yes it is about 400 right now....I will test for mg. That and my alk was down a few days ago to about 2 meq/l and I boosted it......to 4 over a period of 3 days.......ph is 8.3 ....I haven't tested my mg for a while....usually that is pretty stable with water changes....though I have had an increase in my ca consumption and if I have any challenge it is in the ca/alk balances......just like everyone else...