if it is an in-sump skimmer then the water is to high, if it is a hang on skimmer than the body is either setting to low, or the inlet pump is up to high. you can usually control it with the flow valves that come with skimmers to tune it in from those points.
Do you mean that you skimmer has been set the same way forever and it just now started producing extra wet nog? If so, it could be due to anything that has been added to your tank. Too many proteins added via food, dead fish, chemicals, etc. can all cause the skimmer to go nuts and a lot of times completely overflow.
But if you just want your nog thicker... like Jolson said, adjust your skimmer. Each skimmer adjusts slightly different.
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