poorly fish

Question
hiya, ive had my fancy goldfish about two years now in that time hes lived in a basic plastic tank of tapwater a vase and a biorb tropicl tank,which did have tropical fish in ages ago but they all died. so recently well last week y house mate got some guuppys and tetra's which was fine theyre all getting along i feed them twice a day theyv got living plants etc. but my goldfish has started just floating t the top which he was doing before but then seemed to get more active however now the guppys are picking on him so ive just had to put him back in the little plastic tank with no punp or anything just water. he still just floats and seems to have boyancey issues when he tries to swim he goes upside down and all over the place now hes floating on his side at the top with an eye and a fin out of the water,its been going on a few days and i want to no what i cant do to help him even if it is just old age i feel sorry for the little guy ! if you can help please please do.thankyou!! flossie

Answer
Guppy's and tetra's should not be kept in the same tank as goldfish. They are tropical, needing warm water, and the goldfish is a cold water fish. That being said, it sounds like your goldfish is suffering from swim bladder disease. Feed him cooked shelled peas. Not too many, just 1 or 2. Make sure you do not feed him the outer shell because he cannot digest it. Make sure his water is clean and he needs a filter. Let me know how he is doing.