Film On Top of the Water

Celtic_Wanderer wrote:
This may sound a little weird, but I have begun to notice a film,
almost like you would see if you mixed oil with water, on the top of my
tank. Granted the tank is only month old, but I have just noticed it
with the last week or so. The color is more of a grayish color? Any
ideas? Does charcoal produce that kind of residue?

Thanks

Celtic Wanderer
See my tank at: home.comcast.net/~Celtic_wanderer