im curently trying fresh lemon juice as ph down , i have better results when leave tap water for 24 ours to declorinate.
my tap water ph :7,4 and need about 0.4 ml of lemon juice to bring it to 6,2 .
also tested 6 hours later and ph went to 6.4-6.5 . after 12 h same ph.
if i dont leave tap water to declorinate ph after 6 hours goes to 6,8-6,9 . after 12 h ph goes to 7.
it works for me but need to be proactive and have some declonitate water.
citric acid also has similar results but is hard to measure the dose.
some people says that will harm soil bacteria but i dont believe it becouse biobizz bio ph down solution main ingridient is citric acid and organic growers only feeding soil bacterias to feed plants.