Drawing up some ideas for rock and sand. I think that I will go light on the rock, make 3 or 4 distinct islands. If anyone has ordered from Marco rocks, is the Key Largo rock something that I could get away using 25 lbs in my display? I would also like to get a moderate sand bed, maybe 2 inches, I'm thinking I'll do two 30lb bags...any input is appreciated since I haven't done this in a minute...