There are many reasons why a fish may have a damaged tail or fin. Most of the time, this can be aggression from another fish, damage from aquarium plants or decorations, or an infection.

All this can raise a number of questions such as: will the fins and tail grow back? If so, how fast and whether this process differs in different types of aquarium fish? May I help somehow my fish to grow it back? How to prevent it from happening again?

Let us understand all these nuances.

Will a Fish’s Tail and Fin Heal & Grow Back?

 Most aquarium fish can regrow their tails and fins to some degree but their ability to do so is not magic.  You will need to find out what caused the damage so you can help to prevent it from happening again.  There also has to be optimal conditions in order to encourage it to re-grow.  With hygienic food and clean water, the area will develop new tissue and make new cells on its own.

Causes of Damage to Their Tail and Fins

If your fish has split fins, that is generally a sign of physical damage, which can come from a variety of sources.   Many times it will manifest as a bite-size piece missing or a clean spit.

  • One such cause is aggression from other fish, which is a common reason.  The aggression from other fish can take the form of less fin-nipping from smaller or fish to fighting among other fish.  
  • They can injure their fin on ridged aquarium plants or decorations in the aquarium with sharp edges.
  • They can get injured during transport in aquarium nets
  • Infection can also cause damage.  If the fish has a possible fuzzy ragged edge to it then it is possibly a bacterial infection.  You may also see slimy mucus or red streaking on the fin.  Although the bacteria cannot usually infect a healthy fish, if the fish has injuries from a fight or is stressed from poor conditions in the aquarium, they could get a bacterial infection. This condition is called fin rot, and can often destroy the fin all the way down to the base.
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fish tail

Promoting Re-growth

As soon as you see any damaged fins, you need to take steps to start the healing process.

  • Make sure that the fish is in a tank with clean water.  You will need to perform an additional 25% water changes to remove all the fish wastes from the water in the aquarium
  • Make sure that you are doing the water changes once a week if you see any injuries instead of the normal every two to four weeks water change.
  • Some species will benefit from adding in one tablespoon of aquarium salt for every gallon of water in the aquarium.  Before adding this in, make sure that you look up the species to be sure they can handle this.  Some fish, like the cory catfish, cannot stand even a tiny dose of aquarium salt
  • Sometimes you may need to use antibiotics to help them re-grow their fins but most will re-grow them with any problems.  If they have any disease, like fin rot, their ability to re-grow may be impaired.  When you see infection and the salt does not work or you cannot use salt, talk to the owner of the pet shop about buying some antibiotics.  Make sure that you read the instructions carefully and dose accordingly so you do not kill your fish.
  • Make sure that the other fish in the tank are not harassing them and biting at them
  • You should also check the aquarium decorations to make sure there are no rough edges that they can re-tear their fins on.
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Betta Fish

1. Causes

  • They may be biting their own tail, causing the damage.
  • Sometimes when betta fish are stressed, it will weaken their immune system making them susceptible to fin rot.

2. Prevention

  • You should test the water regularly to make sure that there is no ammonia in it, especially if the injured fish is a betta.
  • Betta fish also need to have a tank that is five gallons or larger with lots of hiding places, a filter, and heater to keep it from getting stressed out as this can cause damage to their tail and fins.
  • You can also add API Stress coat, which is a water conditioner and stress reliever for betta fish that will help reduce the chances of them biting their own tail due to stress.

For a betta fish, it can take a few weeks to a few months for their fin and tail to grow back.  It all depends on the severity of the damage.  It will grow at the same rate as your fingernail.  If they damage it again, it will take longer to heal and re-grow.

fish fin

How to Tell if Their Fins are Growing Back

You can tell if they are growing by closely look at them.  If there is a clear membrane growing at the end, this is the re-growth.  It looks similar to Saran Wrap and is very fragile.  As it re-grows you will see the clear membrane starting to gain color.  The odd thing is that the color may be different from what the original color was.

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  • Fish can re-grow their tail and fin after it heals
  • Damaged fins can be the cause of fighting, illness, or scratching them on aquarium decorations.
  • Most will re-grow on their own with no help but sometimes you will need to use antibiotics
  • When a fish has damage to its tail and/or fin, it can look painful and dramatic but most fish will heal from these as you would heal from a paper cut.  
  • If your fish develops fin rot, you need to treat it as soon as possible because it will progress quickly and a more serious infection can set in and kill the fish.
  • On goldfish, if the tail to completely gone, it will not grow back.
  • To heal, they need lots of healthy water.
  • Their fin and tail are very fragile when they are growing back so you have to make sure that they do not damage it again.
  • You may have to keep them in a separate tank while they are healing to prevent other fish from causing more damage.
  • Do not add aggressive fish to your aquarium
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Hi! I'm Anna and I´m a certified cynologist (KAU, ACW). Expert, blue cross volunteer, owner of Chinese crested kennel "Salvador Dali" and breedless friend called Fenya. "I can't imagine my life without dogs and I totally support the idea #AdoptDontShop".