Why is My Goldfish Swimming Belly-up?

The antics of fancy goldfish are fun to watch, except when they are always swimming belly-up. Here are the causes, and what you can do to help the fish.

There are a variety of reasons as to why a fancy goldfish may be swimming upside down or on its side. The reasons could be genetic, or the fish could have a bacterial infection. Swim bladder disease is the term used to describe these different problems, as these problems, whether genetic or bacterial, originate with the swim bladder.

The Swim Bladder

Before we move on, a general understanding of the swim bladder is needed. The swim bladder is a balloon-like organ filled with air that serves as a ballast, much like that of a submarine, in a fish. Valves in the swim bladder regulate the intake and outtake of the air so that the fish can remain right side up.

Genetic Reasons for Belly-up Goldfish

Fancy goldfish come in some truly weird and wonderful shapes and sizes, but none of this is natural. All goldfish came from the carp. The different shapes and mutations of fancy goldfish have been developed by thousands of years of selective breeding. You will not find a redcap oranda or a ranchu swimming around in the wild.

The egg-shaped abdomens of fancy goldfish brought about by selective breeding means that their intestines are squeezed into a much smaller space than in the originating species of the carp. As the fish eats, food can get impacted in the gut, which has a smaller space in which to expand, causing blockages. This can have a couple of effects.

One is that gas from the digesting food builds up in the intestines, causing the fish to become bloated. This bloating causes the swim bladder to shift, throwing the fish off balance.

The other is that the impacted food pushes against a valve in the swim bladder, making it difficult to release oxygen, rendering the fish unable to swim right side up.

There are some simple cures for this:

  1. Don’t feed the fish for a couple of days. The impaction may work itself out.
  2. Feed the fish green peas. The fiber in peas often helps to clean out the impaction.
  3. Feed the fish live or frozen foods, like brine shrimp and bloodworms.
  4. Only feed the fish high-quality flake, and soak it first. This will ensure the dry food has already expanded and doesn’t get stuck in the gut.

If none of these methods work, the goldfish could have a bacterial infection.

Bacterial Infections

A fancy goldfish can contract a bacterial infection from the water. This bacteria lines the walls of the swim bladder, and, once again, makes it difficult to regulate air intake. Bacterial infections are often caused by poor water quality. Test your aquarium water, and make sure it falls within the proper parameters for keeping goldfish. If it doesn’t, take proper measures to fix it. A local aquarium store can help.

Read here how to prevent your aquarium fish from getting sick.

Next, the fish will have to be medicated. An antibiotic, such as tetracycline or erythromycin, should be used. It is always best to set up a hospital tank to medicate fish.

If All Else Fails…

The swim bladder of the goldfish could have been malformed at birth, developing in two separate sections. As the fish gets older and the sections get bigger, it gets harder for the swim bladder to regulate each section, and harder for the fish to stay right side up.

Unfortunately, without surgery, there is nothing that can be done. Since most people won’t seek out surgery for a goldfish, the fish will have to live with it. The good news is, that, a goldfish can, in fact, live with this condition for quite some time. Goldy will just have to get used to looking at the world upside down.



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