Skimmer for biocube 29?

Hi, I have a biocube 29. I got the biocube oceanic skimmer. It worked great the first week, and now it stopped making enough bubbles! The bubbles aren't even close to the rim. Ive had it for 3 weeks now. Do you know what the problem could be?

If I cant fix the biocube skimmer, do you guys have any suggestions for one that works well?