aw, cute! i never thought of sticking my hand in there. o.o i'm always paranoid i have some particle of something on me that would make him sick or something...
i do set my finger on the outside of his tank, and then move it over over a little bit, and keep doing that. he likes to come inspect my finger, and then follow it over, and inspect again.
also, when i'm doing a 50% water change, i take the water out, and when i refill, i do so with him still in the tank. i let the water drizzle out in a thin stream and he loves to look at each and every bubble the stream makes on the surface of the water. he is completely not scared of water changes. he loves them. :)