It all depends on your maintnance routine, filtration, and size of fish. I have 6 green chromis in my 55, along with lots of others. I do have lots of live rock, a large skimmer, and a refugium with cheato algea. So if you are set up correctly, you will be ok....

If you don't skim, do routine water changes, or have small filtration devices, I would not over due it on the number of fish.