2nd grow

5% diluted distilled white vinegar. you won't need much per gallon. I drop a gallon of my tap from about 8.4 to 6.0-6.5 range with roughly 5-6mL. Get a rust-trusty pipette out and slowly figure out a ratio - it'll scale to a reservoir np, if careful with measurements and math. CH₃COOH.. so it won't add anything too funky. CH3COO- and H+ ions. (fairly sure that's the donated proton, lol, wiki will tell us!)