A few months in on my 140g build, I started seeing high nitrates (50-60ppm). I was hoping that my caulurpa refugeum would keep it under control, but it obviously wasn't. I started doing 40 gallon (~25% of total volume) water changes every other week... that kept it from rising further, but really didn't reduce it much. I picked up a good gravel vac a month or so, continued with the same 40 gallon every other week changes, but used the gravel vac instead of just siphoning water. Nitrates are falling in a controlled fashion now, I'm down to about 20ppm (measured just _before_ I do the water change).
I'm a big fan of stability... I'd always rather adjust slowly, rather than shock things with a major change.
Oh, I picked up the Nyos nitrate test kit that
BRS recommends... and I concur. Works great, gives me repeatable readings, anyway. Accurate? Who knows, I don't have anything to compare it to... Reads quite a bit higher than my old test kit, anyway... which is likely why I let it get out of control before I noticed it in the first place.
I'm going to be adding some sand detrivores... nassarius snails, maybe a fighting conch... I already have a small goatfish, but he's not getting very deep into the (1.5") sand bed. I'm hoping that some additional sand dwellers will reduce the need for the gravel vac.