If your fish is having trouble swimming or maintaining balance in water, he might have a buoyancy problem. This is one of the most common and frustrating issues confronting fish owners, especially those with goldfish. There are many causes of buoyancy problems. Two factors include the genetically selected rotund body type of fish, and the fact that goldfish, as members of the cyprinid (minnows and carp) family, are physostomous (there is an open connection between the esophagus and the swim bladder). Some investigators believe that floating foods, like pellets or flakes, may make the condition worse or even cause the problem.
Buoyancy problems are typically diagnosed based on a recent history of the goldfish appearing inverted (upside down) at the surface of the water. The condition may be temporary or permanent, and most fish remain alert and continue to eat. The other fish in the aquarium or pond are usually unaffected.
A number of years ago, a hobbyist discovered that feeding affected goldfish a single green pea (canned or cooked and lightly crushed) once daily would cure the problem in some cases. Since that time, several clinical cases improved using this “green pea” treatment. The “green pea” protocol should include increasing the water temperature to 75 to 80 degrees Fahrenheit and continued feeding of the regular commercial fish food, although you should discontinue the feeding of floating pellets or flake food to the affected fish.
Exactly how the “green pea” treatment works is unknown, but it is possible that the pea helps move or displace lighter and/or air-filled food through the digestive tract. And, fortunately for the goldfish owner, the green pea treatment is both harmless and inexpensive.