I recently bought an emporer 400. I was looking through the library and ran accross this http://www.cichlid-forum.com/articles/power_filter_tricks_v.php. I don't know if I bought the right stuff to put in the cartridges. The only stuff I could find at the local Petsmart is Marineland's Premium Carbon- Ammonia Neutralizing Blend. It is little rocks but I don't know if it will work. What do you think?