I have been running a deltec mc500 in my RSM 250 for about two months. Last week it stopped foaming. The pump is pumping water, however no foam is being created. The water level does not even reach the cup. I pulled it out today to see if something was blocking up the pump but I couldn't find anything. I put it in a 5 gal bucket and videoed it. See the link below. I have tried it with the air tub completely open and closed. Any ideas???
Deltec mc500 - YouTube
Deltec mc500 - YouTube