sowbugs and potworms are all part of natures group of helpers they work together to help change the organic material into usable compost. If this is bothersome to you , you might do some straining thru some hardware cloth. My bins are already inside in a large closet. I have had pot worms from time to time and sometimes ants and sometimes spider mites although I dont seem to have any of those at the present time. Bins that are too wet will create conditions for some of these critters , adding some dry bedding sometimes helps with that.