Algae on inside of skimmer...is that normal?

[Michael]

Hi.
I was wondering if it is normal for algae to be on the inside of a Klaes Junior skimmer, or any skimmer for that matter.
I recently had an algae outbreak in my tank, but that is now under control. I noticed that my skimmer has algae (looks like hair algae) on the inside of it.
Using 10k NO flourescent lights on for 10 hours a day.

I haven't heard of a skimmer requiring cleaning. Do they require cleaning once in a while :?:

Thanks

Michael