I'm currently dosing Kalkwasser. I have a 40 Breeder, 5 gallons in the 10 gallon sump and a 5 gallon refugium. I drip Kalkwasser from a ZooMed Little Dripper at about a gallon of weak Kalk solution a day. The Little Dripper holds a little over a half gallon and I add it once in the morning and once in the evening. This has maintained my Alkalinity, stabilized my pH and add Ca.