Hi. Sorry to go back to the beginning but from reading your original couple of posts it sounds like you thought that all of you filter cartridges were carbon, and you said that you changed all of your carbon filters every month......... If I am reading that right then you have been changing all of your filter media out every month. This will be the reason that your filters have not cycled fully. It's not an error on your part. The filter manufacturers all say to change filter media about once a month. If they have carbon in them then the carbon filter does need changing once a month or so to keep it working properly, otherwise it stops being effective. Sponge filter media however does not need changing out unless it is physically falling apart. If your filters only have one type that has floss with carbon attached then I would personally recommend you change out for a different sponge or floss only, otherwise every time you change the filter pads out your tank will be going through a new cycle, and by the time the bacteria has started to build up you will be changing the pads again.