Microbubbles...

[fishbait]

For those of you who offered advice a couple days ago on my dying torch (thank you, but its still going downhill), I throw out another question: how deadly are microbubbles? And could they be the cause of my dying corals?

While at the LFS today we were brainstorming and the guy mentioned microbubbles being harmful. Then I realized I had seen lots of these in our tank, in fact the powerheads seem to be frequently collecting and spewing these out. I figured out they are coming up from the return line coming out of the sump, and think I might have found a likely air leak spot as well. That will be tomorrrow's project to fix; however has anyone else had experience with microbubbles killing stuff? Can corals recover after the problem is corrected?