believe me an octo will seek up on you when you're maintaining the tank. their rings aren't alway shoing and the blend pretty well with their surrounding. they also live in tide pools so it's next to impossible to keep them in a correct environment.
if you want something BA, start with a lion, then get a grouper, then an eel, and THEN you should have attained all the nessicary info needed to keep sharks. a 220 only leaves you with one or two options (and that depends on who you talk to.)