If you don’t stick the lead into anywhere but ground of your outlet, the risk of hurting yourself is minimal. I just had to put it out there as some people might stick it into the outlet itself, which can be bad if you don’t know what you’re doing.
Oh yeah.. just like this is me said, but just tape a longer wire to the red led and into your tank and the black led into the ground of the receptacle. Any movement in readings means you have stray voltage. If it stays at zero then theres nothing.