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. My 2 Black Tetras are about 4 cm, and 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.