I know everyone says go out and buy ph balance to get you rockwool to the right levels. Well if your on a low budget then use either lime juice of lemon juice. Just one or two drops in the water for each rockwool cube. Wait an hour or two and your rockwool should be at about the right ph. Be careful you dont want to lower your rockwool's ph to far so only use a little and test the water... repeat. comments welcome. im not that experience but i found this worked.