Hook up a tesla coil or something from the top.
No, but seriously, hook up the most powerful fans ya want, put a HUGE res on the bottom, and instead of the copper coils, use a huge heater core. Store the pump in the res submerged, and use an old PSU to power the fans. Voila, your own nuclear power plant cooling tower. If a bird shits in it, who cares: just rinse it out every few weeks and you'll be cool.