Yep it was cavitation.

Wayne Sallee
Wayne's Pets



nacree wrote on 12/2/2006 11:01 AM:
As I have read in other posts, 90 degree turns before the pump can
cause cavitation (microbubbles). I took it out yesterday and have a
straight pipe leading to the pump. No bubbles now at all. Just an
update if anyone else has this problem.