i just bought a shark today. may add a stingray, lionfeeeesh, and maybe an eel.
so i you think about it, this will be A LOT cheaper than a reef tank or a FOWLR tank, since you will only need sand in the main and rock in the sump. if you go for a FOWLR your going to need a hell of a lot of rock. if you go for a reef your going to need a light of powerful lighting, lots of reactors, and constant monitoring!