I have just started using this diffuser in my tank. It was bought as a back up because I keep breaking the bloody things, and I thought I would try a different type. On the first day the bubbles would come straight out of the hole at the base of the spiral.

After the night time shut off the whole thing backfilled with water up to the NRV, and when the solenoid energised the following day it started working perfectly. It produces some of the finest threads of bubbles I have seen.

Shame it makes a slight squealing noise, though.

Dave.