I think they get around a foot or slightly larger... and will eat anything that can fit in their absurdly large mouth... I wouldn't put this fish with anything any more then an inch smaller then it and that's pushing it... If you put a really small guy, say 4-6" w/ the CK it would probably work I would want to start the pleco a little larger then that though... or you could start the Gulper smaller but then the CK might pick on it... as for max tank size say it does get 12-14" a 75-90 would probably be min. IMO Just do a search on planetcatfish.com it's pretty simple and informative.