I have a 6105 and 6040, bought them brand new last November. Until now they are still making super loud clicking sound when the intensity starts from 0%. Cleaned several times but it didn't help anything. This sound is so loud that it always scares my fish...This sound is also appeared on both external control and 7090 controller, when setting 7090 as pulse with pulsing from 0% to set intensity. If it is from 1% to set intensity there will be no click. Couldn't find any useful info about this, and it makes me thinking of returning the powerhead...Anyone can help would be appreciate!