Why Is My Betta By The Filter?

Your betta will just not come out to swim around like a normal fish. He or she keeps hiding behind or hanging around the filter. What’s going on?

Reasons Why Your Betta is Constantly By the Filter

Bettas hide when they are being bullied by other fish or if they are sick. However, bettas will also stay by water outtake valves or near where the filtered water comes out, in order to breathe better. If your water quality is poor, your betta just can’t get a breath in the water except around where the water is best – right at the filter. 

Your Betta Is Getting Bullied

Bettas are also called Siamese fighting fish for a reason. They have bad attitudes. Even females can be aggressive. Fish are individuals. Some will get along with other fish, and some will not. Some will even become targets of harassment from other fish in the tank.

It is normal for a new betta introduced to a community tank to hide. Learning a whole new environment is stressful enough, without having to deal with new fish.

What’s not normal is if it’s been over two weeks and the betta is still hiding behind the filter. Check to see if the fins are torn or if there are any wounds, which is a usual sign that the betta is being bullied. 

Fish tend to pick a favored hiding place in a tank, especially if there are other fish in the tank. Your betta’s favorite hiding place might be behind part of the filter, such as the intake valve on a hang on the back filter.

If your betta moves around the bottom of the tank and chooses other hiding places, it’s most likely bullying that’s the problem and not being sick or a problem with the water quality.

Your options are:

  • Move the betta to a new tank, perhaps one where he or she can live alone. Bettas do fine by themselves.
  • Take the betta back to where you bought him or her.
  • Test the ammonia levels in the tank to make sure they aren’t elevated. When fish get stressed, they will bully each other.
  • If you have a bottom feeder in the community aquarium, make sure he or she is getting enough food. Bottom feeders like a Plecostomus will suck on the slime coats of other fish when they are hungry.

Your Betta is Sick

Any time a betta (who is not new) hides a lot is cause for concern. Observe your betta for signs of illness. They include:

  • Tiny white spots
  • Fins that seem to be missing in parts
  • Red, purple or brown gills
  • Cloudy eyes
  • No appetite
  • Eyes that seem to be bulging far more than usual
  • Faded coloring (which can also appear when they are scared)
  • Large white spots, as if tiny cotton balls are stuck onto your betta
  • Distended abdomen
  • Fins clamped flat to the body
  • Lying sideways, or otherwise not right side up, on the bottom of the tank.

Treat the betta in the tank or, if in a community tank, remove the betta and place in a hospital tank for treatment. How to treat betta fish for illness varies according to the illness. 

The Water Quality is Poor

Bettas are lucky in that they can both breathe air and breathe in water. If your betta is at the surface of the water gasping, then something is wrong with the water, effectively choking your betta.

Bettas also can get a fresh breath by hanging around the filter, usually where the filtered water comes out. This water is the best quality, so your betta stays where it is most comfortable to breathe.

If you have more than just one betta in the tank and all of the fish are either hanging around the filter or at the surface of the water gasping, then it’s definitely a problem in the water.

Do an immediate partial water change. This will help reduce whatever chemical in the water is bothering the fish. Make sure you stir up some of the gravel with the gravel cleaner to remove piles of poop. You may have to gently move your betta away from the filter so you can get at the piles under the filter.

Ammonia Poisoning

It’s most likely ammonia poisoning. Test your tank water’s ammonia levels. Too much ammonia will kill your fish. A healthy tank should have an ammonia level ideally at zero but at the most 1 ppm (part per million.)

Other signs of ammonia poisoning in fish:

  • Red or purple gills
  • Hanging out near the bottom of the tank (or behind the filter)
  • Lack of energy
  • No appetite.

You’ll need to get a bottle of treatment to remove the ammonia from the tank water. Follow the directions closely.

Do not feed your fish during this time. Decaying food and any more poop will cause the ammonia levels to rise. Chances are, your fish will not want to eat, anyway.

Nitrite Poisoning

If there isn’t any ammonia in the tank, test for nitrites. This is another common chemical that builds up in aquariums to lethal levels. A healthy tank has a nitrite level of zero.

Nitrite poisoning is also called brown blood disease because it will literally turn your betta’s blood brown. This is due to an increase of a chemical in the blood called methemoglobin. Too much of it causes the cells to be unable to use oxygen. The result is that the fish choke to death.

Other signs of nitrite poisoning are the same as for ammonia poisoning, only with these differences:

  • Brown gills instead of red.
  • Gills will move very quickly as your fish labors for breath.

Treatment includes:

  • A 50% water change.
  • Adding a teaspoon of aquarium salt per gallon in the tank. Do NOT use the salt you use on your food. It might seem strange to add salt to a freshwater tank, but it works.
  • Up the aeration in the tank by turning up the flow on your air stone or adding a second air stone.
  • Stop feeding the fish until the tank water tests zero for nitrites. Test every day.

What You Absolutely Do Not Want to Do

You may be tempted to give your tank and the filter a real thorough cleaning after dealing with the troubled water. Resist the temptation. Above all, do not scrub all of the decorations, walls, gravel, and take the filter apart to clean it.

Your fish need beneficial bacteria to keep the water healthy. They do not float around in the water but need to live on surfaces of things – like the decorations, the walls, the gravel, and the filter. Especially the filter.

So, Why Is My Betta Fish By the Filter?

Your betta is constantly by the filter for one of two reasons. The first reason is that your betta is hiding. Bettas hide when they are bullied by other fish or if they are sick. The next reason is that your tank’s water is poor, causing your betta to have problems breathing. The water right around the filter is of the best quality.

If you want more tips and guides on aquarium filters, please visit our collection of articles here.

About the author

Hi, I am Rena.
I grew up in a house surrounded by fish tanks.
I have spent my life caring for and writing about fish.
I have studied journalism and worked for online and print magazines.

You can find the articles I wrote here

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