Slaters... small bugs with hard shells, flat bodies and fast little legs.. and probably fat on compost have invaded my worm farm which is an old bath tub.

What can I do to get rid of them so that they don't spread all over the farm. We have only had them a short time. They originally came out of some bee hive boxes that were given to us. I'm environmentally conscious, an organic grower so some methods which protect would be appreciated. Any ideas anyone?