Time has come to buy new alk and calcium tests and I'm trying to decide between trying Salifert or AF...i currently use AF for alk and Red Sea for calcium but have a feeling the Red Sea test is a little off (it ALWAYS reads low ~380 even though my salt mix should be more like 420 and i don't have too many corals in the tank so I'm gonna switch calcium to either Salifert or AF...I've never used Salifert for either though...anyone have preferences between these two brands for calcium and alk?