Yes, the red positive probe was submerged in tank water and the negative was in the 3rd D shaped hole in the wall, and also tried a power bar ground hole with no difference.
Not sure if this could be related but something strange I noticed was testing the GFCI wall plug I get 120 volts each, but if I test the power bar plugs (2 y/o
Coralife digital power centre) and get 39-40 volts for each plug.
I will try each unit in its own when I have time this afternoon and post results