My Hippo won't eat from my hand, but he is super aggressive when it comes to feeding, he has bitten me before trying to get at food. He always seems to know though when I am trying to hand feed, because he won't approach, but if I am just casually putting in the food, he has bitten me before.
My Hippo is crazy though about food, he eats so much that as he eats he is doing his business if you know what I mean, as if he is making room, HA HA. I have to spread the food out all across the tank so that the other fish have a chance!