Clownfishes are not the best swimmers, but they can take on much more powerful wave makers like Vortechs or Tunze, let alone a 350l/hr flow rate... it is obvious that your clown fish died before it got sucked by the pump.
Wave makers and pumps work the same way: there is always an inlet and a outlet. They have to draw water in and push it out. Its just like your electric fan, if you cover the back, there will not be any air pushing out.