As far as I understand this hobbie, we need allot of import / export of nutrients in order to keep a healthy and colorfull reef. Of course nitrates will need to be 0 or low but you will need to add some food for your corals even if you dont have fish.. I have known people that take out their fish thinking that their reef would do better, but actually their reef decayed! Personally I think that one of the most interesting things in an aquarium is the personality of different types of fish. Mine always feed in the same spot, but of course I have a small tank so that is common. Yellow tangs are a must I would say, I have one myself and I would not be able to keep my tank algae free without him!