Not lightening but I had an accident with power feeding my well pump grounding to the casing of the well... and of course it apparently hit my Miss Piggy, a 35" Chagoi. She doesn't
have a curved spine, but the swimming erratically when startled sounds very familiar.
I consulted a vet here locally who is experienced with koi and he said it's not unusual for the largest one to take the majority of the voltage compared to the others (I also had 6 other
fish in the pond that were completely unaffected). His only advise was to watch and she might get better... she might not. Nothing I could really do either way. She resides in the
800 gallon Intex pool in my garage.
I'm curious if your Sanke swims anything like she does?