Guppy tail nipping

So I got this guppy a few weeks ago and today I see his tail got nipped. I have him in a 15 gallon with some neons, 3 sword tails, some cloud minnows and a betta. And I am not sure who could have done this since my betta has never tried to harm any fish and he doesn't mind them at all

 

Betta. Berttas have poor eye sight. The fancy tail of the guppy might have looked like another male betta to your betta. The betta then attacked the guppy. Make sense?

 

I realize this isn't what you are asking, but I just wanted to mention that you have some stocking issues... your fish have varying temperature needs... and a 15 gallon is pretty small for the current stock. Just wanted to mention this in case you were interested in discussing it. It could lead to more issues in the long run.

 

Could of been easily any of the fish in your tank.

 

I realize this isn't what you are asking, but I just wanted to mention that you have some stocking issues... your fish have varying temperature needs... and a 15 gallon is pretty small for the current stock. Just wanted to mention this in case you were interested in discussing it. It could lead to more issues in the long run.

I should be getting another tank son, so the current setup is mostly temporary

 

The swordtails might contribute to the problem too. My swordtails can’t stand anything with flowy tails like angels or guppies. So they went back to the pet store.