what has attacked my fish

[skargo2009]

So one of my endler guppies is missing most of its tail. I need to know who did it. It is in a 10 gallon with another endler, 5 ghost shrimp and 5 neon tetras. I'm getting a betta today which is going in the 10 gallon and I need to know which fish or shrimp ate the guppies tail incase they so the same thing to my betta

 

[NigelK8485]

So one of my endler guppies is missing most of its tail. I need to know who did it. It is in a 10 gallon with another endler, 5 ghost shrimp and 5 neon tetras. I'm getting a betta today which is going in the 10 gallon and I need to know which fish or shrimp ate the guppies tail incase they so the same thing to my betta

Getting a betta if you already have a fin nipper in the group doesn't seem like the most responsible choice. While it's not extremely common, neon tetras have been known to pick apart some betta fins, could possibly be them but it seems like you would have observed it. Are both guppies male? Can you take a picture or look up fin rot and make sure it's not that? It'll tear away the fins but leave the rays and usually the edge will be white or a different color.