I see them in the dollar store, or do the ones from 'The Body Shop' work better LOLYou can try putting a "pod motel" into the 40 for a couple days and see how many move in. What has worked very good for me as a pod motel is what I call a bath scrunchy.....looks like this and cost a couple bucks.
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Maybe putting some flake food in the scrunchy to see if it helps draw in the pods.