Quick skimmer Q

[jim27]

Here's a pick: http://www.***************.com/images/berlin.gif See the top where it says carbo air filter, I need to know what goes in that because right now theres nothing in mine. I also want to know how often I'm supposed to clean the collection cup(right now it is half full of gree/brown water and foam).
EDIT-I keep reading that skimmers arn't supposed to make any bubbles in the tank but mine does. It doesn't make a lot, you can only see them when you get close to the tank. Will the bubbles eventually go away(the skimmers only been running for two days)?

 

[mr . salty]

I've never seen any skimmer have anything up there.I would just leave it empty.The cup should be cleaned out at least every week...For the bubbles,you could try putting a foam filter over the return.This will act as a bubble trap...