The bubble breaking level in the skiimer looks way too low. Start it someone between where the neck connects to the body, but no higher than the bottom of the collection cup. Then let it break in and adjust up about 1/2" daily until you get desired skimming results.
how much is draining out every 3 days... that seems quite often to be draining out the cup? i was just about to recommend that you up the bubble breaking level another 1/2" so more of the crud gets into the cup instead of staying on the neck... but that would produce more liquid as well.
Oh maybe just a 1/2-3/4 of an inch. If I don't drain it and wait till the end of the week on water change day , the cup is about half full. I just drain it just to be on the safe side, just in case of a hiccup ..lol
I would raise it about 1/2" and let it run that way for the next week. I judging based on your photo of the dirty collection cup that the bubble breaking level might still be a little low, so the skimmer not functioning at it's best.
Just look at the yuck! The best par was , telling the wife to come here as I was cleaning the skimmer cup out. I said look and see. Then I got a punch in the arm and a walk off, while she says . That's f-n nasty!!!! Lol
red reefer, yep! I can feed and what isn't caught by the sock, the skimmer gets it..... I am so glad I listen to a fellow reefer and bout this skimmer. note: this is on a 40 breeder with a 20L, sump. Just as a FYI ! I clean it out every other week.