WORM FARMING - Harvesting your worm casts After a few months or when a layer is full, you should harvest the casts. Remove the top layer and take off the bottom layer. This bottom layer contains the casts. It is ready when few worms can be seen. Remove worm tea from the bottom level. (When using, dilute to the colour of weak tea, usually about 1:10) When one working layer is full, you can add another layer to your worm farm. Place new layer on top of the old one and then add bedding (paper/ straw/ manure) and then add more food scraps. Add food only to the new layer. The worms will migrate slowly to the food layer. If you have large layers in your bin and you want to harvest casts earlier, you could add a layer of chicken wire instead of a new plastic layer.