Crawfish will kill any fish they can get their claws on. Which includes pretty much everything.
When I was young, I caught a crawdad when I went camping one. It was just a little baby one, about the size of a fingernail.
I managed to keep it alive through the camping trip, and when I took it home, I dumped it in our fish tank, I believe it was around 40-55 gallons.
It somehow thrived off the tropical flakes we gave the fish, and it even made a cave out of the substrate.
Well, eventually it got older, grew pretty big, and it ate all our fish. We had zebra danios, angelfish, bleeding heart tetras, and a common pleco.
Plecos are armored, of course, so the fact it could manage to even harm that is threatening on its own. And zebra danios are fast and speedy, so having fast moving fish doesn't help all too much.
I'd say you keep them alone, honestly.