Congo Tetras becoming aggressive

Molinious

My older Congo Tetras are seemingly becoming aggressive towards the younger Congos and shoo off other fish, also theyve started to hunt down and chase the CRS which they have never done before.

They are usually so placid i dont get the change in temperment.

Is it something to do with breeding or another natural occurance?

Any information would be greatfully taken on board.

Altho this is disturbing shift in behaviour it is also quite comical after theyve just chased another inhabitant they immediately come to the front of the tank as tho there looking at me like a naughty child would

Byron

Probably normal behaviour, but if you could take a video and post it I could be more certain. This species is very active, mine hold relay races down the tank regularly.

dave56

Sometimes fish change temperment as they mature. Usually for no apparent reason. They just become grumpy towards the other fish. This has happened to me several times with different species. If you have enough tank space, you might try increasing the size of the group ti disperse aggression.

jaysee

Exactly.

Congos are pretty aggressive (for tetras) - that sounds like normal behavior to me. Mine (fully grown) are only placid when they are sleeping. Also, their behavior changes throughout the day. There are times when they beat the crap out of each other, and times that they are all just milling around together.

kaythenewbie

How many do you have? When I lost a few black phantoms, the rest (4) became extremely aggressive towards each other and the other fish in my tank. They also began to direct the majority of their aggression toward one specific black phantom in the tank. Once I added more, their aggression spread out and calmed again. Tetra stress out if their in too small of a group.