Hi Dave Is what you are looking at a residue of the treatment you have been using? and if so what does it say on the back of the container, it sounds as though your fish will be fine and I'll hazard a guess that the film will disapear over the next few days.If you are really worried contact the firm I'm sure that they will be happy to lay your fears to rest.The only other thing you can do is have your local HLO give the pond a once over.rgrdsbroxandval