Oily surface water?

[Jweickum]

So as the title suggests my surface water looks really oily. My ammonia is .25

0 nitrites
20 nitrates

Any suggestions?

 

[Mebbid]

It's a biofilm that is developing on the surface of your water. It's common and harmless. If you want it to go away you can either increase surface agitation or buy a surface skimmer