I have had my Oranda goldfish for three years now and he/she/it has been floating at the top of the tank upside down for the past month.
The tank is a 40 gallon with 2 aqua-tech 40 gallon filters. There are 2 other young fancy goldfish in the tank and a bristlenose pleco. They are fed steamed de-shelled peas and sinking pellets regularly, with sinking algae pellets and cucumber for the pleco. For the past two years, there have been no issues with the tank and the water was changed 40% every other week.
When my oranda started floating a month ago, I did a cycle of fasting for 3 days and giving one deshelled pea on the third day for 2 weeks. There was no improvement. When the oranda started developing red sores on the area of the stomach that would poke out of the water, I placed a small plastic mesh divider across a quarter of the tank for him/her/it to rest under to prevent sticking out of the water. I also added a small concentration of aquarium salt to limit stress and help the sores heal.
The sores disappeared but the floating continued. I then tried epsom salt baths to help expel air from the swim bladder. I have been doing these regularly for one week. I see him/her/it expelling bubbles while in the bath. When added back into the tank, he/she/it swims better/near neutrally buoyant for about a minute before swimming to the top and gulping air. Then he/she/it floats upside down at the top of the tank again, until the next bath. There is no pineconing or discoloration of the scales.
None of my other fish exhibit this air gulping behavior or any swim bladder problems. They have been fed and treated regularly throughout all of these treatments. I now do a 10-20% water change every day with the epsom baths and pea feeding /fasting. Nothing is working.
The oranda is still interested in food and will swim down for it, but sometimes he/she/it will not move even if touched. I don't know what else to do and most sites I go to say that it is a bladder deformity and might not ever be fixed. Should I euthanize this fish?