Skimmer not skimming?

[SuperXdude]

I was reading back posts from the last four months or so, and made an observation that someone else had made.

Although my tank is just over a week old, I noticed my skimmer is not pulling the gunk out like it did the first couple of days.

First 5-6 days, I emptied a half cup or more of goo out. (2-3 inch level)

Recently, it's been 1/4 to 1/2 inch for a 24 hour period.

Is the water that clean? Is it doing that good a job skimming?

Thanks!

SuperX