Concerning you protein skimmer, I also have a SeaClone 100, but I believe many skimmers have similar features, specifically some type of Air Intake... IMO, there's at least two things to consider. First, it usually takes awhile (a few weeks) for a skimmer to get "broken in". Assuming you've been using your skimmer since you started up your tank, that's should not be the problem. Second, the problem I think you're having is that the Air Intake is inproperly adjusted... It may seem like an obvious question, but is yours open? :notsure: I had a problem with that once because I accidently closed it all the way while trying to adjust the bubbles out. Too much air going into your skimmer and on into the tank can be a problem also. If too many bubbles are being pushed through the skimmer, more of the protein you're trying to remove goes
back into the tank , instead of the collection cup. If you'll close the air intake all the way and then slowly turn it, a tiny bit at a time, waiting a
minute or so between turns, you'll slowly get fewer and fewer bubbles. You'll probably end up turning it at least a couple of full turns before it gets close to the proper adjustment level. Remember, you shouldn't remove the air valve totally, nor should it be closed all the way. Patience will pay off with the protein skimmer working as it's intended; removing the "bad" stuff from your water.
Good luck with your tank! HTH