I don't run a calc reactor..but I do run a phos reactor..I use the phos-ban reactor, with either phos-ban, or seachem's version...I use 250ml and run it off it's own pump from my sump..I want the granules to perculate like coffee grinds in an urn..I usually replace when my tests begin to show an increase in PO again..they are very very easy to set up...good luck with yours..