Originally Posted by hagfish
Well, they usually don't work quite right at first. They have to be broken in which takes at least a couple days. But that doesn't mean they won't pull out any waste necessarily. You may want to lower the water level in your riser tube if you think it's filling too fast. But if the stuff in the cup is pretty dry foamy then you may have just had a lot to pull out of the tank.
What kind of skimmer is it?
amiracle hang on wet/dryfilter with built-in protein skimmer. And it was foam coming up the tube,but in the holding cup was green liquid that filled the cup