thanks for that, just want to check that i'm going to do this right. I only mix up the nutrient with the water as i need it, so should i add ph up to my tank of water which sits at ph7 from the tap, so that when i add my nutrient it should be at about 6.5-6.8, as when i add the nutrient that is when it lowers to around the 6 or lower mark. If so what should i make the water ph, about 7.8 or so to allow for the lowering of the nutrient? I will have to get another ph tester with a bigger range, but once i've flushed how long do i wait before adding more nutes, just once it needs a drink again? Hope i don't sound too stupid, thanks