Hanna Phos checker: High or Low??

[dreamcatcherr9]

I have never tested my Phosphate before. Figured maybe I should (could). I see Hanna has 2 different Pho’s checkers, high and low.

How do I know which I should get?

What does everyone else use?

Thank you!

 

[PatW]

I use the Phosphorus ULR. It measures in PPB, parts per billion, but you have to convert the results to get ppm in phosphate. It has a lower detectable limit than the Phosphate ULR so it is good for my SPS dominant system.