I just got a used Remora Pro and a new Mag3 pump. I had bubbles flowing back into the tank for maybe 3 days. The skimmer is pulling lots of dark brown gunk from the tank. I will say that this particular Remora Pro is noisy. I can hear it in the room next door. The noise appears to be coming from where the water from the pump is being injected into the skimmer. It sounds a lot like the noise you get when you spray a garden hose into a bucket. I've never heard anyone else complain about it so maybe it is peculure to my skimmer. Also I've never seen another Remora Pro in operation so I have no comparison. Hope this helps.