saltwater aquarium is very hard to take care. you need lot more equipments or tools compare to fresh water aquarium, and all the equipments needed for salt water aqua is very expensive. the lightning, filtration, protein skimmer, salt, live rock, fishes, or coral, all are expensive. you need to have a good filter and lightning, especially when you going to put coral in your tank.
I have 2 clown fish(Nemo), some corals in my 200 lt tank, and this cost me around $4000.
on the other hand you need to maintain the aquarium very often to keep everything on the right track
