Kitfox markets the tanks as being Ethanol "Resistant".
This is ethanol resistant, not ethanol proof.
If it was ethanol proof that would mean the fiberglass tanks would take ethanol all day everyday into the future for the life of the tanks with out issue.
This is not the case as ethanol is some corrosive stuff. The fiberglass tanks are treated to be resistant to ethanol. Meaning you can run it and it'll be ok but continued use over a long period of time and the ethanol will eventually start to effect the fiberglass.