are there any problems using the 1/8 with the domestic rats?
I've got 1/4 hoppers right now. When i switched over to the hog feed i mixed the blocks in with the hog feed and they never really touched the blocks.
I might give your way a try again. Not sure at this point though, I do like the ease of just dumping the blocks right on top without having to go into the tubs and pour the food in the hoppers.

Thanks for the suggestion though.