I have had bio-wheels for a long, long time. I have seen this before, just not to that extent. Your bio-wheels are not yet loaded with nitrifying bacteria yet. They will turn a brown/green color when they do. Another part is that the bubbles are caused from excess proteins. This is what we call surface scum. You can correct the issue by backing off how much food you are putting into the tank (I am assuming you are doing weekly water changes here), and by lowering your water level so that the water returning into the tank will drive the surface scum back into the water column where you filter has a chance to get it (again). I think the problem will work itself out once your bio-wheels "mature".