4 Signs My Betta Fish Is Cold & What To Do When Problems Come?

Bettas are relatively easy to take care of, making them a beginner-friendly choice for aquarists. However, they are still subject to illnesses and diseases from time to time. One of the most common problems is temperature shock, where bettas experience a change in their body temperature.

If you are wondering “What are the signs my betta fish is cold or hot?”, let’s scroll down and see the answers for yourself!

Detect 4 Signs Of Betta Fish Getting Cold

Bettas are not as active

Unlike mammals, most fish are cold-blooded. This means they cannot generate heat on their own and have to rely on the surrounding environment to keep themselves warm. When the water drops in temperature, bettas inevitably suffer from a cold shock.

As a result, they will find it much more difficult to breathe, move, and swim around. Their metabolism rate will also decrease to adjust the body for further loss of heat, leading to struggles in eating. For the most part, you will see bettas idling around and staying lethargic.

Bettas stay at the bottom of the tank

When bettas do not have enough warmth, they fail to swim as energetically. Thus, it is more common for bettas to hover around the bottom. Sometimes, they will even lay flat down on the floor.

Bettas fall into a coma

If your bettas stop being responsive altogether, chances are they have fallen into a coma. This only happens when the temperature drops to an extremely low point, preventing bettas from pumping oxygen to the brain. When they can no longer control their bodily functions, bettas will lapse.

Bettas get sick frequently

With a limited metabolism rate, bettas are not capable of defending themselves against bacteria and fungus. When their immune system is compromised, coming down with a disease or infection is much more likely.

Even worse, bettas are not equipped to handle these illnesses by themselves. Unless you act promptly, sick bettas with an already low body temperature can slip away quickly.

What Are The Causes Of Betta Temperature Shock?

Bettas are first introduced to the tank

If you drop your bettas into a tank all at once, they are likely to go through a temperature shock. Not only do they have to adjust their bodies to get used to the temperature, but they also need to be mindful of the nitrate level, ammonia level, and pH levels.

It is better if you slowly introduce them to the tank so that they do not feel overwhelmed.

Room temperature changes

betta at the bottom of tank

If your place is experiencing extreme coldness or heat, then the tank’s water will be affected. Whether it becomes colder or hotter, such sudden fluctuations in temperature will be detrimental to your bettas.

Water temperature changes

Every time you change your water, there might be a slight discrepancy in temperature. For example, adding cold water to the tank immediately after emptying the old one sure will be a shock to your bettas.


1. How can I keep my betta fish warm?

Keeping your bettas warm should not be too challenging, providing you follow this advice.

Using a heater helps to ensure the ideal conditions for your tank, even if the room temperature drops.

  • Find a suitable location: Putting your tank near the window or anywhere open increases the chance of a temperature drop. Instead, place it at the corner of the house, where the winds might not reach.
  • Acclimate the fish to the water: When performing a water change, do not replace the old water with the new one on the spot. Heat up the new water slightly and pour it gradually into the tank.

This way, your bettas will have a longer time to familiarize themselves.

  • Seal the heat: If you leave the tank unattended, the heat tends to dissipate quickly. Consider using a lid to cover the top of your tank, moving lamps and other warm objects near the tank, or even floating a bag of hot water inside the water.

This way, your tanks are more likely to remain warm.

2. How long can bettas be in cold?

It depends on how cold the water is. If the temperature drop is not too severe, then bettas may survive up to a few months. However, it should be noted that survival is not at all favorable.

Your bettas will experience difficulties in eating, breathing and generally become too exhausted to move.

3. How can I heat my tank without a heater?

While a heater is the most effective way to heat a tank, there are other alternatives should you fail to afford one.

Firstly, try using a stack of towels. Wrap them carefully around the tank so that they do not block the lights. In case they are not powerful enough, switch to an electric blanket.

But be careful when using the latter. If not moderated, the temperature settings might be too high for your fish.

Secondly, try to take advantage of the open lights in your home. Look for places where the natural sunlights are most rampant. Tilt the tank so it can absorb as much heat as possible.

Thirdly, use household appliances that can emit heat. These include lamps, lightbulbs, candle heaters, and even ovens! Place these items and the water tank in the same vicinity.


Now that you have known about the signs my betta fish is cold, it is time to act on this issue! Check out the fish and look for suspicious symptoms.

If you think they are experiencing a drop in body temperature, do not forget to keep them warm and prevent them from dying early.