"Mercy killing" hardly described Myrna's flipping the tiny hatchet fish off the deck. "Never felt a thing. I'll put money on it," she said, wiping scales from her hands. "And you'd better not drop any more puny fish in with my boys. Get your own tank, you cheapskate." Bill ran his hands through his thinning gray hair and sighed. It had started with one innocent ten-gallon aquarium, which he had set up to surprise Myrna on her fiftieth birthday in hopes that the hobby might provide some mutual entertainment. But the tank soon multiplied.