1-2 pounds per gallon I just set up a 72gall bowfront can see it on the build thread . I used 55 pounds of dry Marco rock and about 120pounds of sand total tank and sump bit the more rock the better, but with small tanks like ours we either sacrifice space for more rock or a little less rock and make it look nice imo. Since I have less rock I am going to be doing 5 gal water change every week to keep things happy!