I find with my skimmer it will bubble over that after a water change, I leave it off for a couple of hours it's usually fine after that although mine is nothing like yours (octopus 150) could the water outlet be restricted in some way? Keep in mind I'm not at all familiar with those skimmers, air inlet could be blocked too but you have a lot of bubbles so it wouldn't be that, I see you raised the whole skimmer right up so I don't think it's that either, I tend to think it could be the water outlet, when I first set up my fist tank it came with a terrible skimmer, from the factory all of those skimmers came with the water outlets being restricted (I found out the hard way) it was a piece of tube being pushed into the elbows too far and causing it to be partially blocked,
http://youtu.be/3H2Jy7rgjl4 that link is exactly what I had and will also explain what I'm talking about, I hope that helps you out, good luck