I'm not really sure what the max is per say for a tank, but I feel as if the water is clean and they are healthy... no harm done.
The funny thing I have learnt in this life of hobby is trust everything people tell you about "your" tank with a gain of salt.. not everything works for everyone across the board.. I went to a nem tank because I was having troubles keeping hard corals.. They would only last a month. I found out nems and zoa's thrive and do awesome in my tanks.
I was told by a person how came over to pick up some nem clones that my water looked too clean and my tanks substrate has no foul or mess.. This really got me thinking of why I was having problems growing some corals. All my levels are perfect, I do weekly water changes, and try to keep the water topped off the best I can until I can get an ATO. I do not douse my tank at all, and my skimmer only runs for 4 hours a day. Who knows why my tank is so clean, but I'm just glad I do not have many issues like others with algae.