It is a slow process if you are using NoPox with their instructions. It is a slower process if you cut the initial dose by 1/2 to 1/3 which is what you should be doing.
NoPox works and works well. However, you want to go slow and dose based on total water volume not to include rocks, sand, etc. So water volume only. Calculate that, pick best reef tank option (sps, fish only, mixed, etc), look at their recommended starting dose in the instructions, and my suggestion is to dose 1/3 of that after taking your initial nitrate and phosphate readings. Dose in the morning or day, repeat same time daily, dose manually at first, and retest parameters after 3 days to see what is doing. Repeat same dose and testing pattern for at least two to three weeks until you start to see a pattern. Then decide if you want to increase dose by a little bit until you are at the level you want.
If you read various threads here NoPox can reduce your nutrients to zero if you are not careful. So the general consensus is to go slow and reduce the recommended dose. Test twice a week.