Thanks for the heads up.
I have been using these type of cannisters since last year and have not seen any problems. The tank is full of breeding cherry shrimp and amano shrimp as well as several fish and they show no signs of distress. Perhaps there is oil in there, but based on my experience it's not a problem. Perhaps the oil is only dispersed at greater velocity ie. 100 psi shots out of a bb gun? Not sure, but I can't say I've ever had a problem.
If folks are concerned though there are beverage grade cylinders available which the manufacturer says is 99.97% pure Co2.
http://www.austinhomebrew.com/produc...ducts_id=10142