I think I read in a Bassmaster article that they don't like to add crappies to a bass pond. Too much predation on the young bass fry by old papermouth. A mix of bass with lots of bluegills are what I think they recommended. I would keep the cats out if possible. Once when I was a 12 year oldkid a buddy and I caught a bunch of small ones and snuck them into a church pond full of goldfish and fancy fish. We just did it as a joke thinking they were so ugly and when people gathered after mass to look at the pretty fish they would gag when they saw the cats. Long story short the cats killed and ate all the fancy fish within a week. Big investigation but we got away with a stupid kid prank. It has been 45 years and I guess it is safe to admit to it.