I’ve been doing AFR for over a year now, and I overdose it according to Tropic Marin’s info. I also do daily 1% AWC and my dKH is around 7.5ish and my calcium between 420 and 440ppm. The water changes make a big difference! My magnesium does run higher, around 1500ppm if the test kits are to be believed. The tank looks great so I think it’s testing.