I tried big snails and big hermits when I had my dog puffer. He would nip on them but they lived. Mine were not that active but I attribute that to high nitrates since the tank had been up over 7 years with the same CC
I did sell the tank and the puffer though to prepare for reef tank I now have. I have one snail that is still kicking and he had been in the puffer tank for almost 2 years
*180 gal Display, 100 gal basement sump, 33 gal refugium, 3x250 MH, 2x160 VHO actinics, zoos, some softies, LPS & lots of acros and other SPS.
*100 gal prop tank plumbed into main system w/ 2x96 PC lights and 1x150 MH,