Problem with ph and dkh

[batt600]

Im having a problem keeping my ph stable and my dkh is dropping know at 7 dkh and ph at 8.0. What can i do to keep a stable ph and dkh ,my cal level is 480 dont have a mag test kit going to get one today. Any thing to does to keep it were it should be ?

 

[Aquatic Life Direct]

My guess is the mag. You probably need to add some in. Usually they all work together so if your dkh and cal are good, its most likely your mag.