Like Ray, I wouldn't worry too much about 10-15 ppm NO3. It's hard to keep NO3 at zero in a small tank. I always think of nitrate as a measure of tank health, in that only worry if it goes up dramatically.
Mine hovered there for about a year, then suddenly dropped to about 1. I made a few changes at the time, like adding xenia and using kalkwasser instead of B-Ionic, but I really have no idea why the nitrate dropped.
I have never tried the nitrate reductors. There is sporadic discussion of them on web sites, and I have yet to see a post "I love my denitrator!" If you try one, you have to promise to post the results.
I liked Richer's post a lot. It ilustrates the debate nicely, and also that there's more belief than science in the discussion right now. Certain people get it in their heads that they have found enlightenment, and have to try to convince others, even if the data are scanty. It makes for a lot of heat and little light.
As I sit and procrastinate starting an ugly task at work, I wonder about the issue. Seems like the debate about whether DSBs offgas nitrogen vs sequestering nitrate would be relatively easy to answer. Set up tanks, let them run, and measure N2 off the headspace and nitrogen in the sand. Now all I need is the time and money to do the experiment
