No, we're referring to the carbon that was taken out so it didn't remove the meds. Otherwise, you're right TKOS! Unless you have a formula to calculate the uptake of "x" medicine by "x" amount of carbon that is "x" days old and can therefore compensate for said uptake by adding extra meds to the tank. Or, you can assume the carbon is depleted of its capability of absorbing meds (quite possible) and treat it as if it doesn't remove any meds. In which case, why have it in there if it isn't doing what it's designed to do?