Tumbler medium question

I've never used walnut shells. I've seen 'em used on glass bottles to clean them out.

I use white aquarium gravel and a little dishsoap.

Only time I have used walnuts shells was in sand blasting . They were not hard enough to do the job but couldnt tell the boss He was cheap lol They should work ok with coins

Update

I had about 150 Zinclons and the drum was about 1/3 full of walnut shells, then I added 2 oz. of Fantastik cleaner into the mix and let it tumble for 4 hrs.. Separated the coins out and discovered only half were clean. The medium stuck to the side of the drum and I believe the coins were stuck as well, so I will try the dry method. BTW the walnut shell medium was recommended to me by the local detector dealer. I could only get the stuff in a 25lb bag so I'm stuck with it for a while