Here is what you need to know about sumps:
http://www.melevsreef.com/what_sump.html

A protein skimmer removes DOCs (dissolved organic compounds) from the water before they can break down.

You should use a gravel vac to siphon the detritus out of the crushed coral every couple of months. I had that substrate in my 29g, and it pulled out some foul stuff every time. I just siphoned what I could reach, and occasionally I would get very aggressive and move LR and corals to siphon out more areas of substrate normally not accessible.

A timer is key. They aren't expensive, and lock in a light schedule.

You can also run fresh carbon in a canister filter or Phosban Reactor to remove organics from the water, helping clarify the water significantly.

Try to feed only enough, but not too much. If you see food in the tank 5 mins after you dosed the tank, it is too much food. I feed heavily, but have the equipment to compensate for that habit.