It varies whether u wana do fowlr or a reef tank. Its generally ,1 to 2lbs per gallon. U can mix lr and base rock which turns into lr after a few months. I have 40lbs of LR and 20 of base in my 75gal. I add a price of Lr now and then to bulk upSince its my first SW tank, I want to start with fowlr. Which LR should I use?