Someone just asked me this question – They have built a CFT wheelie bin with my how-to video:
They have worms in the starter material – 12 to 16 inches thick of new bedding. And they are obviously seeing worms come out the bottom into the harvest area.
Here is my answer:
Worms will often be found in the top 12 to 16 inches of material in any deeper system. Them being “surface feeders” is a relative term. Compare that to the anecic and endogeic earthworms which like to be in 4 to 6 feet of soil.
Youll find they drop out the bottom until you get 12 inches (or more) of finished vc under the feeding zone up top.
While there is still food in the highly oxygenated bottom zone of a cft, they will happily live there.
My advice is to keep a tray with some damp bedding under the cft harvest area – tip it back in the top every few days to a week and replace it.
It should happen less as time goes on.
If you have european nightcrawlers in the mix, they are known to like to go deeper than other composting worms, too.
Thanks for reading !