Yeh mobay is correct.superthrive just saved a whole crop that was heading for the chop due to very bad ph probs (First go at hydro heehee)mobay said dave man put a quart tablespoon of superthrive in the res stablise the ph and leave them and they perked up in 24 hours now they are looking as if they will be ok . so mobay my good freind thanks again bro once again ur advice was bang on. gratitude mate.be safe all the postman.