PurpleHeys

Just got these fish on Friday. I've got three cherry barbs in my 10 gallon tank. One of them, who is very pinkish red, is really aggressive towards one of the other fish. It seems as if they've established a boundary or something. They typically hang around the bottom of the tank, and the aggressive one stays on the right side. The other two stay on the left. When food comes, they all come out and eat together and then they retire to their opposite corners.

The other two fish stay on the opposite side, but the smaller of the two will swim to the middle sometimes or even venture over to the far right side where the pinkish one spends time. If the pink one sees this one, he chases him all the way back to his corner, nipping his fins all the way.

If the other fish comes over there, he doesn't bother that one nearly as much.

There are five different pieces of decor in the tank. On the left, there is this little mountain thingy, with a cave in it. And there's a fake plant. Then there is a plant in the middle and two other plants in opposite corners on the right side.

Any idea if this is normal behavior?

capekate

Hello PurpleHeys and welcome to fishlore~

Cherry barbs are very kewl looking fish and I can see why the interest in them. Good luck with them in your tank...
As far as the behavior of your fish I have a few ideas. It seems from what you tell me that it is very possible that you have one male and two females.
The more brightly colored red barb is most likely the dominate male and defending his territory. The other two or either both females, one being the smallest is a juvenile and not at the time a real threat or interest to the male, or a juvenile male.
The other barb is most likely a female that is not a threat to the male and is why he will tolerate its coming over to his side from time to time.
Barbs do like to be in groups but I do not believe you should have more than the three in your ten gal as it is.
If there are no real injuries my guess is that they will have to work it out amongst themselves, learning what side of the tank to stay on and when to get out of the males way!
You can also try putting some of your plants into clumps that the smallest one can sort of hide behind if it gets bothered.

~ kate