No, I would say that is not normal 8O
If it was a proper split in an AC
cord, it would have been a severe shock, not
It sounds like you may have a "ground loop" and the main tank is somehow part of the return. (I experience this in my other hobby, Ham Radio, when I'm powering up transceivers) I would try plugging the Mag 7 into a different outlet (not just another socket on the same extension bus). I would also test it plugged in directly to the wall socket and see if it still gives you a little shock. Plugging into the wall socket means that you will be connected directly to a ground circuit (assuming your house wiring is to code). If the problem occurs when the pump is plugged into an extension strip, it might mean that the "ground return" of the extension strip is faulty.
Keep us updated.
Regards gear-head (W3UTD)