Film on water surface

[Lurch]

Over the last few weeks I have noticed a film covering the surface of the water in my tank, my fish are now breathing faster since it got there. Does anyone know what it is and could it be stopping oxygen from entering the water? Also do air pumps and airstones help put oxygen into the water or do the bubbles just pass through?

[Ira]

It's possible if the film is thick enough it might be interfering with aeration. Depends on who you ask about airstones and bubbles. A lot of people say that bubbles themselves make absolutely no difference it's just the disturbance they make at the surface that aerates the water. Personally, I think there must be at least a small amount of oxygen transfer through the surface of the bubble, even if it is significantly less than at the surface.

[Caryl]

I agree with Ira.

If you have a filter, or bubbles, breaking the water surface it will be ok but if you have a calm surface, the oil slick will be interfering with the oxygen.

I seem to remember someone saying they thought it was due to too many nitrates (or ntrites, I always get them mixed up).

Get some paper towel and carefully drape it on the surface. I should suck up the film. Might take several pieces of towel, depending on the size of the tank.

[Deleatidium]

My tank had a film such as you described for a period (at least a few months) but then it disappeared by itself. It didn't seem to harm my fish.

I assume it had something to do with water chemistry.