upside down Ryukin Goldfish

Question
Our goldfish has been hanging out upside down at the bottom of the tank. He will occasionally swim normal and then go back to upside dwon. Our tank is clean and he has only has his long time companion a Koi. Do you know what could be wrong with him?

Answer
Hi Victoria,

Could you describe the problem more in detail? Post a picture, if possible, and ask a follow-up question. There's a link on the question page to post an image, and that would help greatly. This, and the info below, would be extremely helpful for me to diagnose the fish's conditions and to give you a treatment plan much more easily.

Please include the following info:

-The size of the tank (In liters or gallons)
-The filter in the tank, if you have one
-The temperature of the tank
-Feeding routine
-Symptoms on fish's body
-Any other notable things?

Your Goldfish may have Swim Bladder Disease. It can be caused by a variety of things, and will affect the swim bladder, which is a gas-filled organ which controls whether the fish rises or sinks. In the meantime, perform 10% water changes daily, and feed some fresh or defrosted peas to the Goldfish. Peas are known to cure goldfish of Swim Bladder disease.

Good Luck, and I hope your fish recovers!