I
have heard the cheaper roofing EPDM is the same as the pond EPDM, but I
have also heard that it isn't. Anybody know the TRUTH?

Chip

Firestone makes most, if not all EPDM. Some roofing films have a fire
retardant,
but couldn't not find anything else. MSDS does not list a fungicide
content.
I hear it's all the same, save the FR. But....
Contact Firestone and ask.