In a 55 you have limited stocking room! A large trigger produces alot of waste. And everybody who has kept a trigger, regardless of species, know that each trigger has a mind of its own! I've had cables chewed through, arms nipped, and numerous tankmates devoured keeping queens, clowns, and undulates! Humas are a bit, and I mean a BIT , more passive. Most, if not all, puffers get too large for a 55g.