Why is your betta fish laying on the side after the water change? Is it a symptom of a serious illness or just another odd trait of this fish’s personality?

This article will give you the common causes of this condition. So let’s read on to see more!

Why Does Betta Fish Laying on the Side After Water Change?

There are many reasons your betta fish lay on its side after a water change. Here are the most common causes of this:

Older Fish Are Resting at the Bottom of Your Tank

When your betta gets old and lacks energy, it won’t have the strength to swim around the tank.

Therefore, it may lie on its side at the bottom of the tank as a form of rest, which is a harmless cause.

For older fish, we recommend offering more resting areas. Betta fish also love a gentle, slow water flow, which is particularly essential for older fish.

Your Betta Fish is Sleeping

bettas are active during the day and sleep at night

Bettas, like most other animals, also need sleep. They will find a comfortable and safe place at the bottom of your aquarium to lie on their side and take a nap.

Bettas are not nocturnal fish. Like humans, they will be active during the day and sleep at night (or when the room is dark).

These animals prefer to sleep on their side, an exciting feature that further increases their popularity among aquarists.

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Ammonia Poisoning

Chemical changes, including ammonia, may also be responsible for this unusual behavior in bettas.

It is easy to check out for poisoning. You should start by observing your bettas and see if there is any gasping or sign that this fish is breathing heavily.

You can use one of the high-quality aquarium test kits to check the ammonia level. The level of ammonia that you get should be zero or close to zero.

If you find that the ammonia level in the water is too high, a partial water change is essential.

Changing about half of the water in the tank is okay, but we recommend changing about a quarter and repeating the process over the next few days.

Unsuitable Tank Mates

suitable mate for your bettas

Bettas can have aggressive behavior. Although they can coexist with other species in the same aquarium, you will need to choose carefully.

Forget about adding more colorful and bigger fish to your aquarium, as it can intimidate your bettas.

Moreover, an intelligent choice is bottom feeders since they won’t significantly impact bettas.

We recommend avoiding keeping two male bettas in one aquarium as they may fight with each other one day.

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Swim Bladder Disease

This disease is also one of the illnesses for your bettas which is also one of the reasons why they lay on their side.

This condition refers to a fish’s bladder not functioning correctly, making it impossible or difficult for it to swim around your tank.

In this case, your bettas may float near the water’s surface, while others will stay at the bottom.

This disease results from you feeding your bettas too much, or they cannot digest food properly.

The PH Level Is Not Suitable

If your betta is lying on its side at the bottom of your aquarium, it could also be due to poor water quality or an inappropriate pH.

The ideal aquatic environment for bettas usually has a neutral pH of 7.0.

Anything between 6.5 and 7.5 will work well. If the water in your tank has the wrong pH level, it can slowly kill your fish, also known as pH shock.

Temperature Fluctuation

Sudden temperature fluctuations also threaten bettas, which can cause them to stop feeding and lay at the bottom.

In all cases, you should keep the water temperature between 75°F and 80°F.

When water temperature decreases rapidly, your betta fish will experience a cold shock as it is a tropical fish.

It may result in physiological and behavioral consequences, including lethargy.

On the other hand, a hot temperature shock can also keep your bettas from moving, although not as severe as a cold shock.

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Small Fish Tank

Small Fish Tank

Improper aquarium size can also be the culprit. Specifically, it may be too small for your bettas.

Therefore, you need to ensure the size of your aquarium is suitable for the number of fish.

If you keep one betta, your aquarium should hold three to five gallons of water. Of course, if you add fish, you will need to add more water.

Larger aquariums will be very helpful for your bettas as they will receive more space to move around.

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Improper Eating Habits

Providing an inappropriate diet, specifically feeding your bettas too much or too little, can also cause your fish to have this unusual behavior.

If you feed your fish too much, they will get bloated. Just like when we’re full, these bettas tend to stop moving or lie at the bottom of your aquarium.

Feeding your bettas so little that they don’t have enough energy to swim. So they can stop moving and settle at the bottom of your aquarium.


On average, a betta can live two to four years. Its lifespan depends on your care and the conditions of its habitat, including temperature and water quality.

If you want to determine if your betta is dead, observe its gills. It won’t matter if your fish is still breathing, even if it isn’t moving.

When your betta dies, you will also easily notice the discoloration on its body.

It is okay to check your betta by tapping your aquarium to see if it reacts. Even a sick fish will move when the aquarium vibrates.

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Why Is My Betta Fish Hiding After Water Change?

Hiding is a natural behavior for bettas. If your bettas are new to the tank, they may hide all day until they feel safe.

How Long Does It Take Betta Fish To Adjust To A New Tank?

In most cases, bettas will adjust to the new tank within a week.

How Do I Know if My Betta Likes His New Tank?

A happy betta will swim around his tank daily, which signifies that your betta fish likes his new aquarium.

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What Are the Differences Between a Sleeping and Dying Fish?

When you lightly touch your aquarium, the sleeping fish will immediately move, while dying will not.

Alternatively, you can also tell the difference by looking at the gills of your fish. Any sign of breathing will tell you that your fish is not dead.


There are many reasons for your betta fish laying on its side after a water change. It can be harmless, such as your fish being full, sleeping, or old.

However, it can also be a sign that you are taking care of your fish improperly, such as an improper pH level, diet, or Ammonia poisoning.

Thank you for following this post!

Alex is a pet freelance writer and editor with more than 10 years of experience. He attended Colorado State University, where he earned a Bachelor’s degree in Biology, which was where he first got some experience in animal nutrition. After graduating from University, Alex began sharing his knowledge as a freelance writer specializing in pets.

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