Here's what a skimmer cup looks like after one year of not cleaning
 

My MR-2 beckett with healthy dose of laziness:

http://i22.photobucket.com/albums/b3...1-02173516.jpg

This isn't a small cup either, it's 5 inches across.

http://i22.photobucket.com/albums/b3...1-02173351.jpg

When I cleaned it, it had a gelatinous consistency and didn't really smell, believe it or not.

I do not recommend doing this. :o

looks like what it is....fish crap!

After cleaning it did you notice any change in your parameters?

I just cleaned it today and I'm not putting it back on, going skimmerless. It's in the for sale forum, actually. It does pull out the baby crap, if someone wants it, although these pics made me think about keeping it...