Good points J/PAardvark,but I must disagree on clams being a key factor in this type of system.
They are nearly autotrophic,with phytoplankton being used as there source of heteretrophy.You want fauna/flora that are known to be dissolved organic uptakers.I dont think Clams fall into this category.Just about any coral is capable of "absorption" feeding,includeing SPS(bad term).Acropora sp. from the Caribbean can be found in lagoons so i don't feel that a skimmer is needed if you want to grow SPStype corals that fit the biotope of this tank.I recall seeing one of Eric B's old 40 breeders that was skimmerless and it had various types of "SPS" corals in it.I do think an agressive carbon filtration scheme would work well for this type of tank as PA suggests.