Why Do Fish Lose Fins?

When a fish looses a fin, it is never a good sign. Healthy fish, as a rule, do not loose their fins. However, most fish are rather regenerative in this respect; often a lost fin can be regrown, though this depends on the cause of the damage, and the fish itself. Some causes of missing fins can be treated and reversed. However, this is never a symptom to be taken lightly. A missing fin should be a call to action for fishkeepers.

  1. Fin Rot

    • Follow the manufacturer's directions on fish medications.

      Most types of fin damage can become fin rot. Fin rot is when a damaged fin becomes infected with a secondary infection. A secondary infection is when a bacteria or fungus takes advantage of an injury and aggravates the problem. Fin rot typically starts as a milky white or fuzzy white patch on an injured fin. Left untreated it can chew a fin down to the body of the fish. Fish medication from a pet store can be effective, but it is important to keep up on your water changes and feed a variety of foods to encourage healing.

    Fin Nippers

    • Despite their awkward, slow bodies, puffers are notorious fin-nippers.

      A major cause of fin damage and resulting fin rot is fin-nipping. Many fish nip at the fins of other fish. Tiger barbs are notorious for this. This includes the many varieties of tiger barbs, including the green and albino tiger barbs. However, other fish known to nip include pufferfish (saltwater and freshwater), larger tetras, other barbs, and even some juvenile cichlids. Some fish are magnets for this behavior, like freshwater angelfish, gouramis, and long-finned guppies.

    Fish Fights

    • Cichlids, like these convict cichlids, can be aggressive towards thier own kind and other fish.

      Fish-on-fish violence is another cause of missing fins and fin rot. More malicious than fin-nipping, certain species are known for being violent towards other fish, particularly their own kind. This happens often with Bettas, cichlids and puffers. Even if the initial damage does not destroy the whole fin, opportunistic fin rot can set in, destroying the rest of the fin. Never combine fish known to be aggressive towards each other, as fin rot can be deadly.

    Mechanical Damage

    • Sharp edges on aquarium decorations can injure fish.

      Other sources of injury can harm fish. These include things like nets, invertebrates in the tank (particularly crabs and crayfish), and sharp aquarium decorations. As with fin-nippers and aggressive fish, these injuries can be a fertile field for bacteria and fungi which can lead to series health problems for the fish. Avoid netting fish if possible, and do not purchase decorations with sharp edges.