he doesn't need one. he got the hippo from me. in the last 2 years, it hasn't grown at all. i had it in my old 90 gallon. same thing for the yellow. it stopped growing a couple years ago. they're the perfect size for a 90 now.astronaut said:also, do you have a tank lined up for the blue tang? because i love them, but im not moving out for another four years... freakin high school... and my parents are NOT going to let me get a 72" long tank.