livwyr25, i know what you mean! My brother has a Penguin 125 on his 70 ltr (gallons conversion anyone?) tank, and only recently has started producing fine bubbles which make the tank look cloudy. They are starting to annoy me (I maintain his tank because i am fed up with mine).
I was wondering whether they are due to salt, because only on the last water change (somewhere at the start of this week) i added aquarium tonic salts, but I don't know whether this affects the bubbles in the water. When the water level runs low in the tank, the filter produces bubbles, but they floated to the surface, and were quite big. But these bubbles now are small and float quite slowly, hardly getting to the surface. Also, if you look from outside below the tank up at the surface of the water, you can see little floating bubbles.
I have read that if you have foam on the surface of the water, it means something is wrong, but not having seen this 'foam', i don't know whether it is or not. I was wondering whether anyone has had this problem, and how they sorted it.