Originally posted by NORWAY
come on....somebody has to have some scientific answer to this question?
I think the reason why everyone has a diffrent opinion is that everyone has a diffrent experience.
Factors:
Nutrient Import (feeding, dieoffs)
Nutrient Export (denitrification, refugiums, water changes)
Nutrient Transport (burrowing cleaners, strong sand-level currents)
Nutrient Capacity (volume of sand holding nutrients while they are in the process of denitrification.)
The goal is to not let so much crud build up on the sand that it looks bad, and not have so much build up in the sand that it causes a "crash" later. If you have good Nutrient Transport and Export, then you really shouldn't have to disturb the cycle. If you have too much Nutrient Import, or not enough Transport, junk will exceed your capacity and some mishap may disturb it and dump all those nutrients into the water. The deeper the sand bed, the longer it takes to see problems with this balance. If the factors are out of balance, it may be wise to stir the sand occasionally, although if you havn't been doing this regularly since the tank was set up, use a ton of caution and ease into it so you don't release all your stored nutrients into the water at once.
Is that scientific enough for you?