While its not its primary purpose Prist does kill microbial growth also along with anti icing. We use prist in our fuel mixed from the port just for this reason.

My recommendation would be to simply get a Mrfunnel from northern tool supply and just use that. if anything is wrong with the fuel you will know. I always use a MR funnel to fill my main fuel jug.
Here is a link. Best 16 dollars you can spend to save your plane.
http://www.northerntool.com/shop/too...8787_200578787