I have mine on for 12 hours a day. I found it impossible to sleep with the noise so I bought a timer for it. The bubbles don't really provide much oxygen anyway, it's got more to do with the bubbles moving the water on the surface and that way getting more oxygen in the water. I have my spray bar directed across the surface so that will move the water enough anyway. Some people don't use airstones at all and their oxygen levels are still ok, it's often really more for show.