[Pockets]

My SunSun Canister filter came with a surface skimmer that does a great job at removing all the surface scum!

 

[Paaron]

Thanks for this info! I have a Fluval Spec for a while and only notice this gunk on the top of this tank- mystery solved!

 

[DaveFish]

I don't know how true this is, but it seems if you add more media to your filter and increase flow through the filter by keeping it clean it can disappear. Maybe it is just anecdotal, but when I keep my filter clean and end up adding a ton of media to the filter it seems to disappear. Also, switching to a lower protein fish food may help. I notice some food produces it more quickly than others.