Goldfish Buoyancy Problems
Fantail goldfish and other varieties of goldfish with rounded bodies (orandas, lionheads, etc.) are more susceptible to swimming and buoyancy abnormalities due to the shape of their body.
Their rounded shape lowers the gas bladder in their abdomen, making them more susceptible to buoyancy disorders. The gas bladder is what normally controls the buoyancy in fish, and in goldfish the gas bladder is connected to the back of the mouth with a small tube, so the fish can add air as needed to maintain normal buoyancy.
Several problems occur in goldfish that can cause abnormal buoyancy problems. The first is that the fish can swallow air when they eat food at the surface. This puts air in their intestines, which has a tendency to flip the fish upside down as the belly becomes more buoyant. These fish will bob at the surface and only be able to swim down with difficulty. Feeding peas (or other high fiber foods) has been shown to help pass the “gas” out of the fish’s intestines and relieve the excess buoyancy.
The second problem also occurs when the goldfish eat food at the surface of the water. Excess air can enter the gas bladder through the pneumatic duct that connects the pharynx to the gas bladder. This will make the fish float to the surface. By feeding sinking pelleted food, flake food that has been soaked so that it sinks or other food that does not float at the surface, the fish are less likely to ingest air or overinflate their gas bladder.
A third possible cause is due to inadequate oxygen in the water. Goldfish are one of the fish species that can survive in low oxygen water by “breathing” air at the water surface/air interface. Goldfish will gulp air at the surface of the water if there isn’t enough oxygen dissolved in the water. This can lead to abnormal air ingestion. Providing good aeration and filtration in an aquarium should reduce this problem.
Goldfish that already have buoyancy disorders can be treated by aquatic veterinarians to remove excess gas from the bladder, usually with supplemental antibiotics to ensure they don’t have bladder infections. The website AquaVetMed.Info can be used to find veterinarians in all parts of the country that practice fish medicine.