There is nothing wrong with what Druluv is proposing..... it's 1980 technology that has a proven track record in being able to maintain many soft corals and some lps corals that have a tolerance to a higher dissolved organic level... but, no sps corals. The nutrient level in the ocean does vary.... being mostly affected by land run-off. The sps regions of the reefs are extremely nutrient poor where even algae has a hard time making a go of it.... our tanks have so many nutrient inputs from our relatively high bio-loads compared to the ocean that even with a high skimming capacity, we still can't reach the low nutrient levels of the open reef....but, we're getting closer, as is evident by our being able to now keep coral species that were out of our reach only a decade ago.
As for my system... I do have a refugium that is bare-bottomed with some liverock and chaetomorpha (for nutrient export harvesting). I vaccum this region frequently as it acts a sort of settlement pond for detritus. It really doesn't supply much food for the tank...the main display probably does more. I run four skimmers and add no additives, as I have a calcium reactor that I'm sure adds all kinds of trace elements from the media. I feed the fish and that's it.
It has always been my contention that we can't replicate a self contained, naturally filtered piece of the ocean... our bio-loads are just too high compared to the ocean, as is shown by every analysis that I've seen of a closed system's water... it's values are, across the board, always greatly higher than those of the open ocean. Those that have gone down this road (which was all of us in 1980), have only been rewared with modest success on certain hardy species....and certainly not with what I'm interested mostly in...sps corals
One last side note, I have several fellow reefer friends in the LA area who are fortunate enough to have access to ocean water to use in their tanks. I find it interesting that their skimmers produce next to nothing after large water changes... and then build to produce more as the days go on.