Agressive Penguin Tetra

[daveg6529]

I have a 260ltr tank fully cycled (over 1 year) with a  50 tetras (small) of various types. I have 10 penguins. Recently one has become unsociable, she spends most of her time in the centre of the tank mid water.
When any of the other penguins come close she chases them away occasionally continues this for some time.
Any ideas as to why?

 

[fluttermoth]

She's probably just the dominant fish in the group. As long as the other fish aren't being hurt, I wouldn't worry.