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Lots of aquarists may have seen that their fish are hanging around the filter in an aquarium. It may happen for various reasons. However, new aquarists think that it happens just because of its illness. Actually, this is not a correct concept all the time.
Fish are opportunistic feeders so they try to find foods (algae, microorganisms) around filters. Moreover, a stressed or pregnant fish can hide behind a filter due to the lack of hiding spots in the aquarium. Besides this, for having high current fish love to hang around the filter for more oxygen.
This couple of lines may give you a brief idea about the topic. However, you are required to know more about it.
Here I’ll show you some reasons about the nature of aquarium fish which I’ve analysed by observing my aquarium fish. So let’s dive deep into the topic
Why are fish hanging around the filter in an aquarium?
Fish may hang around the filter in the aquarium. Generally, it is not a suspicious thing. However, you have to analyse the tank condition before interpreting a conclusion. Here I’m going to discuss the top seven reasons why your fish are hanging around the filter of your aquarium. Some of my fish also hang around the filter. I’ll discuss it too.
Fish want to find more foods
Fishes are opportunistic feeders. It always hangs around the aquarium to find some extra food. It mainly tries to find some microorganisms or algae to eat. This is the very common nature of fish. Now some algae may stick to the skin of the filter of your aquarium. Fish may come to eat those algae. Fish may come here to eat microorganisms also.
Fishes that are weaker than others may come here to find food. It is because when you provide food it may not be enough for them to reduce their appetite. Maybe they are not strong enough to fight with their companions to grab more food while you are giving. Thus they try to find other food sources in a peaceful place. The back of the filter is the most peaceful place in every aquarium. So fishes love to hang around there to find some extra food.
I have faced these several times. In previous times, the back of my aquarium’s filter had lots of algae and some of my fishes came to eat those algae. Thus you should check the condition of your filter’s area before coming to a conclusion.
The aquarium may be dirty enough
Most of the ornamental fishes like to live in clean and clear water. Now due to lack of maintenance, your fish tank may be dirty enough. However, the space near the filter remains always clean due to the high water current/flow. So it is highly possible that your fishes want to find some clean places in the aquarium and this is why they are hanging around the filter of your aquarium.
I’ve not seen it because I always try to maintain my fish tank well. I try to do a total of 20% water change twice per week and I try to prevent algal blooms by reducing the light intensity. So I haven’t experienced it yet. However, it happens with lots of new aquarists.
Stressed, bullied, or pregnant fish may hide behind the filter
If you notice that mainly a specific couple of your fish is hanging around the filter of your aquarium then you should check its companions’ behavior. If you keep aggressive fish species with peaceful fish then there is a high chance that the peaceful fish species will try to find the safest spot in the aquarium.
For instance, the convict cichlid is a very aggressive fish species. Now if you keep some peaceful fish with it unknowingly then that peaceful fish will try to find a way to live. If you observe this type of thing in an aquarium then you should know that specific fish are stressed enough.
It can happen when they are pregnant also. However, the chances of this are very less. Generally, fishes become aggressive in nature during the breeding period. But it may happen for very small fish.
Lack of hiding spots in the aquarium
Fishes in the aquarium require several hiding spots. These hiding spots help new fishes to feel comfortable. It means if you introduce new fish in the aquarium then it requires a little bit of time to be comfortable. At that time it requires hiding spots. Now if your aquarium does not have any hiding spots then you may hang around the filter to find a comfortable zone.
It is related to the previous point also. It means when a fish is getting so much stress or if it is being bullied then it requires hiding spots. Thus, it hides behind the filter at that time.
My first aquarium was a bare bottom tank and I didn’t put any decorative items in it due to lack of money. Lots of fish at that time hid behind the filter of my aquarium. From that situation, I’ve experienced it.
Read more:- Fish is hiding under a rock: 6 possible causes
Due to bright light intensity
Aquarium lights influence fish behavior also. Lots of new aquarists do not know this fact. However, it is true that if you keep a high-intensity light then fishes may not like it.
Generally, ornamental fishes are nocturnal in nature and they become active when the aquarium light is turned off. These dislike high-intensity light because the temperature of water increases and fishes like cold water. So these try to find places where the light intensity is comparatively dimmer.
Thus you must put fluorescent light on if you have a freshwater fish tank. If you have a reef tank or if you are planning to build a reef tank then you must require some extra knowledge of lighting. You may check my article to know the signs of too much light in the reef tank. Here I’ve described all the aspects scientifically.
High water current provide more oxygen to fish
Fishes love to stay at a high current of water. High current or high water flow means more oxygen is penetrating and increases the concentration of DO (Dissolved Oxygen). It is scientifically proven that to increase the concentration of DO, agitation of water is required. An aquarium filter agitates water the most. At that time the concentration of DO of water increases with it.
As stagnant water does not contain more oxygen so fishes may hang around the filter to find more oxygen to breathe. Fishes breathe with the help of gills. When it hangs around at the high current then it grabs more oxygen from that flow and breathes effortlessly. It only happens when you have a very big aquarium. Otherwise, for small or medium-sized aquariums this is not possible to happen.
Fish love peaceful & cold spots
Most of the aquarium fishes like cold water. Now if your aquarium has an average or high temperature then some of the fishes will try to find the cold spots of the aquarium. As the filter provides fresh water in the aquarium, so space near the aquarium remains comparatively cold all the time. So, some of your aquarium fishes like to hang around the filter.
Not only that, but some of your fishes in the aquarium may like a peaceful place to wander. Now if your aquarium is overpopulated then there might be a chance that some of your fishes are trying to find some peaceful places in the aquarium. Behind the filter is the most peaceful place for some type of fish. However, it varies from fish to fish.
I have faced this several times. Once I put tons of guppies in a 20-gallon fish tank unknowingly. Some strong fishes were absolutely fine but some guppies disliked the overpopulation of the tank. So they used to try to hide behind the filter.
Read Here:- Fish jumped out from aquarium: Scientific Truth from a veterinary
Why is my fish swimming in one corner?
Fishes require proper oxygen to be active. If the water of the aquarium does not have the right concentration of DO, then fishes will be inactive. Due to the unstable temperature of aquarium water, fish may stay active for some time. Besides this, if fishes fall asleep then they will stay inactive also.
Here I’ve tried to describe the answer to this question briefly. However, this question may have different types of aspects. If your fish is staying at the bottom and becomes inactive then you don’t need to worry much. It is basic nature, some ornamental fish like catfish. They like to stay at the bottom without any activity.
If your fish is on top of the tank, it means the fish may require more oxygen. To verify this reason you have to observe whether the fish is gasping or not. If it tries to take oxygen from open-air, it means you are required to oxygenate the tank well. However, some aquarium fishes like guppies are top dwellers. So it is basic for them to stay top.
If some of your fishes are not swimming and stay inactive at the same point of the aquarium for a long time, it means those fishes are stressed or they are suffering from a disease. You must take them out from the aquarium and must provide special care to regain their activity.
In this article, I have described why your aquarium fish is hanging around the filter. Some of the reasons I’ve experienced personally and some I’ve gathered for you with the help of thorough research of it.
From years of experience, I can say that your fish may require some extra food to eat and that’s why it is hanging around the filter. There is nothing serious about it. However, it may be stressed for some reasons and that’s why it is doing this kind of behavior. It is possible too but for this conclusion, you have to know about the aggression of its tank mates. Both of these reasons are valid for any type of aquarium but you have to check other reasons too which I’ve described in this article.
So best of luck & happy fishkeeping 🐟