Man that is so cool. I really appreciate this, as it really looks like a great way to maximize an aio. I have had a lot of trouble with this tank even though I love it lol. I think you've helped me solve my filtration dilemma. Do you have a problem with surface scum? I find it really hard to keep the water levels in the front and back different enough so that the display water "falls" into the back chamber skimming it. My levels are usually the same. I used a clip on surface skimmer from in tank, but my snails kept moving it, throwing off my ato.
I did but I found aiming the return nozzle up gets rid of it. I also aim my power head towards the top. I keep one on the side and the other towards the lower back of the tank. I will move the lower powerhead every once in awhile to ensure all areas get movement. Also with the canister filter, the return nozzle is very strong and keeps everything moving in the second chamber. I'll attach a terrible illustration of my chamber set up and power head placements
1: intake for the canister
2: return for the canister
3:heater
4:ato
The middle chamber I keep broken pieces of live rock