I dont have an answer to your problem but this also happened to me. I got the prizm a few years ago cuz ppl said it was good. I never got it to work right. With mine it either collected alot of water and had bubbles going into the tank or no foam being collected at all. So i went back to my air pump driven protein skimmer which works great, made by lee's
For a while after i used the prizm as a glorified water pump, not anymore.
It was loud too, i always had a towel over it to help cut down on the noise.
Im gonna see if the lfs will give me store credit for the stupid thing.
Adam