I would agree rock does de-nitrify but certainly not the most efficient like a dsb or plenum system. Or my turf scrubber.
I have seen pics of tanks with very old rock and doing fine. I get the same algae growth on newer expensive Fiji, as my 17yr. old Florida type rock.
How the heck does one take the rock from a full blown reef and cook it. I once also said in regards to rock being changed out after some time, that when I start throwing away rock thats $5 to $10 a pound, that the day I take up another hobby.
