Matt hit it on the head with his predator vs prey assessment.

If I was starting a pond it would be stocked with only largemouth & bluegill (or other similar sunfish species). I've read about recommended stocking ratios (including what the age of the fish should be and a schedule for initial stocking) and recommended selective harvest plans to maintain a healthy balance in a pond.

In some parts of the country people like to also have catfish in the pond but as Matt said that is introducing another predator that needs to be accounted for.