Threadfin butterfly fish aggression

[A Toadstool Leather]

I volunteer at a small public aquarium and noticed the addition of a pair of threadfin butterfly fish into our tropical tank. They were added at the same time into our fairly large system and got along for a few months until one started attacking the other. I know that these types of fish dont generally get along well with each other but why did the aggression occur months after they were introduced? Its not my job to care for these fish aside from doing basic census and feeding.

 

[Maritimer]

I would imagine that there are a couple of things going on.

The aggressor, in particular, has reached maturity - and the other butterfly isn't acceptable as a mate, for whatever reason. (Butterflies often form mated pairs in the wild, rarely in our tanks.) I can't tell male from female butterflyfish - but they can.

The aggressor is looking out for his/her future mate, should they show up, and wants a nice shiny territory available with all the resources required for producing plenty of gametes.

The competition of the second butterfly for those resources isn't welcome . . .

~Bruce

 

[4FordFamily]

I would imagine that there are a couple of things going on.

The aggressor, in particular, has reached maturity - and the other butterfly isn't acceptable as a mate, for whatever reason. (Butterflies often form mated pairs in the wild, rarely in our tanks.) I can't tell male from female butterflyfish - but they can.

The aggressor is looking out for his/her future mate, should they show up, and wants a nice shiny territory available with all the resources required for producing plenty of gametes.

The competition of the second butterfly for those resources isn't welcome . . .

~Bruce

Agree aggression months later isn’t really uncommon. Unless a pair, adding two of most species is not a good idea. Butterflyfish are no different. It’s always a gamble.

 

[A Toadstool Leather]

I would imagine that there are a couple of things going on.

The aggressor, in particular, has reached maturity - and the other butterfly isn't acceptable as a mate, for whatever reason. (Butterflies often form mated pairs in the wild, rarely in our tanks.) I can't tell male from female butterflyfish - but they can.

The aggressor is looking out for his/her future mate, should they show up, and wants a nice shiny territory available with all the resources required for producing plenty of gametes.

The competition of the second butterfly for those resources isn't welcome . . .

~Bruce

So adding butterflyfish of the same species/genus is generally risky? Where can I learn more about fish behavior like this?

 

[Gareth elliott]

There are not many studies on butterflyfish reproduction.
https://www.hawaii.edu/fishlab/pubs/Tricas & Hiramoto 1989.pdf

This is one i was reading for my own research for a future tank.

There is also two efforts for captive breeding if you search the web. One has managed to successfully breed and raise young. Another has successfully raised captured platonic young.
If you search at least the prior, was published publicly.
The general consensus is that they gender decided at birth and gonad development is delayed until a maturation point or gonad development is decided by environmental factors at a maturation point. The latter would allow for the procurement of small juveniles to create a pair.
This is speculative as again only study of gender acquirement in the wild of butterflyfish is the one above. Every pair I have seen for sale were collected as pairs.

 

[ReefTeacher]

I have been keeping butterflies for years. Some species are more aggressive than others, the threadfin, yellow-head, and pakistani are all quite aggressive IME. On the other hand, I have had groups of pearl scales that are quite docile and friendly; and the same goes for pyramid.