Sean, that is my question too? do you run the carbon 24 / 7 and when is it time to change it out? does it strip the water column of vital nutriants or trace elements? (of course we are talking about using brs gfo / gac reactor) does it remove iodine from the water or anything else? I just got one and am putting it online as soon as i get more info.... some say good things about using it and some say bad things, so i'll follow this topic to see what the mixture of answers is...