I'd try it in a corner of the bin and see what happens. If you are caring for your guinea pigs, I doubt there will be enough urine and feces in the bedding to cause it to heat up.

What I would do is wait until the next time I clean out the guinea pig cage, then put a handful or two of their old bedding in a corner of the worm bin and wait to see how the worms react to it. You will probably have to spray it to dampen it.

Thanks for your reply! That is a good idea. I hope they like it!

I'm getting a punch of gpp (guinea pig poop) from a friend in the next day or so. She said her gp's are like machines, they poop so much. It will be "clean" with no bedding.

I've had bunny berries that were mixed in with the recycled paper bedding (Yesterday's News) but I picked out the berries. I figured there would be too much urine in that bedding to use.

Even with the bunny berries I rinsed them thoroughly before feeding. I don't want to take a chance on urine with the worms.

I'll rinse the gpp as well as a precaution.