I can really only recommend what I've used. I would either order or build a media box for your first chamber. Personally, I prefer an acrylic box because the solid side walls force the water to run through your media rather than letting it go around. I would also recommend blocking off the lower intake for your rear column so all the water flows through your media. If you're going to run floss, run it in the first level of the box to capture as much detritus as possible before it gets into the rest of the rear. Then I'd use chemi-pure elite in the second level and live rock rubble in the bottom. The second chamber would be good for your heater and more live rock if you wanted to. I just like having the rock contained so its easier to remove if I feel the need to. The third section I would try to get some type of ATO to fit. You could do a refugium in the second chamber if you wanted to. It probably won't do much for nutrient control but if you light it opposite your display, it will help keep your ph stable and cultivate pods. That's more personal preference though.