introducing a new turtle to the tank

Question
I have 4 RED EAR SLIDER turtles. I got 3 of them about 15 years ago and they have thrived ever since. About 5 years ago a friend of ours "dropped off" her son's turtle because they could no longer take care of him. We believe the ones we have are females and the one they brough is male. When we first put him in the tank the other turtles started biting him so we put him in another tank by himself. Ever since, he's been in another tank. Now, we have a brand new tank for the 3 big turtles and we want to see if they can share again. The male saw the new tank and jumped in it (there is a ramp from the ground into the water). The male saw the ramp and the other turtles there and jumped in. He started to chase one of them (they are twice as large as he is) and started to try to bite her on the face. Another of the larger turtles came over and started to nip at him. And this went on for a few minutes until we pulled them apart. Is this an indication that they cannot be together??

Answer
Hello Paula,

Yes, if the fighting doesn't stop after a while you probably should keep them in different tanks (Or divide the big tank into 2 halfs).
Turtles usually fights against each other if they feel threatened or if they aren't completely used to it's surroundings.

My advice to you is: Try one more time to put him in the tank with the other turtles and wait for maybe 1/2 - 1 hour, just to see if they calm down. If they still continue to fight, then separate them.
Fighting can cause some really nasty wounds, so you'd better keep them apart if they don't get along.

Best wishes
Sara