 78-82℉ is perfect for them. Anything above 85℉ is unnecessary and eventually becomes stressful.

On the warmer side of their ideal range, you’ll help their metabolisms keep infections at bay, digest their food, and encourage breeding behavior in both males and females.

Females are incredibly unlikely to develop eggs in temperatures below 75℉ as this signals that winter is arriving or is already here. Their eggs and fast-growing fry need warm temperatures to develop properly

How Do I Choose a Heater for my Betta?

With the abundance of cheap, efficient electric aquarium heaters on the market, it can sometimes seem overwhelming to choose the right one.

Fortunately, the formula for output relative to tank volume is simple! You want 3-5 watts of power per gallon of aquarium size. And since Bettas are usually kept in smaller tanks, both their power use and initial purchasing price are very reasonable.

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If your room temperature is on the colder side, then go with 5 Watts per gallon to ensure you can buffer the occasional temperature swing. Otherwise, 3 Watts per gallon is usually enough!

Another reason to have a heater is because smaller bodies of water experience temperature swings much faster than larger ones. The reason is simple: they have less heat built up than larger tanks.

A forgotten open window in the winter or other sudden cold shock can easily cause the temperatures in a small bowl or aquarium to plummet.

Keeping My Betta in Cooler Water

I don’t recommend keeping Bettas at temperatures colder than 70-75℉. The colder things get, the more likely they are to get opportunistic infections like Ich and Fin Rot. Their metabolisms simply don’t have the vigor they need to fight off these normally treatable illnesses.

You’ll also see them eat less, move less, and overall become sad, listless fish. We want the best conditions for our pets, not the bare minimum they will tolerate. So invest in an inexpensive, easily installed heater for your small Betta bowl or tank!


As tropical fish, Bettas should be kept at 75-82℉ for optimal health. In their native Thailand, water temperatures can stay in this range year-round. Room temperatures in temperate countries are typically 64-68℉, which is tolerable but too cold for these tropical beauties.

Instead of watching your Betta hang listlessly in cold water, provide a heater. That way, they will perk up, eat with vigor, show improved disease resistance, and even breed once you find a suitable female Betta!

Jason Roberts
About Jason Roberts
Jason is an aquarium fanatic that has been a fish hobbyist for almost three decades.

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