I had a ton of problems with the Aquarium Systems' Visi-Jet protein skimmer. It would either make so much noise I could not sleep at night, or it would do nothing at all and never create the foam that a P/S should make. On a good day when it did work, it filled my tank with microbubbles and rendered it cloudy. I did a ton of research and found that a large number of experts advised against the use of Aquarium Systems protein skimmers.
I wanted to keep the cost of a new skimmer within reason and ended up purchasing a Berlin Air-Lift 90 for just over $40 (with air pump). It thus far has worked GREAT. It is quiet, effective and even though what it collects makes me want to gag, I am glad it is in the retainer cup and NOT in my tank. Just my thoughts