i have a question after a terrible accident today

[Grim Reaper]

When I got my betta for my 4.4 gallon I also got 3 Celebes halfbeak to go with him after a 3 weeks or so I transfers the celebes to my 28 gallon everyone was happy untill my platys fry’s where releases in to the tank my Celebes started to kill my platy fry’s ( the smallest ones ) none of the other fishes kill them so I decided to transfer my Celebes back to my 4.4 gallon its been 5 months or more that my betta is living own his own so I transferred 1 out of my Celebes to see any violence coming from the betta noting happened so I went to the living room to get the other 2 whiles I was trying to get the other 2 (which are fast as hell), my attention was draw towards the TV which was on and there was a music video clip coming on MTV so I was busy watching the song clip after 5 mins or so I closed the TV catch the Celebes and went to my room just to see the first Celebe in half and my betta feeding from it

Do Bettas turn violent after they stay on they own???

 

[Joby]

I'm sorry to hear about your loss

I guess the betta just saw them as intruders in his territory. I have never introduced new things to my bettas before apart from other females in my community and they well fight or submit to the dominant female. I used to keep corys in the tank with one of my males but after a few weeks he started picking on them. My females however don't have a problem with corys and khulies in their tank.

So I'm afraid I don't know why he turned on them when he'd been living with them peacefully last time. Maybe because it was on its own?

 

[Grim Reaper]

Maybe because it was on its own?

I guess so