black skirt tetras killing neon tetras.


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Jan 15, 2017
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Hello, I have a 55 gallon aquarium with 3 black skirt tetras and got 5 neon tetras. I put in the neon tetras and they acted okay, and all day the fish were in the tank with no problem. At night I turned off the lights and went to sleep. When I woke up I checked mt tank and saw one neon tetra hiding and alive, two dead and on the gravel, one stuck in the filter alive, and one was missing. After seeing what had happened I scooped out the 2 dead tetras and unplugged the filter to free the one stuck in it and one of the black skirt tetras swam over to the tetra, ate its right eye, and killed it. I then isolated the surviving neon tetra (witch wasn't picked on before I could get it), scooped out the dead neon tetra and searched for the one who vanished. I couldn't find it. I want to get some more neon tetras but I don't know what to do. Can someone help me?
Black skirts and neons both need larger school of say 10 or so, which is easily doable in that size tank. The black skirts often become nippy and aggressive when not kept in the right numbers. Also, if the neons were already ill/not doing so hot then any other fish will see that they are weakened and start picking at them. How long have you had the tank and how long for the tetras? Neons are fragile and don't do well in newer aquariums.
The tank is new - I just set up in the last month and it cycled already. I purchased one of the black skirt tetras yesterday, One about a week ago, and one about a year a go but transferred it from a 10 gal to my 55 gal with the one I bought yesterday. The 5 neon tetras went in with the 3 black skirts yesterday.
Hmmm, then I think you might of just had a bad batch of neons with aggressive black skirts. You should add schooling fish in groups rather than just one at a time, that way the 1 new fish doesn't get bullied by the older fish. I would wait a while before trying to add any more neons. Even if the tank is cycled, they still do better when introduced to aquariums that have been running for say, 5 months. You can try getting the neons from a different store, hopefully they have a healthier stock, but I'd still hold off on getting more for a while yet.
Perhaps try getting the number of black skirts up to 7-10 for now and then add any other species that you would like to have, so long as they are compatible. I'd add the neons last.
If the place you bought them at does the even exchange/return thing if the fish happen to die within a certain amount of time, I'd take it back along with his fallen brethren and get a refund. If not, then you might as well keep it until you get him some friends ;)
Maybe you can return the surviving neon in exchange. But before getting into that, there is something else that I'd like to mention, which Demeter has also mentioned, and that is what is going on with your Black Skirts.

Shoaling fish is the term we give to a species that lives in groups of often hundreds if not thousands. There is a real inherent need for this programmed into the species over evolution that I won't get bogged down with now, but can come back to if asked. I'll jump to the problem when you acquire one or two or three individual fish.

The first Black Skirt Tetra you acquired a year ago was living under stress from being alone, and this went on for about a year. This severely stressed fish can be expected to be aggressive, much more than usual for this species. Scientific studies have now proven that shoaling fish kept in too small a group (or alone) develop highly increased aggression; this is about the only way a fish can respond to such stress. And once this occurs, it is not going to reverse. So you have a highly aggressive fish. Then a second is added, and a week later a third. It is rather surprising that both of these survived, frankly, but this may likely be due to the large area (they can swim away from one another), and the inherent aggressive nature of the species itself.

Adding the neons likely inflamed the Black Skirts all the more. If you really want the Black Skirt Tetra in your tank, acquire the full group of 10-12 now, at the same time. This is not going to cause any cycling issue, as the tank is large enough to easily get through this, and the fish will be small. It might, or might not work, with the existing Black Skirts. Alternatively, you could decide to return/exchange the three Black Skirts, and go with a different species. But if you stay with this one, you need 10-12 minimum. Keep in mind though that other species added will have to be agreeable to the Black Skirts; this is not a tetra to keep with sedate fish, or those with long fins, so future options will have to be carefully considered.


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