I was thinking about getting some corals/mushrooms, when my tank gets healthier. How many fish can be kept with them? Is there a rule of thumb. I notice, most of the tanks have a few fish and a lot of corals. Is there a reason for that? I understand lighting, temps, calcium and other factors are involved, and are different for FOWLR tanks. Can someone lead me in the right direction to understanding this? Thanks in advance!!