Just from a recent experience, the water hose will make them act really strange, but not die. More like skiddish. If you used a water hose, I would suggest never doing that again!

Good luck on the fish. Deffinatly get the grounding thing for stray voltage. That can deffinatly cause fish to die but in my experience. Mine had electrocution marks on them so I dont think that is your issue though.

Jill