Originally Posted by SpaceNeedle
Well SAP that is all true, BUT unless you are in the habit of discarding the nutes left in your reservoir (instead of topping it off), and then starting fresh with water and your formula of nutrients, how do you know how much nutes is left in the bin? I don't mean how many gallons you have, but the proportion of nutes to water, because often times, especially in the beginning of flowering, say, they may have well extracted much more water than nutes, so all you should be doing is adding water to make it the same strength is was originally. Perhaps near the end of their cycle, they might be taking on more nutrients than water and what you have left is a very very weak solution. How do you do that without a meter?
SN