Your still worried about your 15ppm nitrate level?
Anyway, I find them to be a waste of money, there are many cheaper alternatives to nitrate reactors, and nitrate reactors are normally used in overcrowded systems with nitrates in the hundreds.
Macro algae, and carbon dosing are two things that pop in to my head, much cheaper, and not overkill for 15ppm nitrate.
I once worried about harmless level differences, in the end i overdosed kalk and had a tank crash, lost a few hundred dollars. Really, in all honesty, Don't Worry about the nitrate level you have at the moment.