So I've noticed a fair amount of my sand bed turning to rock. Especially around the base rock - it is as if my base rocks are growing. I pulled out some chunks and broke up some others that weren't too tough, but the stuff that is attached to the base rock is just too hard. My dosing of ESV B-Ionic 2 part had been periodically increased until I observed that Ca and Alk stayed at stable levels, around: Alk: 9.8dkh (Hanna) Ca: 410-420ppm (Red Sea Pro) pH: 7.85 - 7.95 By dosing both 65ml/night, from 8:00PM to 11:00AM, alternating 1 hour apart. So Ca at 8:00PM, Alk at 9:00PM, etc. So last night I left the dosers turned off entirely. Today's measurements: Alk: 8.74dkh Ca: 410ppm pH: 7.83 - 7.87 Alk dropped a lot, pH a little, Ca stayed the same. So I guess I'll go longer with the dosers off and see how much Ca moves. Then try to do the math on how much should really be dosed. This may take a while to get right!