I have an upwards migration worm composting bin that currently has three trays. In recent months, I had done a poor job ensuring that the moisture level in the top bin was reasonable, and it got out of control and got pretty wet for a while. The worms did not seem to like this.
After several weeks I was able to get the moisture under control. However, the majority of the worms are now in the bottom tray which is mostly already composted material. I don't imagine that there is a whole lot of food/resources in that bottom tray, so they must have been pretty unhappy to move down there and stay there. I also note the middle tray is pretty empty of worms as well.
Is there a good way to encourage the worms to leave the bottom tray and move back up to the top tray where the new food is?