Conflicting nitrate results

[VB313]

I been battling high nitrate issue since May I discovered my RODI water ive been buying from a LFS for top off and water changes was basically tap water since they haven’t changed filters or media in over a year with 40ppm (API) testing straight from their tap I have since been buying from another LFS and bought a Red Sea test kit hoping for better accuracy but the Red Sea test always reads dark purple darker the The color card

when the API tests 0 Not sure if I’m doing something wrong with the Red Sea test I’ve watched YouTube videos and it appears im doing everything right not really sure what test to go on is Red Sea correct or API?

 

[glb]

I’d recommend investing in a home rodi unit if it’s in your budget. You’ll save yourself a lot of hassle over the long run. All you need is a TDS meter and a chlorine test to make sure your water is pure. As far as tests, Red Sea is much more accurate than API.