it's a protein layer, made by waste, fixed by having surface turbulence...
create some surface agitation, not only to keep from seeing it, but it
breaks it down, moves it, helps to keep it from building up...
"Aku, Shapeshifting Master Of Darkness" wrote in message
...
Took out my carbon inserts and used peat instead. now there's a nasty "oil
slick" at the top of the tank. anyway to get rid of it w/o putting the
carbon back in?