Here is my sump. On the absolute bottom right is the overflow and emergency overflow. This passes over an array of sock filters and then into the next chamber, where I have two large bio blocks. It passes from there to the rear chamber with the protein skimmer, a pair of reactors (zeo and carbon/GFO) and several heaters. It then goes over a black sponge to the top right return chamber and pump (not easily visible due to the RO reservoir that sits on top).
The idea is that as the water moves around the sump it gets progressively cleaned and treated.