protein skimmer help

I have a reef octopus 1000 protein skimmer and I turned it off in order to do a water change and now it's making a lot more microbubbles than before. I've had this since March. I tried tuning it up and down, but the microbubbles are still there. This photo isn't my protein skimmer, it is a...

I had my protein skimmer, (reef octopus hob 1000) and it was working just fine, barely producing any microbubbles, but I turned it off to do a water change just now and now it's producing microbubbles a lot. I even shut off the tube (the one that allows air to come in) completely and it still...