how long is sn good for?

[DreamEnd]

I have had the package for about a year now, opened it a couple of times to do the aquarium test but sealed it back up

 

[Deleted member 65988]

3 years, it'll keep its chemical assay for 3 years but judging by the fact that you've opened it a couple of times, depending how long it was for and whether or not it was exposed to moisture or air, it's hard to say.

 

[Minsu]

I did the same, opened it a couple of times during last 3 months. One guy on this forum told me that there was a chance for transforming to nitrate.. So idk