I was wanting to grow shrimp and freshwater lobster, too.

When I tried it a few years ago starting with just crawdads, I was immediately overrun by psychotic racoons. The racoons never went after any of my fish setups, but they came like guided missiles to my crawdads. They destroyed anything and everything to get at them, it was not a happy time. When I got rid of the crawdads, the racoons stopped coming.

Here's my theory: racoons are used to smelling fish and not being able to get them (since fish can easily swim away to deeper water in the wild), but since crawdads generally live near the shore, the racoons know they can get them. So when they smell fish, they don't care, but when they smell crawdads, they think "dinnertime!" and go bonkers.

Someday I'll return to trying to grow shrimp/prawns and freshwater lobster, but not until I can secure the setup behind major fencing and steel walls.