White Film on Water Surface???

[MartyD]

I have a white film on the surface of my 180 gal. reef. The tank has two built-in overflows. I use a large downdraft skimmer. The only additive I use is B-Ionic 2 part calcium buffer. The film remains if I stop using the B-Ionic. I have a shallow sand bed (Southdown). My alkalinity is between 11-12 dKH and pH is in the normal range. Does anyone know what might be causing this and how to correct the problem?

Thanks in advance for your help.

Marty

 

[dad300]

do you have any turbulence on the top of the water? It sounds like organic material is floating to the top and not getting put back into the water column. A powerhead placed so that it creates some ripples in the water may help with the film.