I have a 35 gallon tank with a dual under gravel filter system. In this tank I have been keeping fancy gold fish, shubunkins, orandas, ryukins. etc The problem tarted with an oranda, the fish could not stay up right, I was told to feed the fish peas and that it had a balast problem. This worked for a while but the fish eventually died. Boo. Then a similar problem happened to the subunkin, he can't stay up right or even stay up... when he stops moving he sinks to the bottom of the tank. What in the world is causing this? Neither one of these fish were very old oranda about 3 years and the shubunkin about 9 years.