My neons chewed off each others tail fins!

[cichlid]

Tonight as I was about to turn off the lights, I was admiring my fish. The jumbo neons were acting somewhat aggressivly and snapping at each others tail fins, much like I would expect from my cichlids, when I looked closer, I realized 4 out of 5 have no tail fins left, the 5th is half way there, all are swimming fine. Has anyone seen this aggression from jumbo neons?

[Gregzz4]

I have, in Cardinals.
I had 9 left of 12 over a year. So I decided to bump up the school.
The originals were store-bought. The 5 I added were probably wild-caught as I bought them from Patrick.
They chased each other out of favourite hiding planted areas and fought for a week before they finally started to school.

[cichlid]

Its wierd, Ive got 9 zebra danios, 3 black skirts.... No problems and both are nitorious fin nippers... Neon tetras they ate each others tail fins

[jobber604]

Behaviour occurs when there us lack of tank space and or under fed fish. Fish become aggressive and hungry towards one another.

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[cichlid]

Well there is tons of tank space, I feed them 2x a day.