Zebra danio: aggression or just social hierarchy?

[Suzisuzisuzi]

I recently set up a 10g tank for my son. We started with 3 zebra danios to not put too much bio pressure on the tank and just under a week ago added 3 neon danios. The biggest of the original 3 is clearly the dominant fish. Most of the time he's the only one visible, patrolling the top half of the tank and immediately chasing any others (usually a neon) that rise above the aquarium plants and decor. Feeding time is not a problem, the current spreads out food and everyone is up at the top darting after it. But other than that we have 5 hiding fish and one stalking fish.

Is this normal? Should I be worried? Will it calm over time? I'm thinking of catching the bully and exchanging him for another zebra.
Would this help or would another fish take over domineering the others?

 

[sikoko]

Id say a mix of both

 

[Suzisuzisuzi]

I decided to exchange the aggressive danio out for a smaller one. The tank is at peace so far! The usual chasing and playing, bit it's not always the same fish anymore. Different fish start the chasing and more often than not they are all hanging out in a group or two, swimming together

 

[tlindsey]

Sometimes the females are trying to take a break from relentless males lol.

 

[Suzisuzisuzi]

Sometimes the females are trying to take a break from relentless males lol.

If that's the case maybe now I have all girls? Is there a way to tell with danios like you can easily tell with mollies and platys? Cuz I'd prefer NOT to breed

 

[tlindsey]

If that's the case maybe now I have all girls? Is there a way to tell with danios like you can easily tell with mollies and platys? Cuz I'd prefer NOT to breed

I wouldn't worry about it most or all eggs or fry probably won't survive by the adult Danio and other fish in the aquarium.