CO2 & white goo on airstone

I'm injecting the CO2 from my yeast bottle into the bottom of one of 
those small plastic spring water bottles. the airstone is epoxied 
into the bottom and water enters through holes around the perimeter. 
the top is attached to a small power head. Seems to do the job-CO2 
level is high and plants are taling off.
I noticed that some white jelly-like goo grows on the airstone after 
a while. Anyone know what it is. Harmful or harmless?
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1:  Macaw at tiac_net
2:  bob_woolley at fishmailserver_neuro.mssm.edu
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