Very nice pond size! My arizona pond is around 15000 gallons, I used two dragon pumps on it.
Do a search for a pump that might be able to handle that much flow. I choose dragons pumps due to the low electrical use and they turned over the pond nicely.
http://www.wlimstore.com/pumps/dragon.php but not cheap!
From the net:
If you have lots of fish then it's better to have a big pump! You'll want to move the total amount of water through the pump within one hours time. This means that a 2.000 gallon pond will need a 2.000 gallon-per-hour pump. Ponds without fish can do quite nicely with a much smaller pump (or even none at all).
Different pumps have different electricity requirements. Make sure to check the manufacturer's specifications and then do the math before you buy the pump. You could end up with an inexpensive pump, but it will be far more expensive to run.
Total gallons of pond + 3 = Minimum pump size
1" of waterfall/stream surface x 1/2 inch of waterfall/stream depth = 100 gallons per hour
Waterfall/stream width x 100 gallons = Total 1/2 inch gallons per hour
Total 1/2 inch gallons per hour x total 1/2 inches = Total gallons per hour
Watts per hour divided by 1000 = Kilowatts per hour
Kilowatts x 0.10 = Kilowatt dollars per hour )KWDH
KWDH x 24 = Kilowatt dollars per day