The essence of a sump is to allow the water to flow over/through extra filter medium. All you really need is a second tank, a return pump and some extra glass.
The tank needs to be separated into chambers in which you can put different filteration, bioballs, filter pads, etc.
The best thing about a sump is that you can hide most of the equipment in there such as heaters, skimmer, etc. so they don't clutter up the main tank.
Design is really down to the individual and what they want to put in it. I have built all my own sumps and each time I forget to allow for some piece of equipment so don't worry if i's not perfect.
As an example my sump has a primary chamber with ceramics and bioballs, a secondary chamber with filter pads, a main chamber with algae & mangroves in a sand bed then a final chamber with the return pump and final filter pads. In the sump I have a Skimmer, UV filter, Light, Heater and Powerheads as well as some shrimps, fish and starfish (don't ask!)
Before filling:
Filters maturing:
(I never said they were pretty!)
HTH
/www.melevsreef.com
