10% weekly without fail for the past 3 months no difference from the 20% every 15 days, the major difference was when I added chaettomorphia the nitrates and phosphate levels were neutralized. Recently added a better skimmer well it still hasnt broken in...but its in hopes that my past skimmer wasnt right for my setup, my chaetto grew like crazy pointing me to the reasoning that I have dirty water even if my water tests say 0, I see better PE now that I dont do the A and B 2 part and now use the BRS stuff manually, seems my chases are with magnesium, alkalinity and towards the 4th day calcium, definitely want to automate my sytem with a dosing unit, I actually see how much the tank needs as opposed to testing then adding the setup takes in the same almost weekly now for the past 4 weeks. I am fairly new to reefing only 11 months now. I took over another guys established 4 year mostly softy tank with all hob stuff and when it leaked all over my house I changed the tank to a sump setup, okay life story here...sorrry to rant