what is wrong?

a friend at college has asked me to look up a problem he is having with his cichlids. the fish is breathing very fast and its stomach is swelling what could be wrong with it? the fish has been swimming around with its mouth open.

Note: he has been feeding the fish with water pleas and worms from a pond outside in the garden(which alot of us have been telling him not to do)
Thanks in advance.

Cheers Capps, i looked up Bloat with a friend and that seems to be what his problem is.