well....... it happens to me everytime i put my hands into my ref where my H&S is sitting, i can see the bubbles going up to the collection cup begin to decline........ (same as when feeding)........ think the logic behind this according to the reefer who sold me this skimmer is that, most of the time, our hands contain an amt of unnoticeable oil (although minimal), is enuf to affect the skimmer's efficiency for a short period...... same goes for feeding.
juz me 2 cents.