Neon Tetras vs. Cherry Barbs?

I have a school of both neon's and rosy barbs and I have found that if my school of rosy barbs get a bit low, they can become a little aggressive with each other. If I have around 8 or more they are pretty calm. I have not had any aggression from my neon's. I have not encountered any disease from my neon's and some of my neons are 3 years old.