Guppy Bullying

[Gigrantor]

Hey Everyone, 

Almost all of my tanks are separate strains of guppies. However, I do have a larger, 55 gallon stocked with about 100-120 mutt guppies. This larger tank started as a snakeskin strain, and then moved to a mutt tank where I would throw all of my "culls" from the other tanks. My question is: Has anyone seen bullying from strain to strain in guppies? Specifically the female "culls" from other strain specific tanks seem to be missing some of their caudal fin.  This has only started to happen recently and the other tank mates (all males and snakeskin females) seem to be doing fine. I know guppies are labeled fin nippers, but I'm a little bit stumped. The only other thing I can think of is that some of the males in the tank are getting a little overzealous with mating. 

Thanks!

[Beardedbillygoat1975]

I have seen our females tend to be aggressive especially as they age. When they get to a certain size and age they stop reproducing much and just get fat and angry. I remove those females as they can really do damage to other fish and predate on their fry. 

[Gigrantor]

I do have 2 or 3 females that have stopped reproducing recently and are easily the biggest in the tank. I will try relocating them to see if that helps! 

[Gator]

Is there a possibility that one or more of your females are not female Guppies, but are female Mosquito fish? The female Guppy and the female Mosquito fish look the same, but with subtle differences in appearances, and the female Mosquito fish is known to be a fin nipper. I've never had a female Guppy become a fin nipper, but I've had female Mosquito fish that were.

[Gigrantor]

I’m 99.9% sure that they’re all guppies because all of them I’ve put into the tank, I’ve seen reproduce. I’ve removed the old gals that don’t seem to be reproducing any longer, and put the victims in a hospital tank with some salt to prevent infection. Just keeping an eye on everything now!