I really like the bubbles. Will this be an ongoing feature? Thought of something similar for FF but became concerned with the complexity of getting the air to circulate from top to bottom. How do you intend to keep the system from filling up with air? I had thought of an aquarium pump that would recycle the air from top to bottom.
can i make a bit of a suggestion? tell me if i'm wrong, but wouldn't having the intake and outtake on the cylanders right next to eachother mean you'll have still water up toward the top of the tubes that doesn't change temp? if so, you could fix this problem by attaching a long hard tube to the intake hole so that when the water enteres the cylander, it has to exit out at the top and then flow downward, effectivly cooling it just that much more through convection before reaching the outtake hole to be circulated to the rest of hte systems.
I'm thinking it's doing this now:
_| --> \/ cycling water stagnent water
_| <-- \/
EDIT: on a side note, if you did this, you could either have the hard tube extending within the cylander just short enough to be blocked by the white foil, or you could actually make it extend JUST to the edge of the white foil and have the water shoot out in a fountain like fasion (if the pump creates enough pressure) while being lit by the LED's to make a neat sci-fi bubbling test tube effect. just an idea
not sure this would work anyways considering sponges dont create bubbles. maybe if it was already pumping pockets of air it would spread the bubbles out more, but otherwise pushing water through a sponge wouldn't do anything but lower waterflow.