Quote Originally Posted by sandman1982
My friend is currently having a similar problem. He is using a drip system with grodan stonewool grow cubes. He will have the pH just right and not 4-5 hours later its back up to over 7.5-8.5. He is getting irritated because he knows this is stunting his plants growth.
Most likely, your friend did not ph his rockwool before using it. that is a common mistake using rockwool...If he did... Then: Does he use tap water?
distilled/ROwater?...Is he using a professional PH up/down product, or home kitchen PH remedy's...i.e. vinegar, lemon juice, pickle juice?

this info is essential to get an informed opinion. lw