Thanks for your comments, guys.
The reason why I asked at the time was because I couldn't help but get tons of microbubbles after restarting my skimmer (on its lowest possible setting), and I was worried that if the microbubbles killed my other fish that continuing to skim would kill my nemos and cardinal as well (I had already turned off the ozonizer when I discovered the dead fish). After two days of no skimming, I had to clean the water somehow (and keep in mind that I just did a 20% water change as directed after completing the chemi-clean treatment).
Anyway, I believe that the cause was the ozone (as many of those microbubbles were probably ozone-bubbles) and not the chemi-clean, since all fish were very active and healthy up to the point where I restarted my skimming and ozone treatment.
Fortunately, my nemo's and cardinal are still around -- and I have had no other non-fish fatalities that I'm aware of. The skimmer has since stopped producing microbubbles. I have not yet turned the ozonizer back on.
Thanks again,
David
