I have had this same problem. Purigen works without a doubt. Just by one or two 100 ml bags and put one of each invyour filters. They are small so they will fit. The great thing about it is you can recharge the purigen every Couple of months or so. http://www.amazon.com/Seachem-165-P...e=UTF8&qid=1365464493&sr=8-1&keywords=Purigen you will be blown away at the results