If it has been gamma-ray'd it'd be as useless as putting deionised water into your tank. Gamma irradiation is probably the strongest form of destruction this side of the sun. When I was working at Aquasonic, they were the sole distributors of Brightwell Aquatics, however that was 4 or 5 years ago, so things may have changed, tho it's not likely because as far as I know, pretty much every other Brightwell product is bought off them. Going on this tho @
NiCd is right that it could have come in through a backdoor, which means it most likely would have been irradiated, otherwise it would be an illegally sold product if it hasn't.
Having said that tho, ZeoBac is the equivelant product and would work the same way