Bubbles setting up shop on top

[drobbins27]

I have an undergravel filter which spews out bubbles across the top of the surface in my tank...and through the middle sometimes. Is this a problem? They aren't like foam bubbles, they are just tiny little bubbles which float across the surface until they reach the out-flow stream from my filter. Is this normal? are the pillars where the bubbles are coming from (little boxes filled with some kind of filter media, im guessing carbon) be completely submerged?