Wanted to post an update here -- the die-off has mostly subsided, but this is expected as the population dwindles wink. That said, apparently enough survived and successfully acclimated that we've had very successful spawning - lots of fathead fry in the pond.

Still see a mature fish fatality every now and again, but haven't really seen the adult minnows around. Hoping the new generation is healthy and better adapted and we'll be in good shape come next spring.

I'll chalk up our issues stress and not properly tempering/acclimating them. I'm sure the supplier isn't top-tier either but at least some of the population was healthy and robust enough to survive the ordeal.

Thanks again for everyone's input.