Because it is a fairly small and shallow pond it might be more effective to use two smaller surface aerators or fountain type aerators if an aesthetic display is desired. Surface aerators, which create more of a frothy boil of water on the surface, will oxygenate the pond fairly well. A display type of aerating fountain will move less water.
A 1/2 HP decorative fountain that uses 5 Amps will pump about 250 gallons per minute.
A 1/2 HP surface aerator that uses 5 Amps will pump about 880 gallons per minute.
If you compare the gallons moved the surface aerator will be more efficient and use less power as the motor is not required to throw the water high in the air.
Another strategy would be to use bottom mounted diffusers in the pond and an air pump on shore that pushes air into the diffusers which releases micro-bubbles that will circulate water. Often these units can be effective and use even less electricity that surface aerators.
Installation, surroundings and budget can make one technique more desirable over another.
To see some very efficient surface aerators see our recommended system here: http://www.thepondreport.com/store/powerhouse-surface-aerators
When using bottom mounted diffusers the deeper the pond the more effective they will be. A max 7 foot depth is not very deep so the dual surface aerators might be the best choice.