remember that tangs can grow to about 12" in the aquarium
Yes hippos and yellows (among others) do get huge in the wild. However 6" is about what you see in captivity, though they still need at least a 4ft tank long term IMO
. Opinions will vary, but with a 45g IMO
you could get 1 young yellow or hippo if you start with a very young (2") specimen and no other large or aggressive fish, and basically let the tang have the run of the tank. Even then, an upgrade will be needed just year or two away as these fish like lots of swimming room, these guys get to around 6" in captivity. And IMO
they should not be put in a just cycled tank, rather a mature, stable one. A 75g + is ideal for long term. These are coming down in price now too, my lfs
carries 75g with oak stand and hood for $330. Or $99 for the tank.
I actually have a juvenile hippo in my 45g. He is very small, just under 2"; he and a small percula have the run of the tank. Is this ideal? No, but it is IMO
ok for the short term since I have a plan to get at least a 5' tank within the next 18 months or so. The woman who runs one of my lfs
was in the same situation, she at home started with a really small hippo in a 3ft tank and it was several years before he was 3" or so then she moved him to a 55g. So I think there are many factors that go into "can I get a tang?", such as size of system, age and stability of system, number and size (and type) of other fishes, and size and type of tang to be purchased. And finally, wether you plan to upgrade to a larger system as the fish grows.