I have used the following methods to treat Nitrate before
1. DSB, it only took about 2 months to see the initial result, algae free when I had it
2. AZ-NO3, you start to see Nitrate and PO4 reduction in less than 2 weeks. algae free when I had it
3. BRS Pellet+Zeolite, for 4 months, I still have to add extra carbon source to control the no3 and po4. they were kinda out of control, not too bad thou.
4. Ecoback+Zeolite, I like it so far, the glass doesn't get algae cover that quickly, but it might be because I am adding ISO and SP as well.
When I got the NP pellet, I was expecting it works as good as vodka/AZ-NO3, but it's just different. or you should try to double the dosage like Bill did.