Quote Originally Posted by macnasty
excellent answer Herbie. Thanks for taking the time to answer the question so thoroughly; I have a much better understanding of what you mean now. Could I bother you for one more question, maybe 2?

1) if my water is 250 ppm, does this mean I should only change the res once ppm reads 250 again, or somewhere very near? is this a good way for your plants to let you know that it's a good time to change their diapers?

2) if the feeding schedule is designed according to a weekly basis, does this mean, that if a plant in week 4 of flower requiring 1500 ppm drinks, let's say, 2 gallons in a day and the reading the following day is 1(from 1500 the previous day), that it would be okay to feed her just water for the remaining week?

thank you very much, this has been one of the most useful threads i've come across...and judging by the other responses in this thread it looks like welcome information for many others. imo there should really be a sticky explaining this, because the label on the back of nute products is pretty misleading and vague. i think purposefully, so the majority of customers overfeed and therefore over-purchase, but that's a whole other matter...
Answer #1: Good thinking but unfortunately not. Here's why: Every strain and every plant for that matter is unique in its uptake of nutrients. The mix that you are making every week is based on a best floating average or whatever the manufaturer thinks is best for the plants. But in the real world our mileage varies, so that is why it is recommended to replace every 7 to 10 days.

Answer 2: Yes, although based on answer one you can't measure it that way. So do either of these:

1) Feed your plants what they drink in one day with appropriate nute formulation. Tomorrow your rez will be empty or very close too it, and for the rest of the week only keep adding water.

2) Get a large enough reservoir to feed your plants for 7 days, fill with water and add a one day supply of nutes. (Mix and read the PPMs as let's say 1500/7=(whatever that equals) PPM.

Yeah I agree, I don't know if the manufaturers are INTENDING to be vague, but they DEFINATELY are profitting from it. And again, I am not trying to convince anyone to believe me, please call your nute manufacturers.