While I was in Bali, I would make a point to check any sea stars I saw – especially ones with damaged or missing arms – to see if I could find any Harlequin Shrimp as they prey on sea stars.
That was how I got lucky and spotted these tiny Sea Star Shrimp (Periclimenes soror) – did you spot the one above? My ID book says they max out at 3/8 of an inch, which seems a little smaller than the largest one here, but you can definitely see how small the little ones are.