Hi Ben,
First up the water from the main tank overflows into a pre filter chamber in the sump. the pipe goes almost to the bottom of this chamber (25mm short) and the water has to seep upward through bioballs, a juwel course filterpad, a bag of rowaphos and a filter pad before overflowing this chamber and into the sump proper. In the first chamber of the two chamber sump I have my small Nano Skimmer and Cheato Algae. This in turn flows into the second chamber where I keep a few pieces of liverock, a few frags and some astrea snails. The return pump is outside the sump so the water is syphoned from compartment two toward the pump and back up into the aquarium proper. Make sence, if not see pic below.
Note That is an old pic, the skimmer is in the first compartment, but this lets you see the setup better. On top of the blue sponge is a bag of Rowaphos and a filter pad to stop the small Fe fines from entering the sump from the Rowaphos. I change the Rowaphos on a monthly basis, I change the top filter pad weekly. I've rinsed the blue pad twice in the last year.
I perform a waterchange once maybe twice weekly of 12 litres at any one time. This along with not overfeeding and one starvation day each week seems to work for me in keeping Nitrates down.
For the corals I spot feed the Duncans and the Blasto with frozen Krill. Brineshrimp, Mysis and Bloodworm. I hatch Brineshrimp on a daily basis and feed the tank with this (fish and corals) Scooter blenny loves this. Lastly I also give a dose of DT's Live Phyotoplankton twice a week.
Hopes this helps
Regards
BigC