I've got an Emporer 400 on my 75 gallon tank with cichlids. It's done fine so far for about 1 year. However I was trying to find a way to extend the life of the purchased filter cartridges and improve the water quality at the same time if possible. I was wondering if anyone has found that putting either activated carbon or other filtration media in the secondary filtration cartridges that come with the unit either extended the life of the primary carbon containing cartridges or improved the water quality.