most biologists tend to think a pond under 50acres is too small for Crappie. They're just too prolific, especially if there aren't several larger predator species in the same system. Black Crappie are less likely to overpopulate a pond, than are White Crappie, but still require the larger sized pond and heavy predation. Of course, there's always an exception or two. But, on the whole, Crappie are not really a pond fish. They just create too many young.
Theoretic example: Say you had 1 breeding pair of 1lb Crappie, and put them in the pond. And they hooked up. The female has around 10,000 eggs. But, since there's only one male, she only drops half of them. OK you've got 5,000 eggs. Now, consider that 1/10 of that number survive the first year. Now you've got 500 fingerling Crappie. And just for the sake of argument - let's say Mom & Dad eat 1/2 of that brood over the course of the year (or other factors enter). Now you're down to 250 yearlings & a pair of 1.25lb parents. Since it takes about 3yrs for a Crappie to mature ... let's say year #2 goes about the same as year #1. Now you have a pair of 1.5lb grandparent Crappie, 250 two year olds, and 250 yearlings. Then comes year #3 .... and now you potentially have 126 breeding pairs and 250 two year olds. Beyond that ..... you do the math See where this is going ?
(OK, I fudged on my numbers, just to keep it simple - but, you get the point)
By the time there were enough Crappie in the pond, and they had enough to eat to survive & grow, they'd clean out the food source (if there was any) and have to start eating each other. Even that wouldn't stop the numbers growing exponentially, each year, so your pond would eventually overpopulate and the Crappie would be short and thin ... even when they were several years old.
This is just my opinion, though ... based on what I've read and heard. .... cp