There's a joint near my house where, at certain times of the year, you can buy bulk fish to stock a pond. I had a one-acre. spring-fed, 20-foot-deep pond on the lot next door. There was big largemouth bass, bluegill, sunfish, apparently some catfish. So I bought a bunch of channel cats, trout and perch and dumped them in there. I think the bass that were in there ate the perch as they entered the water because I never saw a single one of them again.
Yep, baitfish go in first so they have a little time to grow.