I'm starting new container food gardens using stiff plastic shallow kids pools. They've done well for landscaping albeit low worm propagation when I made shovel slits for drain holes.
This time, I think that I'll drill or melt holes that might be better for worms to travel through, BUT be small enough to keep out moles that eat them. (Ounce of prevention...)
The past few years there's been hardly any moles or voles in the yard. That said, I didn't have a lasagna garden with lots of organic matter between pools. That will doubtless boost the worm population this year and invite moles from my neighbors yard.
I think they will be able to get into the containers IF they can squeeze their heads through.
Q: Any recommendations as to the largest diameter drain holes that I should drill or melt?