Backyard Aquaponics
A place to discuss aquaponics

The most efficient pumps for lifting are centrifugal impeller types for low flow compared to head, for high flow the most efficient are axial turbines: think ship screw in a tube (and how many ships does it take to screw in a tube?). The famous Wood's screw pump that is used to keep New Orleans above water (modulo hurricanes and dry levies) is basically an outboard motor in a pipe. Mythbusters used a similar design for one of their shows.

Googling around I found an interesting article that states that "Put in more finite terms, the combined pumps could drain an Olympic-size swimming pool in less than two seconds."

As a reminder, the amount of energy required to lift anything is at least m*g*h, where m is the mass in kg, g is 9.8 m/s^2 and h is the height (head) in metres. So lifting 1kg 1m requires:
You have: 1kg * (9.8m/s^2) * 1m
You want: J
= 9.8

Doing this once per second requires 10W, and a suitably sized cheap aquarium pump will get pretty close to this. If you are just moving water, with no head, then your best bet is a large, slow moving axial flow pump - think ceiling fan under water. A duct will improve performance somewhat. How you power this is up to you, but I would start with a salvaged smartdrive motor. A direct drive from a classic wind pump would work too.[I][I]