PH is the most important thing in growing hydroponically.
A too high or low PH will quickly show up in plants, sometimes being fatal. Even fluctuations in ph will stress plants, it is important to keep it constant. If you have to adjust your water to use, then do so in a seperate container.
the second most important thing is nutes or ppm. plant s don't use all the nutes in the res., just what they need at that time. as the res lowers it can be topped off once with your ph adjusted water, then check the ppm's and raise as needed. when it needs water again clean the tank out along with the pump, reassemble, refill, test and you're good to go.
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