Squirt & Crush

Question
I live in NZ and was given two red eared sliders for my 21st last year. They were only a couple of weeks old i was told when they came from the Pet Store. Now they are six months old. Squirt (3'6" long), has grown very slowly, whereas Crush (5'0" long) has grown rapidly. They were both the same size when i got them. They have very distinct opposite personalities but have always gotten along not a problem. We have just recently added a couple of tiger barb fish as some live prey for them also and they seemed fine. But now they seem to be doing the Jittering thing in each others faces and almost stalking each other around the tank. I have no idea what sex they are yet either. Coould this just be playing or something else as i am sure they aren't mature enough for anything else yet. Any clues would be great. Thanks

Answer
They would be sexually mature at about 4 inches long. Occasional courtship behaviors when younger are  not a big deal. If they do it often, it can be a sign of stress.

The most common stress would be overcrowding or just plain bullying. More space is the common solution.

You can try http://www.redearslider.com for some great info.