Black widow tetra

© pisotckii

This small freshwater fish, popular among aquarium enthusiasts, is native to the flowing waters of the Rio Paraguay (Brazil) and the Rio Guaporé (Bolivia) river systems. The fish can grow up to 6.5 cm in aquariums and reach an age of up to 10 years. Individual specimens are said to have reached an age of 12 years.

What are the characteristics of the black widow tetra?

The black widow tetra is an extremely popular ornamental fish despite its inconspicuous but nevertheless contrasting colouring. It is one of the most undemanding characins. Its robustness and easy care make it an ideal fish for beginners.

The appearance of black widow tetra

The silver-colored body flanks of the fish are decorated in the front half of the body by 2 wide deep black cross bands. Through the eye of this fish a vertical dark-coloured bandage also runs. In young fishes the entire back half of the body as well as the dorsal, anal and adipose fins are jet black. The ventral and caudal fins are light coloured. Unfortunately the fish lose their deep black colour with age. This fades and becomes increasingly grey.


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Gender differences

Until reaching sexual maturity (at about 3 cm body length) males and females can hardly be distinguished. After that male and female fish differ in size and width. The females are with up to 6 cm larger than the males with approx. 5 cm and also considerably more bulky. Another distinguishing feature is the dorsal fin. This is more pointed in the male than in the female. The front edge of the anal fin is also wider.

Water values for black widow tetra

As far as the water values are concerned, the black widow tetra is quite adaptable. In the aquarium the pH-values can be 6.0 – 8.0 pH and a total hardness of 5 – 30° dGH. Peat-filtered rather softer water increases its well-being. As an inhabitant of white water rivers, the black widow tetra is not very sensitive to temperature. Water temperatures between 20 and 26° Celsius are completely sufficient.

Feed and nutrition for black widow tetra

The black widow tetra is an omnivore, therefore it can be fed with live and dry food. They particularly like to eat saltwater shrimps, white mosquito larvae or Artemia. The eating behaviour of the black widow tetra is unusual. The fish is a greedy food processor and shoots like mad through the aquarium at every feeding. Other less aggressive fish go out empty.

The ideal aquarium for black widow tetra

The fish feel comfortable in not too bright, slightly shady aquaria. A tank size of 100 L is sufficient for a group of 7-10 black widow tetra. As the fish prefer to stay in the middle and upper tank zone, a larger free swimming space is advantageous. Otherwise the tank should be equipped with some water plants.

Like most fish, the black widow tetra also needs a place of retreat to rest. Plants with large leaves (e.g. Echinodorus species) but also floating plants (e.g. the South American frog bite) are particularly suitable for this. A darker gravel substrate is recommended as substrate.

Keeping conditions

The black widow tetra is a schooling fish and should be kept in groups of up to ten animals. As a peaceful fish it can be well socialized with other equally peaceful fish. However, its roommates should not be much bigger than it itself. Here again the most important keeping conditions in short form:

  • Public tank
  • clear swimming space
  • shady pool areas
  • Peat filtering
  • Live and dried fodder

Characteristics of black widow tetra

The black widow tetra develops with increasing age from a sociable schooling fish to a loner and then likes to retreat into quiet, darker places in the tank, for example under the leaves of larger floating plants.

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