Hi, I have this filter, which i have had now for 4 years installed. Nitritech 5000 three vortex. At the moment it is set up with brushes in the first chamber, the second one has a 4 inch thick original course foam circle which sits on that little ledge you see in the chamber, and the last chamber has plastic egg crate grid sitting on the ledge with a couple of media bags full of Alpha rock up to the water line. All the vortex's are clear as the media is held above them. The holes at the bottom have to be set up with outlet pipes and taps to drain off the waist. I do have a pre screen filter.
Im looking to change it slightly by removing the brushes and fitting the foam block from ch2 to ch one and them getting another foam mat or mats to go into 2.
I hope this is of help to you. Anythig more just ask.