OK, I had a few beers and need to chime in.
FastUno - come on over with any test kit you like - nitrates = 0 in my main tank.
By the way - my current tank (and all past) have utilized all 3 methods of denitrification, Berlin, Jalabert and Shimeck (skimmer, plenum and DSB)
My current tank (92 bowfront)has plenum that covers (for all purposes) the whole tank bottom. It is about 2" high. I have 2" of CC on top of that - then I have about 4-5" of pure southdown which was seeded from my original 30g. Worms, pods etc all over the place. My skimmer is an Aqua C Remora Pro hang on back. It creates the nastiest skimmate.
I am heavily stocked and have about 12 fish - 4 of which are tangs which eat like cows (and consequently, sh** like cows). I feed every night and also hang a seaweed selects on every other night. Once a week I soak the mysis in garlic extract. This stuff make skimmate goo!
Ok, that being said, I believe Jackson, skimming is critical, but overskimming may not be best for your tank choice. Jackson, likes a low-nutrient environment so he can keep exotic SPS's (hence the name SPS Pimp)
I plan to keep a very mixed reef. That means I'll need additional nutrients feeding my tank (fuge) as well as a good skimmer to keep nutrients as low as possible or balanced) I do agree with you FU (hehehe Fast Uno abbreviated is FU) about clams as I have noticed that they polish the water nicely but still believe the best way to export nitrates is live rock, fuge, skimmer combo. Again, I keep about 1.75-2.0 lbs of LR per gallon in my tanks.
So, as discussed with Solbby, I plan to have a dsb in my fuge (so I can discard if it gets nasty) and a shalow sand bed in my main tank with tons of critter to keep it happy and sifted. My skimmer is an Aqua C EV 180, and my water volume is about 260g. The reason why I am not going with a 240 is because I only plan to add 2-3 more fish when I convert to the 180 (doubling my water column).
That being said, I agree also with Marrone, it depends on what you want to accomplish, and you should construct your system accordingly.
Consequently, my sump is a 50g ling and is bare bottom so I can siphon out any guck and my frag tank has crushed coral which will be monitored by an engineer goby.
Whew, need another beer.
House