[reefkeeper2]

Yes, there is a ground fault interrupter. I'm assuming it did not trip because the Tunze pump had a two pronged plug and not a grounded three prong.
Polyfilter does not remove metals as completely as Cuprisorb. It is pre-treated so it will not remove trace elements. Cuprisorb will continue to remove metals until the resin is exhausted or the water is stripped. Polyfilter will not work as well for this application.