My Rio actually "electrocuted" a ton of my livestock. One morning on the way to work I notice a snail that's upside down trying to right himself, sticking out of his shell pretty far.....OK, I think, he'll eventually right himself and off to work I go.
Come home from work 10 hours later and lights off, go about my business getting to bed. Wake up the next morning and after lights on, I realize all of my turbo snails (mexican and astrea) as well as nassasarius are all upside down and sticking out. Reach the hand in the tank to pick one up and get quite the shock when my arm touches the light fixture and grounds me out.....Literally it shocked the "sheit" out of me.
At this point I don't know what has started to cook my tank but had to unplug everything to find the rio was sending electricity through the tank. It was a smaller powerhead (600 maybe) for circulation.
I lost a starfish, all my hermits, 1 camel shrimp, all my snails, all my pods, my porcelain crabs and who knows what else. As for corals I lost my montis mainly but others suffered as well.
Needless to say in 80# of live rock, I only was able to remove some of the dead. You can only imagine the cycle this put my tank into, and even after water changes galore an unbelievable hair algae epidemic started....then the cyano. The whole ordeal lasted about 4-5 months, ending w/ me completely washing all of my rocks and redoing the aquascape entirely. In the end I like the look better, but those few months were hell!!
A ground probe probably would have helped out here, but still the RIO caused the crash....luckily no oil was released. As for RIO returns, my first gave out on me at night and I was w/o a return for a few days (LFS prices were outrageous for the Mags)....
As for the SEIOs, I've read enough positive things to use one. The majority of negatives have been they are hard to restart. Mine is good so far.
Sorry for the long post, but that's what happened to my tank and put it at least a year behind in growth because of this. HTH someone out there to switch out to maxis or seios or something else. As for the UL listed, I know nothing of that, but the SEIO has a ground plug....