Help w/ Aggressive Black Skirt Tetras

[rbeland]

I have a 20 gallon tall tank that has mainly been a community tank (my first). It's been up and running over a year with mainly various tetras such as black skirts, neons, red eyes, and over the months I've mixed in corys, a blue flame gourami, some african dwarf frogs, maybe a couple more different fish. Ultimately the black skirts seemed to rule the tank. Most recently (currently) I have two black skirts. I had one red eye along with them that was being bullied so I just added two more red eyes and now the red eyes seem ok.

I also just added three swordtails. After the first night one ST was gone (eaten I presume), the next night one was killed but not eaten, and this morning the last remaining sword tail has cottonmouth. I don't have a quarantine tank so I just took it out and flushed it. It's all leading me back to the black skirts which I believe killed the blue flame gourami a while back also.

(EDIT - AFTER WRITING THIS I HAPPENED TO FIND THE MISSING SWORDTAIL ON THE GROUND UNDER THE COUCH. IT MUST HAVE JUMPED OUT. PROBABLY SCARED AWAY.)

The tank has a few fake plants, a small castle fish can hide in, and a round rock like structure that they can hide in. Water parameters are fine, ph is around 6.5-6.8. I also have a bunch of zebra snails that help keep the place clean.

So I want to add more fish but I don't want to keep having them die.

Any thoughts? Am I missing something or doing something wrong like mixing the wrong type of fish?

Thanks for any help or advice you can offer.

 

[Masha]

I have black skirt tertas in a 23 gallon tank with swordtails , cories and silvertip tertas.

They are very active and pushy, but never attack the other fish. I believe that this is because I have them in a school of 8.

I know that they are aggressive when there are fewer of them, maybe because then they are stressed and feel insecure.

If you want to keep this kind of fish you are going to have to get more of them to form a school.

You say the water tests fine? So I assume the tank is not over stocked? It sounds a bit overstocked

Next time you need to kill a fish, please don't flush it, the fish suffers that way.

Look up the kinder methods such as using oil of cloves.

 

[Pamiam]

At first impression it sound like a territory issue, I am guessing your tank has too many fish...but you did not say how many of each species you have.

For example the Black Skirt Tetra is a schooling fish and should have at least 7+ members, so are the, neons, red eyed tetra and cory cats. Corys should be in a minimum 30 gal tank but I have found they are happier in a 55 gal.

Just a suggestion mind you.

 

[PNWaquarist]

Corys can be kept in groups as small as four without significant stress and will do fine in a 20-gallon tank. (Though I'd recommend pygmy corys if you're in a smaller tank.)

I agree that the tank is likely over-stocked and that there are likely not enough of each tetra species. Generally speaking, tetras need to be kept in shoals of 6+ to be happy. You can sometimes get around this by mixing different species of the "torpedo-shaped" tetras. For example, my Cardinals and Rummys school together because they're similar in shape and size. In your tank, the Black Skirts are unlikely to associate with the Neons or Red Eyes.

Also, if you need to euthanize a fish, ice water or boiling water will the job more humanely than flushing.

 

[rbeland]

Thanks for the help all. I should have been more clear. I listed fish that have come and gone. I now have 6 black skirts and 3 red eye tetras. I added the three swordtails when I only had two black skirts and one red eye. I liked the sword tails but it sounds like my small number of black skirts lead to the aggression that killed them.

Sent from my SCH-I535 using Aquarium Advice mobile app

 

[Masha]

So you are still having aggression problems even though you have six of the black skirts now?

I have seen forum posts by others saying that they have trouble with these fish being aggressive, although my own experience has been that as long as I have at least six, they leave the other fish alone.

I like my black skirts, but they are very pushy and to be honest, a bit of a pain. It's really difficult to keep other fish with them that are a bit more timid as they chase them away from the food which makes it tricky to ensure that every body gets fed properly.

 

[PNWaquarist]

(EDIT - AFTER WRITING THIS I HAPPENED TO FIND THE MISSING SWORDTAIL ON THE GROUND UNDER THE COUCH. IT MUST HAVE JUMPED OUT. PROBABLY SCARED AWAY.)

Sorry to hear that. Swordtail jumping is normal behavior. If you're going to keep them, definitely get a lid.