Hey y'all, I'm getting to the point in my build where I'm considering aquascaping. I know that I'll be going with aquacultured Florida rock, as opposed to dead or painted rock. My question is, should I go with 60 or 75 lbs? I'm going to try to do two large islands, one slightly bigger than the other. I'm also hoping to have a good amount of open sandbed for zoas and LPS. The dimensions of the tank are 36"x20"x22". Thanks!