What do you guys fill your 400's with, I had the blue mech filter going with the carbon taken out of it then filled the media baskets with small matrix in it but noticed the matrix wasnt being used to its full potential, thought about filling the baskets with floss as I think I read before but just went ahead and pulled the baskets and put an additional blue mech filter again no carbon in it gonna see how this does flow is still good but want to know what does everyone else do with thier 400's