The best way to control nitrate is to control the source. Overfeeding is generally the number one cause, followed by too many fish. Other sources could be dirty filter pads, inadequate flow causing dietrus to build up, and dirty bioballs or wet dry filter.
A nitrate reducer probably won't be very effective for reducing your nitrate levels, and there are far more efficient ways of reducing nitrates, sounds like you have a pretty good water change schedule, so can you give some details on your setup. What do you have for filtration, are you running a refugium, how many fish, what do you have for a cleanup crew, and are you using a deep sand bed?