White vinegar in water applied with a cloth and then a bit of newspaper to wipe off. The vinegar cuts through fingrprint grease and water marks no probs.
I thought that the air in the bubbles produced exchange too - afterall the surface area of the air overall (bubbles plus surface) is increased and that is what you are doing by rippling the surface of the water in the tank with the filter.
In theory, you should be able to despense with...