The way I have my JBJ NanoCube 24.

#3 - filter floss pad, sponge (aquaclear 300 fits perfectly) then live rock. Those filters are replaced weekly. I let the sponge dry out and rotate on a weekly basis.

#2 - live rock

#1 - 200 watt heater and maxijet 1200 powerhead

If I purchased an in sump protein skimmer, I would put a Tunze nano 9200/ AquaC Nano Urchin in chamber #1.

If I purchased a hang on the back skimmer, I would put it on chamber #3.

If I wanted a refugium of cheato, I would have it on top of live rock in sump #2.

Some people put in carbon like Seachem purigen but my water stays clear with weekly 30% water changes anyways.