Thanks for the props on the knowledge
My background includes network (primary) and electronics engineering, and practically running a datacenter with massive electrical requirements, gensets, specialty grounding, well you know
And yeah I had the same nervousness from GFCI, but the safety was too important to me -- so I installed 4 circuits, downstream from UPS backup, with all the equipment and pumps spread among each circuit - so the tank could sustain itself for at least a couple days with some circuits tripping, so long as not all of them go out... current project is to add to that an automated e-mail & text when all power goes out to the tank (via breaker, or downstream gfci)... all this is at least as much fun for me than the actual reef keeping
Now to the problem at hand, there is undoubtedly something up with the skimmer -- but I'm going on a trip in a week so I don't want to change anything in the tank while I'm not around to monitor... but due to the same thing, I will not have pH monitored while I'm away (not the end of the world).
I will do some testing though with it -- I'm thinking a separate bucket of water with the skimmer doing it's thing and the pH probe - to at least eliminate the interaction between the skimmer and something else or the pH probe and something else... full test, another separate circuit, etc.
Now, another question for you (or anyone) related to testing electrical... Will a conductivity test offer any insight here? pH uses reference voltages, right?, and if there is some resistance to ground between different devices, things could be strange... Possibly I'm thinking that the ground from the skimmer is somehow exposed (but if just ground exposed, not a real issue), but perhaps with a higher resistance -- just brainstorming as I'm typing
Cheers!