What Fish Floats After Eating?

If an aquarium fish swims funny or floats after eating, the fish probably has issues with his swim bladder. Overeating or constipation can cause the digestive tract to swell and push on the swim bladder -- the organ that control how a fish floats. This can happen in most species of fish occasionally, but a few species and varieties are more prone than others. You can fix this with careful selection of foods.

  1. Goldfish

    • Some varieities of goldfish swim poorly after eating.

      Centuries of selective breeding has turned goldfish from drab carp with the occasional orangish scale to the dazzling fish hobbyists celebrate today. However, selective breeding has produced some varieties of goldfish more likely to get swim bladder issues, especially after overeating. Since goldfish were originally kept in ponds, many varieties -- like the lionhead and others -- were bred to have rounded, egg-shape bodies. This body shape often comes with misshapen swim bladders, which means these fish may have trouble floating right after eating.

    Flowerhorns and Parrot Cichlids

    • Parrot cichlids' exact ancestory is a trade secret.

      Flowerhorns and parrot cichlids are also products of selective breeding. Fish farms in southeast Asia have produced these fish through artificial insemination, crossing various Central American cichlids that would never crossbreed on their own. They often feature unusual bodies, similar to goldfish. Unlike the streamlined wild cichlids they come from, these cichlids have bulbous, rounded bodies. Some types of these cichlids suffer from the same swim bladder issues, particularly after feeding.

    Balloon Mollies

    • Wild mollies originate in Central America.

      Mollies belong to the guppy family. Like guppies, they are easy to breed in captivity, making them ideal for selective breeding. This has produced a wide variety of molly strains, including the balloon molly. Balloon mollies have rounded, short bodies. This, coupled with the fact that mollies are somewhat particular about their water chemistry, makes them likely to suffer from swim bladder issues after eating. You should always keep mollies on the warm side of tropical, 78 to 82 degrees Fahrenheit, and add 1 teaspoon of aquarium salt per gallon to reduce the chance of swim bladder issues.

    Lion Fish

    • Lion fish may swim at odd angles at any time.

      The lion fish is a marine fish who may float funny after eating. However, unlike the other fish here, this is normal for them and not a sign of trouble. Lion fish can manipulate their swim bladders, allowing them to float at funny angles for stalking prey or freaking out their owners. Lion fish can comfortably and safely float upside down, and may do so before, after, during or in the absence of feeding.

    Treating Constipation

    • Many fish will eagerly eat aquarium plants.

      A variety of factors can cause problems with fishes' swim bladders, some of which have no treatment. However, if a fish only floats funny after eating, it is almost certainly constipation. This is one of the few swim bladder issues that's easily treated. You can add 1 to 3 teaspoons of Epsom salt per 5 gallons of aquarium water. You can also change your fish's diet. Vegetarian species like mollies and goldfish foods like live plants. Both species like to munch on Elodea canadensis and Egeria densa, common species in most pet shops. Carnivorous fish can benefit from certain invertebrates like brine shrimp and Daphnia. The chiton in their exoskeletons acts as a laxative.