Thanks Bill,
I sent TJ a PM. I'm thinking 500 northern crays for brood stock. You know my little puddle. Does that sound like a reasonable number?
I got a message back from TJ with some sage advice:
" I don't think you need the headache of the potential downside of the Northern's burrowing habit. I don't know how deep the burrows go, but I've got thousands of them."
Maybe I need to keep looking for a medium size non-burrowing species.