i posted in the general discussion with this question with no helpful answers. i set up 2 fx5s for my 220g. one is just biomax in all 3 trays to house BB only. the second i set up for a mechinacial filter with a pad and carbon in all 3 trays. i used my own socks and filled them with about 40 ounces of carbon. my question is is there such thing as to much carbon that may harm the fish?