I had a harelquin for a few years. It was the Australian type and spectacular to look at. It grew to about 8” before I had to rehome it. it will never bother corals. Shrimp will instantly be eaten. Mine ignored snails (at least I never saw him do anything to them). But as the harlequin grows it will eat any fish it can fit into its mouth - clown fish, anthias… any fish! And that it why I ended up parting with it.