Well, I am keeping my PH in the resv. at 6.0. I am filtering my tap water through a britta filter. My tap is 7.0 PH and after being filtered through the britta filter it nocks it down to ~6.5. After I fill my resv. I put in my grow or bloom, then use PH down to get it to PH 6.0. But I've been using PH 6.0 for everything.