I have a friend who has a 90g reef that I've watched go steadily downhill as a result of overstocking. Great Lakes's advice is pretty good, his/her recommendation will keep you out of trouble. If it was a FO or FOWLR tank, and you really had massive filtration, I mean like one of those 60" floor model skimmers from Lifereef, you could go as much as 1" of fish for every 5 gallons. Note I said *could* 1"/5g is doable, but not without problems. I've had a 10g FOWLR cycling since march 8th. I plan on housing a manderin dragonet in it later on this year, and hopefully one of the 2" flasher wrasses. I am quite dubious though as to rather or not the parameters will be possible to keep under control.