Agressive Tetras!

[FishSticks]

Black Skirt Tetras are one of the first fish that I started keeping, but I didn't know they were schooling fish until a while ago. I originally had 2 Black Skirt Tetras and they seemed quite happy and grew a lot with very long fins in my 10 gallon aquarium.

Later on I decided to add 4 more tretas to make a small school but I didn't want to add them all at the same time because I heard that was bad. First I added the first pair and they started hiding a lot and picked on by the other 2 tetras, later they got along a bit better. 1 week later I added another pair of tretas except this time all hell broke loose!!!

The two bigger tetras I originally had weren't picking on the new fish but they started attacking each other! Their long fins were destroyed! After they seemed to get tired one of the biger tetras started attacking everyone else! So now everyone hides from each other and only come out to eat! They still nip at each other a lot.

Could someone please explain this to me? I thought they were schooling fish!

 

[Lateral Line]

"Schooling" is a protection measure against predators. When "schooling" fish "school" it is because they are nervous, for want of a better word. It does not mean that they WILL school.

In many families, a number of fish put together in an aquarium will have a go at each other to establish a dominant/subordinant relationship. A "pecking order".

A couple of established fish will take a dim view to newcomers, and try to exert dominance, however, the new fish may be more aggressive, so... then add a couple more, and all hell breaks loose. They'll sort it out amongst themselves.

You say "long fins" are these the excessively long finned types, and are all the same type?

 

[FishSticks]

So will they try to exert dominance for the rest of their lifes?

I bought them all at the same place, I'm pretty sure they are all Black Skirt Tetras. They all look the same except the older ones have longer fins, not extremely long. When I bought them it just said Black Skirt Tetra, nothing else.

 

[Lateral Line]

A pecking order takes a while to establish. With some species a few hours, others a few days, others almost never. The thing is, the environment they are in. The fact they were all crowded together in the dealers tank is irrelevent. It is who is there, where they are, now.

 

[FishSticks]

So there's really nothing I can do right? I shouldn't seperate them or anyhting like that?

 

[rollntider]

You say "long fins" are these the excessively long finned types, and are all the same type?

mine was a short fined black skirt tetra and now his fins are real long also, he is getting up there in age(ive had him for 3 years now) and his fins are pretty cool looking. I will have to post pics of them for everyone..... I think they all grow long fins as they age...