the hippo tangs in my LFS are about less that 2", now i own a 57 US gallon i think!?! (48 UK gallon, I KNOW!!) and i once considered buying one, i didnt hold back because of the size, i held back because the ick!! i thought there would be loads of room for him to swim, i know my tank would have been temporary accomodation, but if it meant him a decent "upbringing" i would of thought that would of been ok, a tang that size in a 8 ft tank would look almighy puny....especially if you stocked it with other larger fish, adult size though,i totally understand the need. in london zoo they have a MASSIVE one, it really made me think "now thats why you guys FOREVER go on about the sheer size of this beast!!" it was lovely thou! and you could see every single detail in his colour etc, it was amazing. i now think it is one of the beautifulest fish available, and that comes with a high price and a disese risk! good luck.