Plecostomus are really cool. They tenaciously eat algae. I know from experience that one big pleco will keep a six foot tank crystal clean. You should keep them in a tank with bright lighting to encourage algae growth, but you should also have some shade for them to hide in. Either that, or feed them pellets. Plecostomus are very expensive because they are almost impossible to breed in captivity.
The three above photos are a 'common' pleco. The next three are of sailfin gibbiceps pleco's.
