Dry Rock Suppliers

[Reefer Rob]

I suspect the anoxic zone begins much closer to the surface. IMO the bacteria living in the top layer of the rock would use up the oxygen very quickly. I've always had 0 nitrates with my porous, thin, loosely spaced rock, and I like tons of flow.

I'm not sure if any studies have been done on the distance oxygen penetrate live rock, but it would be interesting to find out. Where did you get 1 to 4 inches from?

[FitoPharmer]

Well first off you need a very fine sandbed at least 3-4 inches deep to start getting Anaerobic zones. I have seen live rock so porous it almost puts crushed coral to shame.

To say "Heavy, dense rock, whether it's live or dry is useless, and will just lead to frustration with your nutrient levels." is much more of a stretch. Depending on who reads that advice it could be taken the wrong way, when using really dense rock like tonga branch is fine.