when to replace your carbon?

[cbjedi]

I have an 80-gallon reef and a 20-gallon sump. Right now I put my phosphate remover in a bag and place it in the canister and leave it until I see a spike in the phosphates. Then I change it out. I do the same with my carbon. Sometime I leave it in there for two months. The Phasban last longer then the carbon, I know. Am I asking for trouble leaving the carbon in there for that long? I was thinking of just dropping both bags into the sump. That way I have easier access to them. As for the phosban, I have a test kit to know when to replace it but what is the rule for carbon? Thanks Erik

 

[Randy Holmes-Farley]

I would remove the carbon after about a month or so.

Other opinions?