There's nothing delicate or finicky about siphon systems. Depending on the head... the height of the pond above the outflow... they can really move some water.
When used for an overflow, a pump is not needed. A properly designed siphon will start and stop on its own at the right time.
To draw down a pond, the siphoin may need a pump assist to get it started. Any type of water pump will work, even a very small one. I used a small hand bilge pump, and it worked great. For drawdown, it's important that the pipe joints and valves are absolutely air tight. Otherwise, the siphon will slow down and eventually stop flowing.
