If you're asking how long after you catch a fish and release it before it bites again, I'd say anywhere from a few minutes to the next day. It all depends on the type of fish, competition for food in the water, etc. In small ponds with high numbers of fish competing for food we've caught the same fish again within a 1/2 hour of releasing it.
If you are talking about taking all the fish out of a small pond (fishing it out) that really depends on how many you are taking, the type of fish, how many are in the pond, and their capability to reproduce. If it's a pond about an acre or two and you're just taking a few fish out each trip/week, and they have the ability to reproduce (a quick way to roughly judge this is if there are fish of different sizes there), then I wouldn't worry about fishing it out at all. I have seen small ponds quickly fished out where multiple groups of guys take home limits each day though, but that doesn't sound like what you're describing.
Hope this post was helpful - if you have any questions don't hesitate to ask.
