I have 2 Tridents and both act finicky at times. As a matter of fact, my Calcium went out of bound last night after climbing to 600+ but in reality, it was only 420. Anyway, I just care about Alk since I run a CaRx.
My friend’s Trident NP is all the map wrt PO4 ready và so don’t expect much from these hobby-grade devices. At best, you’re looking for trend - which is likely fine, I suppose.