So I have a five gallon tank with three male Cobra Guppies. One of them is so aggressive the fish its bullying tail is three quarters of the way gone! I need help on why this is happening and how to fix this!
I agree. I would also rearrange some of the things in the tank and give the little ones time to get used to it before putting the bully back in. He will then be the new guy on the block and hopefully won't go back to bullying.they've established a hierarchy and he's the alpha. 5 gallons might be too small for them. can we get a pic of the tank? is there enough stuff for them to hide in?
if you're worried then take the bully guppy out and put him back in later once things have settled down.
My fancy guppy time was a long time ago, but (after a settling in period) a group of males is perfectly doable--in fact, it's how most breeders have their fish. Adding females to the current setup would be a huge mistake, and if the OP is able to set up something larger and wanted to give that a try, they would do best with a 2 female: 1 male ratio, so they would need to get 6 females...which would reproduce and stress the new setup pretty quickly unless they were limited on food and decided to, err, keep their fry's population in check themselves.A 5 gallon is definitely small for Guppies. but do you think that they might also be stressed out by the absent of females in the tank?v