I would live to add a goby but my tank is full and my eel eats anytjhing that is eel-like- I guess he is afraid everyone will forget about him. I have a yellow serpant and he dosn't do anything with the sand.
my serpant star which I got 5 weeks ago has moved under a rock from day one and never came out. He is not stuck, and when food is added to the tank, his little legs come out and wave around to grab food. Not much of a tank cleaner. Just a hungry lazy star fish.