Is there always suppose to be foam at the top ? Sometimes, mine is just water. And is the cup suppose to be full of liquid ? Mine is just dirty foam, no liquid.
It depends how you are running the skimmer. I run mine pretty dry, meaning more foam and less liquid, others run theirs wet, producing more liquid. Is this a new skimmer, or is it just filling up with clear liquid?
That sound about right to me. My skimmer foam disappears when I feed, put my hand in the water, add buffer, and any other thing I introduce to the tank. It's back to normal in a few minutes.