I keep two Butterfly fish and also have 4 Hatchet fish. They all seem to get on fine....
Sometimes they may get in each others way, there wil be a quick flick of a tail and everyone scatters, but thats it and its all back to "hanging around" at the surface.
Also,
- ABF can grow up to about 5" (mine are about 3" at the moment, but have seen some in shops at around the 5" length)
- They do sometimes swin lower down in the tank - but this mainly happens when im cleaning and they get a bit freaked out. Sometimes they will dart back and forth only a few inches above the bottom of the tank. I try to keep this to a minimum as they clearly dont like it.
- Ive had these fish for about 2 months and have never had a jumper - ive noticed them leap out of the water only on a couple of occasions, each time they barely made "air" (im not saying that this doesnt happen, just not with as much regularity as maybe published)
- I have a male and a female ABF, the first time they met they immediately locked jaws (he grabbed her lower jaw, she grabbed his upper jaw) and spun around for about 10 mins. It looked as though the female came out the winner. She seems to wear the trousers in that relationship.