>- all the microbes disappear from a test jug of pond water when it is zapped?
Yes, this is absolutely true for multiple frequency zappers.
A single frequency does not kill all microbes but does kill many. I posted pictures and information about the jar of water test quite some time back and issued a challenge to get zapper makers and users to do the same to compare the results.
I can not say that it is successful every time, it will take the work of others to verify.