Name: Gymnocorymbus ternetzi
Origin: South America
The Black Tetra grows a little larger than most other tetra species, but they're just as peaceful and hardy as the others, being quite suitable for beginners. They exhibit the typical tetra behavior of picking on each other all the time, although it never seems to get serious. Their colors vary a lot according to health, mood and lighting levels, only occasionally reaching a really solid black tone. Most of the time their coloration is similar to the picture above. There is also an improved veiltail variety available in shops.
I have kept 4 of these fish in a 1 meter tank with 5 Giant Danios, 2 Zebra Danios, 2 Angels and a Pleco. They are very hardy. However, they are not friendly toward each other in the least! Their colors are much richer in subdued light.
This is one of the easiest tetras to spawn. They are egg scatterers so some kind of a grid on the bottom of the tank to protect the eggs is a good idea. Males are a little more colorful and fins a bit more exaggerated, but if you want a definitive way to sex them, run a wet finger across the anal fin of a netted fish. If it's a male, your finger will catch on tiny hooks on the fin that the male uses to keep the female nearer during spawning. They are not visible to the eye, but they can be felt by this method.
Black Tetras are also known as Black Skirt/Black Snail Tetras. They grow quite large and aren't friendly to each other, but are peaceful to any other fish. Sometimes if you have a larger one and a smaller one in the same tank the larger fish will pick on the other one. They are excellent beginner fish and live for a long time.
I've also got a pair of Black Tetras, and they change colour drastically under different levels of light. Turning on a lamp after a period of darkness usually sees them very black. With normal aquarium lights, they look like those in the picture. When I added white gravel to my fish tank, the strong reflection of the light on the gravel made the Tetras ghost white! Very nice! It's an interesting fish with exceptionally shiny scales.
My Tetras are relatively passive with one another, and I have found that if given enough room, they won't bother one another in the slightest. Their temper comes down to the water levels...I find that the harder the water, around 7.5 - 8.0 (yes 8.0!!!), these little guys tend to thrive, unbelievable but true.