@Psilocubensis, that depends on what run off PH and PH in of the last feeding was. There's no hard and fast rule that I use other than noting the last pH in after adding sulphuric acid and then again after the citric acid, and then from the run off pH I can get an idea of how much citric acid the plant used and how much I should add next time to maintain the average root zone pH I want. If you want to use it in your grow as pH regulation alone it will cause you problems with root zone pH always going too high, but in soil this may actually work really well if you do need to regulate the pH there
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