I take a few frozen green peas out of the freezer and put them in some water, so they'll thoroughly thaw out, before I feed them. I squeeze the peas between my fingers to kind of flatten them out and break the outer covering.

All four of my goldfish eat the peas, and the peas have helped alleviate the buoyancy problems with my fantails

Give them the 'squashed pea' treatment
The next time peas are on the menu for your family, save a few cooked peas for your goldfish. All you need to do is squash each pea slightly and remove the outer skin - the skin is too hard for your fish to digest - and then add one or two peas to your fish tank.

Scientists aren't sure exactly why, but a squashed cooked pea can often help a goldfish that is suffering with swim-bladder disease. The swim-bladder helps a goldfish maintain balance and lets it rise and sink. Swim-bladder disease is often caused by the fish's stomach - which lies next to the swim-bladder - becoming distended and pressing against the swim-bladder.

The squashed pea remedy appears to help by moving food and trapped air out of the fish's stomach, which releases pressure on the swim-bladder.