I have six Serpae tetras, five rainbowfish, and one Cory cat in a 25 gallon community tank. It is heavily planted. The rainbowfish are a new addition.
The tetras have been fin nipping and killing other fish. So far they have killed 4 fish, one of which was even there before it was. Three dwarf neon rainbowfish and one Cory cat.
How can I reduce this aggression and fin-nipping from the serpae tetras, and provide a safer home for my remaining Cory cat and new (regular size) rainbowfish?