Coffee grounds are OK, but like everything else, you can over do them. They tend to do better after they have aged long enough to develop a white fungus on them. You can be pretty generous with them, as long as you are also feeding other things. I would mix them with the other food scraps, up to 1/2 of the mixture being coffee grounds, and see how the worms respond.

I agree with sbryce that you should let the coffee grounds get really moldy first before adding them to your bin. I have noticed that even in relatively low amounts, coffee grounds begin to drive worms out of the culture. This behavior persisted for 6 days till I added a layer of horse manure and sifted compost to the surface. I suspect the raw grounds are very acidic and mold action neutralizes the pH.

I no longer add raw grounds or kitchen waste directly to my worms. The risk of upsetting the system is too great. Now, I choose instead to add grounds/kitchen waste to my compost pile first. Then, later adding sifted compost to the worms.

"I no longer add raw grounds or kitchen waste directly to my worms. The risk of upsetting the system is too great. Now, I choose instead to add grounds/kitchen waste to my compost pile first. Then, later adding sifted compost to the worms." You may have a point there. We may all be trying to do something that should not be done. The big operators grind and sprinkle a layer that probably includes more bedding. Does anybody know how often a new sprinkle is added and how deep it is? Or how deep the bed already is?

Thanks everyone for your comments. I have read that most of the acidic nature of used grounds is already out in use by humans. I have added starbucks plus my daily home brewed grounds without any effects noticable. I will add that I do add crushed egg shells on a fairly regular schedule as I use them.