re:CO2 & white goo on airstone

>I noticed that some white jelly-like goo grows on the airstone after 
>a while. Anyone know what it is. Harmful or harmless?

This is normal.  It's probably a bacteria that feeds on residuals from the
fermentation process.  If you have two airstones and switch from one to the
other, the "fuzz" goes away after a few days on the unused airstone.  Fish fry
like to nibble on it too.

David W. Webb in brrrr-chilly Plano, Texas (cold for me.  :-))