Injury in Aquarium Fish – Everything You Need To Know

Injury in Aquarium Fish - Everything You Need To Know

Physical injury is not new among pets. The new aquarists may think that fish escape from physical injuries as they are inside a closed ecosystem which is the tank. However, on the contrary, fish often get physical injuries and hurt themselves and their different body parts during their life in the aquarium. While most of the time, these injuries go unnoticed as they are very small and didn’t require any special attention, serious injuries need immediate action to avoid further complications.

Fish often get lighter injuries when there is an aggressive fish in the tank that likes to attack and mess with the other tank mates. Such light injuries can heal on their own. However, when you notice that fish is under stress, not looking well, eating less, and gasping for air on the tank’s surface, it’s time to take immediate action and check out for the injuries. When serious injuries are not dealt with on time, they welcome different kinds of infections and eventually turn into wounds.

Different causes of injuries in aquarium fish

Although fish live in a closed ecosystem, they are not completely safe. Apart from aggressive fish, there could be many reasons that could lead to injuries among them. However, here are a few major reasons that may lead to injuries among fish.

Fish Fight– When you have a stock with a variety of fish, there are chances that some would be shy and some violent in nature. Aggressive fish like Tiger Barb, Red Tail Shark, Flowerhorn Cichlid, Bucktooth Tetra, Afer Knife, and a few more that show aggressive behavior love fighting with other fish for no reason. On the other hand, some shy fish like Koi Angelfish, Marble Angelfish, Gold Pearscale, Sunset Blushing Veil Angelfish prefer living in peace. Most of the time, the shy fish get injuries when the aggressive ones start dodging them for no reason.

Sharp edges of décor items– We all love to have different types of décor pieces inside the tank to make it look more attractive. Colorful stones, driftwoods, synthetic corals, figurines are some common décor items that people have in their tank. Although these products are sold in a nice condition where there are no sharp edges, with time, they may develop a few and cause harm to the fish. Therefore, you need to keep an eye on the décor items of the tank and check them from time to time to see if they have soft or sharp edges.

Handling– When you are a new aquarist and replacing the water or making routine checks of the tank, you may need to transfer your fish from one tank to another. Chasing the fish around the tank can cause them to rub against rocks and sides of the tank, leading the physical injuries. Even when you use a net while chasing them, the scales get detached, and fin membranes tear.


Unsuccessful predation– Generally, we think that tank mates do not eat each other, but you should not forget that fish are opportunistic. There is an old aquarium saying that “if a fish can fit into another fish’s mouth, chances are it will end up there.” Even the more peaceful fish may eat up the smaller fish of the tank if there is a lack of food. The small fish try to escape, and thus, when such predation remains unsuccessful, the smaller one ends up getting injuries after the fight.

Collisions– Fish are great swimmers indeed, but they often collide with the walls of the tank, décor items, rocks, stones, etc. Although such collisions are not deadly, they may cause some abnormality or deformity in different parts of the body. Some collisions are so hard that they may affect the internal organs of the body too. Bumps on the head or swelling around the mouth are often seen among the aquarium fish that generally occur due to collisions.

Abrasions– Abrasions often occur by the use of the wrong substrate. If you have burrowing aquarium fish like spiny eels and rays and those that prefer dwelling at the bottom, you need to have a substrate that will not harm them. Sharp sand and coarse gravel will affect the bottom dwellers negatively. Injuries due to abrasions often lead to secondary infections.

How to avoid aquarium fish injury

The first thing an aquarium owner can do is to identify the cause of injury to avoid it. So let’s check out how we can handle and avoid the different causes of injury.

  • Do not keep too many aggressive fish in the tank– Being notorious in nature, aggressive fish love fighting with their tank mates and irritate them for no reason. So, try to minimize their number so that all can live peacefully.
  • Check the décor items– Keep an eye on your aquarium’s décor items, especially for the presence of any sharp edge. Feel the edges by touching them, and assure that all are smooth and will not cause any physical injury when the fish rub through them.
  • Handle the fish properly– Use the right net while you handle the fish. For smaller fish, go for a fine net so that their fins and scales do not damage. If you are transferring the fish, use a container rather than the net for maximum safety.
  • Control fin nipping– Often, fish start fin nipping due to various reasons like aggressive behavior, feeding time, etc. At times, the fish just like to explore and start nipping the fins. But the good part is the nibbed fins grow back. You just have to make sure that nipped fins are not wounded or infected.
  • Put the fish in the right size of the tank– The major reason behind fish collision is the use of small size tanks. Fish often collide when there is little space for them to swim. So, pick the right size of the tank. Additionally, try not to expose fish to anything that likely to make them jump. For instance, if you turn the lights of the room before turning the lights of the aquarium, the fish get baffled and start to jump and get injuries by colliding.
  • Use the right substrate– Often overlooked, substrate choice can affect the fish significantly. For instance, catfish and loaches lose their barbels when kept in aquariums with sharp sand or coarse gravel. However, when the fish are kept in tanks with a safer substrate, the barbles grow back.

Treating the physical injury 

The first thing you can do when you notice any of your fish is injured is isolating it in a quarantine tank. In the quarantine tank, the fish will find a de-stressing environment where there will be no fish to injure it further, and the wounds will heal at a much faster rate. You can also provide the required medications in the quarantine tank’s water, like antibiotics that will prevent the wound the get further infected.

It is recommended to keep the pH of the quarantine tank lower, around 6.6, if the fish can withstand it. Low pH is believed to fasten the healing process.

Injury on fins and scales 

Generally, when the scales and fins of the fish are damaged, they heal on their own and did not require any special treatment. However, if you are witnessing patches of blood or visible muscle, or there are symptoms of fin rot, you can provide anti-fin rot, antibacterial or anti-fungal treatment as your fish vet suggests.

Damage on the eye due to injury

There could be superficial damage to the fish, which is seen as slight cloudiness on the fish’s cornea. If you keep the water quality good and every water parameter within the right limit, the eye damage will heal naturally. However, sometimes when eye damage didn’t heal and got worse, it may lead to serious conditions like popeye and sometimes partial loss of vision. Although vision loss does not probe any other health complications, a fish that cannot see properly cannot perform a lot of tasks like feeding and become an easy predation option for the hunter fish.


Physical damage on any part is distressing for the fish. The fish’s body works to repair the damaged part and heal the wound. Whether it is about damaged fins, scales, bumps on the head, swelling on the mouth, or any eye injury, the fish gets into stress. Stress often leads to lowering the immune response that invites different bacterial, viral, and fungal infections.

Therefore, the priority of every fish owner should always be to protect the fish from getting such physical injuries. It will prevent further diseases and infections that may occur due to them. Apart from that, always feed healthy food, so that fish’s body heals up naturally and easily fight off the infections.

And lastly, do not panic if you see any injury on your fish, as most of them are not dangerous. Getting injured is a part of their life, growth, and development.

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5 thoughts on “Injury in Aquarium Fish – Everything You Need To Know

  1. Dishant says:

    Recently my goldfish got badly injured by driftwood when I saw small piece of wood was inside the mouth of my goldfish till it’s right gills really struggling to get it out I saw and gently pulled it out and some of blood came out . I put it in a quarantine tank with bactonil in it . Can anybody tell me how can I save my fish

  2. Donna says:

    My one fish was attached by a raccoon I believe. There is a 1 1/2 wound on each side. How can I help him recover?

  3. khloe says:

    my newborn pea pufferfish injured their fin win i was trying to clean out their tank. they are still alive and breathing but doing nothing but sitting in the same spot all day. any recommendations on what i should do? they don’t want to eat and they are just sitting alone all day not moving at all. is this normal behavior for an injured fish?

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