Discrepancy between Red Sea and Hanna Checker

[PghReef]

Being overly paranoid I always try to test parameters with 2 different tests to compare results. I've noticed for quite awhile the Red Sea alkalinity test reads about a point lower than red sea. Red sea is slowly only 8.1 dkh where the checker reads 9.1. As a 3rd test I have Api which you cant read decimals but it does read somewhere between 8 and 9.

Just wondering if anyone else has ever noticed this? I know their Mag reads higher on average but never read anything about alk reading lower

 

[NeonRabbit221B]

IME I have found that the hanna checker is highly susceptible to screwed readings with the vials are not properly cleaned (inside and out) and depending if the control is checked with the same light. I think it would be better to pick a test a stick with it. Stability is far more important than being unknowingly off by .5 dkh.

EDIT: But no, you are not crazy. I get slightly lower readings on red sea/api.