I've always read that if the worms have the right conditions they will stay put. That includes the bedding, moisture and food. I think a few will always wander.

Be sure to put some type of metal screening over soil on the bottom or the Moles will have a feast. jim

Have you seen the comments in the other recent thread on European Night Crawlers. Some of the comments were a bit negative

Here is a link that might be useful: European Night Crawlers