Test your tank for cal alk wait 24 hours test again
This will tell you your tanks demands
Use this chart to find out hOw much product. Is required to keep the levels optimal then decide how often you want your doser to run (cycles) find out your dosers pump rating
http://reef.diesyst.com/chemcalc/chemcalc.html
Mine for example runs for 29 sec every 2 hours