Bob, I'll try to find some material, but before the sandbed craze, that's all that was used. The anaerobic areas in the rock house the bacteria required for denitrification. My first reef tank (bare bottom) had no nitrates.
A sand bed may/will allow greater stocking capacity, but the rock will remove nitrates. This was the technology in the mid 90's.
Most reading material I have is printed, ie, older FAMA mags. I'll see what I can dig up electronically.
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Brad
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