Just male rainbowfish displaying to each other, it's what they do 90% of the time.
If you want some, get 6-10 fish and have even numbers of males 2 or 4. Males have red fins and tail, females have yellow/ orange fins and tail.
Make sure they have water with a GH around 150-300m and a pH above 7.0.
Feed them lots of plant matter and have a tank that is 3 foot or longer.