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So I stuck my hand in the tank. My brother huge RES comes up and BITES me. Is that normal?

Yes. Turtles really aren't always very human-oriented, and they are always hungry. He was probably protecting his turf and at the same time seeing if your hand was edible.
As RES get larger, their bites get considerably stronger. My one RES is more aggressive than the other, and I just avoid sticking my fingers near her. I don't see any reason to tempt her.

It is normal even if it is a friendly turtle. Anything in water is food to them and they will test it out to see if they can eat it, this happens even more if they turtle is hand fed. My babies go crazy when they see my hands and they start jumping up trying to bite my fingers but after a few bites and they get no food they just sit there and look at me like "what the heck?"

Yep -- Your finger is meat to them. Sometimes they eat things they are not supposed to. b.

Take-One wrote:So I stuck my hand in the tank. My brother huge RES comes up and BITES me. Is that normal?

Totally. Your finger looks like a juicy worm! They honestly can't tell the difference.