Hey Joeypaul, so i myself have a clown knife that is over 13inches so trust me when i say they get big! you should start out too see what kinds of food your knife likes, i started mine on sinking shrimp pellets, algae wafers broken up, as well as night-crawlers and the occasional feeder fish. he started at about 6inches and iv had him for a year now, they are awesome fish and are pretty easy to care for. After a while you can feed them more and more just remember they grow quick! mine eats about 6 algea wafers whole in once sitting now and still wants more. Also keep in mind these guys love their own hiding places, so get a big rock or piece of driftwood that he can hide behind for a cave. Hope this helps! Good luck with your new Clown