carbon

[canadawest]

The bio-theory that you're speaking about Rob is due to the fact that people often use carbon in a canister filter type arrangment. Detritus gets caught in the carbon, then breaks down there potentially causing an increase in nitrates.

I suspect that if you just dropped a carbon bag in your sump or main tank that you would not be contributing to increases in your nitrates at all.

I use carbon for about a week or two each month, or until the carbon bag starts to get clogged in my canister filter (whichever comes first)