Surface skimmer and internal filter match

[andrew73]

Hi guys,

I've noticed an oily layer at the surface of late. Even with an air stone, it's still there. I was wondering if anyone has suggestions for a filter/skimmer match for a 55l tank? I'm using Eheim 2008 at the moment and I think it's insufficient.

My tank is low tech-only moss, some black neons, red eye tetras, rasboras and a pair of red tailed sharks!

Thanks!!!