The crushed coral also traps more muck which is of course something which one would prefer not to do for a 1.5G.
My smallest nanos have been 5G but with weekly water changes and LR and LS I had excellent water conditions everytime I tested. 2-3 times per week if you actually get to feeding them. Even if it is a couple cups of water per pwc. Our SW lfs had a tiny vase cube had a little light and some fun things, they changed it up every few months though.
Blue leg Hermits, 1". One problem with Hermts and snails is that they often want to rip the snails out of their shells. Also need to provide a few additional shells for each, in larger sizes.
Don't go for a Halloween or other large sized Hermit though