Day 3 running the skimmer. So far appears to be working great Huge decrease in micro bubbles in these three days. When I say micro bubbles I never had a issue with them entering my tank but a small hole close to the collection cup acts as a over flow I would say. On day one it had a solid stream of bubbles how ever they died out very quick. Very pleased with my purchase kinda went out on a limb as I could not find much reviews on the HOB 2000
I have the exact one. if you are getting a gurgling sound from the output it could be the 90 degree elbow in the return chamber. if you remove that it should hel fix that problem. That is what i did as well as take off the sponges since they look bad and they can build u detritus.