FISH IN 75GAL

[Delphinus]

I don't think the overall water volume really has any impact, but instead things like how much swimming space there is (and thus, what sort of aquascaping exists), what kind of nutrient export exists (skimming vs. heavy skimming vs. no skimming or whatever), and what existing tankmates there may be.

Bear in mind that except for a handful of species, even small fish can become big fish, with enough time.

FWIW, I have 5 fish in my 75g, and it's probably full or a little bit beyond comfortably-full. Mine are largish fish. They all started small though. Currently the smallest being a 6-line wrasse and the largest being a sailfin tang at about 6" in (3" when I bought him). Others include a lawnmower blenny, a flame hawk, and a female banggai cardinal. About once every 3 or 4 weeks the lawnmower and the tang end up scrapping, and one or both will end up with the equivalent of a black-eye for a day or two. Then they get along fine, until again after 3 weeks one of them says that the other one has a big butt or something and then it starts all over again.

HTH