Planted Tank Enthusiast
Join Date: Aug 2006
Location: Cincinnati, Ohio
I don't use any activated carbon in my tank unless it's a newly setup tank or I'm worried about water quality or something "bad" in there. For example, if I get a used tank I'll run activated carbon for a little bit to make sure there aren't any medicines still lurking in there.
I'm no scientist here, but I'm pretty sure activated carbon removes micronutrients (including Iron!) from planted tanks and should generally be avoided unless nescessary.
As an alternative to activated carbon, you might consider Seachem's Purigen, which is a resin which removes excess organics from the water and polishes quite nicely. It doesn't have any measurable effect on dosed chemicals.