I pay 2.50 $ (two) USD per kilo (around 2 pounds) for citric acid at my chemistry supply store, and obviously consider this as cheap.
5% citric acid is supposed to have a pH between 1.80 and 2.00
Dosing example for Citric Acid: 1 Gram of 100% pure citric acid powder per 100 Liter of
nutrient solution = 1% would bring down the PH way under 6 (depending on acidity of the solution).
Hence 0.5-0.75 gr per 100 Liter of nutrient solution is a good starting point to bring down the PH to somewhat under 6. You may simply dissolve 5-7.5 gram in 1 Liter and use 100ml (equals 1/10 of 10 time smore) per 100 Liter. Respectively dissolve 10-15 gram in 2 Liter and use 100ml/100L as well.
PS: I am used to metric weights and volumes, which are actually much easier to calculate, as volume/weight has the same relation (1gr of water = 1 milliliter) hence 10 gr dissolved in 1 Liter equals 1%!
Disclaimer: Use at your own risk
