Plecos are vegetarians. They eat algae out of the tank, of course. They also like raw lettuce, cucumber or zuchini. You can also buy algae wafers at the store, and feed him a couple at night before you go to bed. They eat best at night. The algae wafers are great, because then you can clean the tank without worrying about getting rid of all his food, and you don't have to leave a light on to grow algae all the time. They also need a piece of drift wood in the tank, on the bottom. They rasp on the wood with their "teeth" and ingest bits of wood. This helps them digest their food properly.

Plecos get HUGE, so plan on buying him a larger tank, if he is in a fairly small one now. My friend has one that is almost as long as her 55 gallon tank. She has to put on welding gloves and grab him to take him out of the tank to clean it. Plecos are a very ancient species of fish. They haven't evolved much in eons. They are cool.