YAAAAASSSSSSSS! Glad to finally see this beast, what an incredible specimen man!
He maybe my favorite fish but I am not risking injury over it lol. He was on his own for years but recently he has been living with four synodontis cats. I guess its true that they are immune to him.
No joke one that size would pack some serious voltage and would hurt quite a lot or knock you out completely. Even at 12" their discharge is enough if it decided to hit you with full power where it will make your whole arm numb for a few minutes. Don't ask me how I know...
I'd heard Syno's were immune and took the chance with mine many years ago and had the same results. My 5 Syno's that shared a tank with my E-Cat hung out with it and neither bothered the other at all. The one time I introduced another fish that tried to hangout near the E-Cat it was fried the same night.
How are synodontis cats immune?
I've read it has something to do with a fat layer insulating them, which is preventing the discharge from penetrating their skin which is why they don't shock themselves. The discharge follows the path of least resistance and shocks that, so as long as the fish in the discharge are more resistant than something in the surroundings they won't take the majority of the hit is what I took from the article. This was in E-Cats specifically but maybe the Syno's being catfish also have a similar fat layer?
The other theory would be since they can determine when and how much discharge they want to output that they view Syno's as "same team" and don't deliberately shock them whereas the other fish put in the tank they specifically target and the closer proximity to the E-Cat the harder the shock with the worst being actually touching the catfish. This is sheer speculation and open to discussion/interpretation