Have you cleaned the inside of the collection cup's tower (the vertical
tube)? I find I need to do this about every three or four days.

If you have, it's possible that some particle has gotten inside the
skimmer and is clogging it. The Remora comes with directions for
removing such a clog, by removing the adjustment screw and running a
brush through the hole. Be very careful when reinserting the
adjustment screw to avoid pushing the screw inside the skimmer.

Susan wrote:
I have a Aqua C Remora that has been running for about 3 months or so. It's
recently slowed down a whole lot and not producing any skim mate hardly at
all. Is this common?