i only go above the net pots when there new clones and the roots are just getting started. just high enough to keep the roots wet. once the root system grows threw i keep it a couple in. below the net pots. JMO
its also important to keep the water temps down 65 F. is good warm water will cause loads of problems
and make sure theres no light at all getting into the bucket the sell lids to put over the net pots they also help stop algae growth