5 Reasons Why Your Fish Stay Near The Filter

Why do my fish hang around near the filter?Your fish will give you indicators that something isn’t right in their tank even if everything else seems to be fine.

Why are my fish hanging around the filter? There are several reasons why your fish are spending time together around the filter. It could be in their nature to do so or there could also be an issue with the tank itself.

Analyzation of the situation is needed to help your fish. Look at their behavior and the type of fish that are staying near the filter. To help you out below are questions that need to be answered.

Read further to discover the reason your fish are hanging out near the filter and what you can do to help.

What the filter does and pinpointing the issue

First, we have to look at exactly the filter does in the tank. Its main purpose is to clean out the pollutants from uneaten food, decaying plants, and the various chemicals caused by your fish.

This vacuum also creates a current in the tank mimicking their natural environment. The cleanest and most oxygen-rich water will be near the filter.

There are a variety of reasons why your fish might be spending time near the filter.

To determine the reason we need to ask some questions.

  • Are all of your fish staying near the filter?
  • When was the last time you cleaned the aquarium?
  • If it is only a few are they the same species?
  • What is the gender of the fish that will not move around the tank?
  • What size of the fish is near the filter?
  • What size is your tank and how many fish do you have?

Answer these questions will narrow done the issue. Also look at when this behavior started, if they have always been near the filter or if it is a sudden change.

Just because your fish are staying near the filter doesn’t mean they are sick, but if it is a sudden change then it does mean that there is something wrong either with the tank or their health.

Reasons why and what to do about it

While some issues are obvious, all of your fish near the filter or the top of the tank points to an issue with either the tank, filter or water chemistry.

Smaller numbers of fish point to something behavioral such as territorial behavior or mating. Some issues are interconnected if you have a bully in the mix, they might not be compatible with the other fish or the tank itself is too small.

Some others are less obvious, such as the feeding process for each particular fish.

why are my fish hiding behind the filter?
Corydoras pygmaeus

Below are the top reasons for this behavior and ways that you can fix it, read each one thoroughly to get the main reason instead of what may be just a symptom.

1. They need a breath

The main purpose of the filter is cleaning the toxins from the water it also creates a current in the tank. This is for two reasons, it mimics the fish’s natural environment and the disruption of the water gives the fish oxygen to breath.

When the water flows by their gills it gives them a chance to take a breath.

If all of your fish are handing out near the filter it has something to do with the tank itself, most likely that they are not getting enough oxygen. Your fish are suffocating. Since the current is faster near the filter it will create the opportunity to catch a breath.

There are a few ways to help get more oxygen in the water. First, you want to make sure there is a current flowing throughout your tank.

This can be done by either increasing the speed on the filter itself or if you have low current fish adding a pump to another section of the tank. Or you can add a bubbler to the tank to break up the surface of the water bringing oxygen down into the tank.

Adding plants strategically around the tank will also create oxygen by absorbing the toxins in the tank created by your fish.

If you have a lid to your tank make sure there is some space between it and the surface of the water.

2. It’s a fast meal

Life in the water is a harsh environment for those who inhabit it. A lack of food being one. So your fish are naturally opportunistic when it comes to eating.

The big fish will eat the small fish because in their mind they don’t know when their next meal will come so you might as well eat now. A part of the opportunist attitude is getting food the easiest way possible.

If they can just hang out and have food brought to them they will.

If the filter In your tank is causing a high current smaller fish will be sweep away in the waters allowing larger fish to just hanging out by the filter to snatch them when the smaller one passes by.

It’s like a delivery service for your fish. Make sure your fish are compatible with one another or of a similar size.

Fish have an array of ways to feed. Some eat pellets or smaller fish, scavengers, and filter feeders. If there are only certain species that are hanging near the filter it could be due to how they feed.

Some types of fish are filter feeders, meaning they have a specialized feeding system where they filter out food through the current. Sometimes filter feeders will hang out near the filter since it is the best food source.fish always at the filter

3. How clean is your tank?

Another reason why all of your fish are hanging out near the filter could be because the water near the bottom isn’t clean. Since the filter is drawing in water that section of the tank is the cleanest.

If the bottom is dirty then they are drowning in their waste.

Check the bottom of the tank for any uneaten food or decaying plants. If this toxic matter is abundant first check the filter to make sure it’s working correctly. If your filter is working check the water by conducting tests.

You can buy a simple tester kit at your local pet store.

To prevent this from happening in the future don’t overfeed your fish so that there are little leftovers. Also, purchase compatible scavenger types such as shrimp to eat uneaten food.

Adding plants will absorb the toxins in the water created by your fish and will put out oxygen.

4. There is a bully in the group or it’s breeding time

Some fish can be territorial when it comes to space. Unfortunately, the bigger fish will pick on the smaller ones. If there is an inadequate place to hide they will go where they feel there is more cover. Sometimes that is the filter.

Look at the types of fish that you have and make sure they are compatible with each other. Sometimes introducing larger numbers of the ones that are bullied will create more of a balance in the tank.

Similar to bullied fish if all of your female fish are hanging out near the filter it might just be the best place for them to hide during breeding time.

Smaller fish need a place to hide and feel secure.

Adding plants, caves and decor provide safe places for the smaller fish to run to when the larger are becoming aggressive.

We show you 8 reasons why your fish are fighting and how to stop it in this article!

5. Your tank is overpopulated

Fish can be quite territorial so they need their own space to get completely comfortable in a tank. If you have a small tank or have too many fish for your tank it will cause the above issues from lack of oxygen to an unclean tank to bullying by larger fish.

Check the correct size for the varieties of fish that you own and for the number of fish. With community tanks the larger the better. Larger tanks allow all of your fish to have their own space with those of their kind which most fish enjoy.

Due to the communication barrier, your fish can’t tell you if something is wrong, but they will let you know in subtle ways. Pay attention to their typical behavior so that when they change you can get down to the issues quickly.

Issues can cause harm to them quickly, but familiarity will help prevent most problems. If none of these reasons fit contact your local pet store to get further assistance.

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