I have recently fished in 2 small ponds near my house with crappie in them with intentions of putting crappie in one of my ponds.
In one pond, the fish are good eating size and the bass have been as long as about 1 ft. Fun to catch but no trophy bass that I can tell. However, at one time there were 2 flathead catfish in there and although I have no idea how often this pond is fished or has fish taken out, I think the 2 catfish that used to be there kept the crappie from taking over.
In the other pond, I don't know how often it is fished or had fish taken out either but I filled up my bucket in no time with 6-7" crappie. Fun to catch and I caught 1 good sized bream. But it was obvious to me these crappie really need to be thinned out more often.
Finally, I really believe if you keep just about all the crappie you catch out of a farm pond, unless it is 6" or so, and if you fish it on a regular basis instead of once or twice a year you can have a pond where you and your friends can have a good time catching fish.