In our Farm Fountain we used a Basic Stamp 2 with a solid state relay to turn the pump on and off.

We have it coming on each 12 minutes for 1 minute in a repeating cycle.

You can find a lesson on howto wire and program the project at the New Electronic Artist web site chapter 9.

If you do not want to do electronics you can use a commercial timer from Omron that with some relatively simple AC wiring will allow the same timing cycles. It can be purchased directly from Omron for about $75.

We have not tried the H3CR-F8 AC100-240 Omron timer though we discussed this application with an Omron engineer and purchase these at your own risk.

They require power and they can switch up to 250 volts AC at up to 5 Amps, so make sure that your pump is not more than 5 amps when it is switching on and off.