Join Date: Jul 2009
Location: Colorado Springs
I have duel sunsun 304bs, and they are dead silent. I actually hear the few bubbles in the co2 reactor over them. HOWEVER, They can be noisy at first, or if they are allowed to dry out. My second one I got I almost returned because it was rattling pretty bad. But after a few weeks it became dead silent like the other. I think they need a little bacteria slim to build up to lubricant them.
Every once in a while, or after cleaning something they start humming a bit. Sometimes it can be fixed by turning them off and then back on. But mine always go back to being quiet.