Need help thanks

when there is a layer of oil film in the water surface, the normal way is to attach a surface sceemer to an external filter.
is there any other way to replace the external filter?
or are there any other method to recommend??

[Royston]

I have a 1 ft tank which I use an internal filer to create "waves" to break the surface of the water that also slove the oil firm problem. My the other 2 feet tank I keep molly & platies which seem to "eat" the oil too but not as efficient as the internal filter.