Should have specified that I grow in soil, as I have no clue about it's use in hydro. :jointsmile:

After a few months of being open, I start to hear the salts conglomerating in the bottoms of the nutes when I shake the bottles, (no build-up in the Grow Big, though) and runoff ph will start to swing. Not wildly, but enough to visually catch your attention.
The monthly mini-flushes at a 1:1 volume of pot per gallons of ph'd water release any salt and nutrient build-up, plus the humic acid is great for the roots. (which coincidentally is to be applied monthly, per instructions)