There is a local restaurant that I frequent that has a large cylindrical FOWLR. I'd estimate the tank to be in the 500 gallon range, so it is big, but its not that big ..... because it contains a stupefying collection of fish. If I tried to keep even a subset of those fish in my 265 it would be WWIII. In no particular order, three large hippos, a 12" sohal, an 8" clown, a few trigger fish, and four large green chromis. Fish don't look great, a lot of HLLE (assume they run copper), but they persist ... so how do they do it?