also farmer ive never really had ph probs. my res in my recirculating is always 6.0-5.7 around there adding nutes and topping off daily. weekly res change and 2 week flush. i used to extract water from the slabs to check too and it was always right on. my problems been root rot from too much water, i believe anyway and was told. i used to water 4 times a day 20 min on with 2 gal hr drip emitters. i was told to water ONLY when the slabs dry out, so maybe when they dry ill run into ph probs?? ill be on it hopefully. i tried DWC with NO success, but i plan on trying that again someday. paid 400 for the unit!!!