Before trays are put in in use fibers to line the bottom.Bottom and middle tray I use aquatic expert filter floss. I also put my media in those trays. Top tray I use sunjojo filer pad and my chemical media. I use one layer for each tray. The return is I guess technically in the first chamber the picture I
attached was during a deep clean so I moved the return to the middle. No issues w ato or clogging The reason I am having to change frequently is due to my negligence. For the last few months I have been slacking on water changes and with the skimmer+ water pump failure I really started to notice how poorly my tank was doing. It's really helped improve the quality of the tank again with small amounts of spot cleaning and concisnt maintenance.