Juvenile Borellii (1.5 cm) aggression?

[Andrew H]

I’ve got 6 borellii pantanal that are 1.5 months old and about 1-2 cm in size now and doing well. They’re still with their mother which seems to be fine (and she remains quite yellow). No other fish - they have one side of a divided 60 gallon all to themselves. The juveniles started displaying at each other in the last few weeks and doing some chasing / striking each other (territorial stuff). I don’t think there’s any damage being done (can’t see any fun damage or “defeated” behavior) but wanted to check with the experts if this is anything to be concerned about.

 

[Mike Wise]

It occurs in my grow-out tanks, too. I generally only get concerned when some fish start to hide at the top of the tank.

 

[Andrew H]

Great, that’s what I was hoping to hear, gives me some more time to make arrangements for them. Seems like training exercises right now. One of the kids even tail slapped the mom who is probably 10X its mass, and which she ignored. Teenagers…

 

[Andrew H]

Great, that’s what I was hoping to hear, gives me some more time to make arrangements for them. Seems like training exercises right now. One of the kids even tail slapped the mom who is probably 10X its mass, and which she ignored. Teenagers…

Oh, and at what size is it reasonable to be able to sex them? Right now the only difference I can see is that some of the them have a black fringe at the the very tips of their dorsal fins.

 

[Apistoguy52]

Oh, and at what size is it reasonable to be able to sex them? Right now the only difference I can see is that some of the them have a black fringe at the the very tips of their dorsal fins.

1” in size makes for easy sexing, although at around 1/2” in size you may start to see some females swimming broods of their own around. They’re “sexually mature” well before they’re easily sexed.