I have a rubbermaid container with two long airstones. The airstones bubble and when the bubbles burst they continuosly soak the medium.<rockwool> Can I shut the pump off at night or will the medium become too dry? Can the plants become overwatered in a hydroponics system? I mean the roots are constantly wet. It seems to me that if your PH is correct and your PPM is not too strong, nothing can go wrong. Am I right or is it more complicated? Any help is much appreciated.

The air pump in a bubbler is meant to run 24/7. The plants will become overwatered if you turn off the pump, as the roots cannot get enough oxygen and your babies can get root-rot. As for the rockwool being constantly in contact with the nutrient solution; you want to lower the nutrient level so that the roots have about an inch or two of air space between the net-cup and the nutrient solution as soon as your roots are long enough. Hope this helps.

L0rdsOth