I have used AZ-NO3,it works but it is too expensive for such a small bottle($30 at 240ml),I have switched to a cheaper alternative,vodka ! Only $18+ for a 1000 ml bottle from duty free shops.
It works,no problem holding NO3 at <1 to 5 with heavy feeding for more than 6 mths,needs a good skimmer though.Cheers.