Playing or Fighting?

[jmm]

I've had a couple of butterflies for a little over two years. They were bought tiny and have probably about doubled in size. One is a Burgess and the other is a Declivis. They're considered peaceful fish and have co-existed all this time.

Before they are fed they swim next to each other and are totally non aggressive. However, shortly after they are fed they start chasing each other. Fast. Almost too fast to see. They dart around the tank just fractions of an inch apart, one right behind the other. Instantly, the chaser turns, again too fast to see, and becomes the chased. It is an instant reversal of which is chasing which. They always do this after eating. And then, one will lie in hiding, waiting for the other to happen by and the chase is on again. Neither is dominant. The roles are reversed at high speed.

No marks of any kind have ever shown up on either fish. They are clean, unbitten, and unscratched.

What's going on here?

 

[SAT]

As long as the fins remain intact, I would treat this as just blowing off steam. There's a possibility you're seeing some sexual behavior, now that they are probably adults.

 

[scooter31707]

I agree. What size tank do you have? I had this happen to me one time before. Fish got along fine at smaller sizes, once they it maturity and grew bigger, the aggression got worst.

 

[jmm]

I agree. What size tank do you have? I had this happen to me one time before. Fish got along fine at smaller sizes, once they it maturity and grew bigger, the aggression got worst.

There are four fish in the tank. A long-nose yellow butterfly, Declivis, Burgess, and a juvenile Regal Angel. The angel is slightly smaller than the other three. The tank is a 120 gallon with oversized sump and protein skimmer. All the fish went in from living peacefully in a smaller quarantine tank over about a week's introduction time. There was never any sign of any disease on any of them and they all ate hour one in TTM (4-stage) quarantine. After TTM they went into 6-week quarantine (observation) in a bare bottom, PVC decorated cycled tank. The 120 was cycled when the fish went in. They have doubled in size since introduction about two years ago. They all eat frozen and pellets and nobody has ever had any fin or body damage. Only the two butterflies mentioned interact.

 

[isdaboy]

Nice collection of fishes. It's possible that since the two are closely related and very similar in size that they are now just establishing dominance. Hopefully they will settle in once it's been established, who know, they may pair up. Good luck.

 

[jmm]

I would like to add a Mitratus but I worry about compatibility. Even though the color is different, the body shape and the pattern of coloration is similar to the Burgess. I don't want to press my luck with such expensive fish.