res behavior

Question
I have two RES. One is 5 inches. And the other is 4.5 inches. measuring the shell. Most of the time, I see my bigger turtle push the smaller one out of the way. Since I got them, they have always been pushing each other and being mean. But they also get along with each other very well. But just recently, the bigger turtle pushed the smaller one out of the way, and my smaller one must have been really mad, because he/she tried to bite and probably did bite my bigger turtle's hand. I don't want to separate them because they might be lonely. What should I do. And by the way, is the hand biting thing normal? I feed them and even if they were starving, they seem to tell the difference of food and other very well. Thanks so much for reading!

Answer
They won't be lonely- most turtle species don't like cage mates, and RES REALLY don't like sharing, regardless of what many sources say.

Your options are to separate them, or to house them in a large tank- figure 10 gallons of water per inch of shell length. Right now, for example, you need about a 150 gallon tank mostly filled to have enough room. When they are fully grown, you'll need about 225 gallons.