Hi, The density of any live rock, no matter where it came from, should be such that when it is immersed in your tank, it displaces as little as possible, biologicaly this is the best. Unless it is bleach cleaned and left to dry for use as an ornament, it will allway's have things that are iether dead or waiting for rebirth.[egg's - spawn etc ] Therefor phosphate will be released and it needs to be aborbed . I used highly porouse coral rock that had been bleached & dried, I put it into RO water several times until my TDS reading went from 600 down to 3 - 5tds. Then I put it in the tank and automatically seeded it. It took a while befor life started, but now 6mth later it is lovely rock, and my phosphates are purely related to the amount i feed the fish, Phosphate is held deep within most rock, unless you take it out prior to putting it in the tank, then it is a lenthy buseness to absorb it, even if you do use Rowa-phos etc. Regards.