Just pit a string of electric wire around it.Only thing is he probably will know.

My husband modified a Fishock electric fence by using bamboo poles for the uprights and copper tubing instead of the wire. A wire leads from the transformer and wraps around the copper. It works great and looks nicer than the green plastic poles and wire.

Fishock fences are available at Petco and Petsmart and are lower voltage and safer than livestock fencing which can give quite a jolt.

I've heard from others that a fence won't necessarily do the trick - some birds have been known to fly directly into a pond or sit on the fence and glide in that way. There are very few hard and fast rules for herons. Each bird seems to be different. Our pond is approximately your size and we decided to use a net overnight and when we're not home. I fought it for a long time, but it's really not that bad. The only thing we have to avoid using are very tall plants. It's the only thing that worked on a very persistent heron and gave us peace of mind.

I want to protect kids from falling in my small pond but I don't want to keep small animals away from water's edge, like rabbits and badgers and ducks with babies. If I put a wire fence with metal poles about 10 inches above the ground would that work? Or would other probelms occur that I haven't thought of?

I have a Scarecrow Motion Activated Water Sprinkler (http://www.safepetproducts.com/scarecrow-motion-sprinkler.html0. This keeps away everything when turned on.