Stray Voltage?

[syncro]

Do I have a problem with stay voltage?

Voltage with nothing plugged in: 5vac
Voltage with Odyssea pump: 35vac
Voltage with Eheim 1000 pump: 15vac

In the past week I've had one clownfish jump out and had trouble with my aquarium controller (solved by the vendor - sounds like configuration data changed in a way that isn't possible by the end user).

It sounds like pumps normally induce 20-30v of voltage because of the rotating magnet. I'm guessing this is ok because very little current will be induced.

I am measuring with a multimeter with one probe in the water and one probe in the third (ground) opening on the outlet. Outlet is GFCI. No ground probe.