I have 60 pounds in my 40 gallon tank, and to be honest, wish I had added more, I'm focused on inverts, so I have 1 ocellaris (1 didn't make it :( and 1 six line wrasse (I plan on keeping tridacnids, so it's parasite control). The live rock I bought was in 30 pound quantities, so I bought 2 boxes, thought 90 pounds was a bit much, and now that it's cured, I don't think I'll add more, that's 1.5 pounds for my tank per gallon, I can live with that.