help me, physics people!

[daniel_t_miles]

So I was at Burgerville the other day and they have a Ye Olde Tyme Juke Box with lighted tubes of liquid around the edges and bubbles of gas floating up through the liquid. Now, as I understand the world around me, those bubbles of gas should be under less and less pressure the higher they rise in the tube and they should get bigger as they go up. However, in this machine, they got smaller and I can't figure out how this was done. I've posted a video here: http://www.youtube.com/watch?v=CoaoGjIyqwc if you want to see it before suggesting a reason.

This makes no sense!