Coffee grounds are organic in matter, which makes it a perfect food source for worms. Yet, too much of a good thing always has the risk of throwing the conditions in your worm bin off kilter. This can hurt your worms. As usual, there are many factors at play.
A comprehensive list of the common worm farm problems you should be aware of, and possible solutions to resolve each of them.
There's a lot more to worm farm maintenance than you think. But once you get the basics right, maintaining a worm farm is easy and fun.