My experience with feeding by hand:
My hatchling, Frankie, used to be very scared of me, and wouldn't even eat in front of me in water, let alone by hand! After about 1 month, he started eating in front of me. My other turtle (Mr. Turtle) is much bigger, about 4 inches, and has always had a very healthy appetite - I take him out the tank to feed and he'll start chowing down on food before I've even let go of him into the feeding dish!
I started feeding them by hand a few weeks ago. If I pinch a turtle pellet between my thumb and finger Mr Turtle will happily grab it out. Frankie was always too scared to do this but I think he saw Mr Turtle doing it and now will.
HOWEVER - Mr Turtle will not try and chew my finger off and will just try and take the pellet. Even when Mr Turtle has accidentally got my finger he didn't latch on or properly bite. I thought Frankie would do the same...also because he is so small, I just stuck a pellet to my finger rather than pinching it between two fingers and.... the little bastard bit me and wouldn't let go (cue me frantically waving my finger around with this cute little 1 inch turtle latched on

). Its odd, I figured he was too small and timid to bite painfully but I was very wrong! Neither will bite if I don't have food stuck to my fingers though
