There are skimmer designs available on the Internet, Compuserve and America Online, not to mention in various books. The best designs use a dedicated water pump to feed the skimmer, allow for a large flow rate of water through the skimmer, inject a great deal of air, can be easily and thoroughly dismantled for cleaning, and have a wide neck leading to the foam collection cup. Either continuous or periodic usage of small amounts of activated carbon will assist in the removal of organics and prevent yellowing of the water. I am sure there are those of you out there who question what I have stated. But based on my own experiences and those of thousands of other successful reef aquarists across several continents, the above is all you need in the way of filtration.
Water chemistry is a bit of a bugaboo for many aquarists.
Few understand it well, fewer still seem to want to be bothered with it for whatever reason. The simple fact is that you will need to monitor and understand the water chemistry of the tank if you want to be successful and if you want to be able to trouble-shoot potential problems. Calcifying organisms require both calcium and carbonates in order to form calcium carbonate, the framework of their bodies. Some kits such as those manufactured and sold by LaMotte and Hach measure in ppm of calcium carbonate. It does not really matter which units you use since they can all be converted from one to the other.