Gymnocorymbus Ternetzi (Black Widow)

Freshwater > Fish > Characidae

Gymnocorymbus Ternetzi (Black Widow)

Pics.

Menu

Links

Other

Add

Quick Ref.

Species: Gymnocorymbus Ternetzi

Geo. Location: Paraguay, Bolivia, S.A

PH: 5.8 - 8.5

Temperature: 68 - 79F

Water Hardness: 5 - 19dh

Size: 2.0"

Diet: Worms, small crustaceans, flakes

Difficulty: 1

Photo Credit: Andrzej Zabawski

Notes: First described by Boulenger in 1895, Gymnocorymbus Ternetzi or Black Widow is a very hardy fish. Peaceful and sometimes even shy, this fish is very active. It likes to swim around in the middle and upper part of well planted tanks.
Black Widow (also known as Black Tetra) is not too demanding regarding water conditions. Ph must be included between 5.8 and 8.5 and temperature between 68 and 79F. Optimal ph conditions are between 6.5 and 7.0. It's been reported that this fish can adapt to near cold water temperatures.
Black Widow has a tall and flat body. Several vertical stripes near the head go through its silver body. Its black anal fin is quite developped. This same anal fin becomes clearer as this fish gets older. As a rule of thumb, Gymnocorymbus looses its colors as it gets older. This fish can also loose its colors when it is stressed.
Although Black Widows can be shy, they are territorial and can become aggressive towards other species (especially long finned species like Angelfish, Bettas...). Their attacks are limited to fin nipping and are usually not dangerous to other fish. It is however not recommended to keep Black Widows with other shy or long finned fish. Several hybrids of this fish exist. A white (albino) variety has been described as well as a long finned variety. Some other varieties are colored. Unfortunately, this coloration is not natural and the yellow, green and other purple varieties of these fish have been injected with dyes.
A 20 gallon tank is required to raise this fish properly. Open swimming spaces are important as these fish are always moving. It is best to keep them in school of at least 8 to 10. The tank will have to be well planted with tall plants with narrow leaves. Some floating plants can be added to dimed the lighting. A dark substrat is recommended to keep the light level low. Rocks and driftwood can be added for decoration and hiding purposes.
Black Widow can be kept in specific or community tanks. If kept in community tanks, it is better to keep them with other Characidae or some dwarf Cichlids and Corydoras. Its lisfespan is between 4 and 6 years and as it gets old, Black Widow can become a little more aggressive towards others. It is however a great beginner fish and is sometimes used during the cycle process of a new tank.

Breeding: Breeding Gymnocorymbus Ternetzi is quite easy. Sexual diphormism can be observed on their fins. Males have a larger anal fins and smaller dorsal fins (less pointed) than their counterpart. Males are also slender and smaller than females.
Black Widows are egglayers. A 10 to 20 gallon breeding tank is recommended to succesfully breed and raise these fish. The pair must be introduced in the breeding tank at night as they will probably spawn in the morning. Temperature can be raised to initiate spawning (84F). The male attracts the female by dancing around her. When the female is ready, she spawns between 200 and 400 eggs that the male fertilize (it's been said that he female can spawn up to 2000 eggs in optimal conditions). The eggs are laid among the plants. It is therefore recommended to put marbles or small bushy plants like Java Moss in the bottom of the tank for the eggs to fall into so the parents can not reach them. Indeed, like most Characidae, Black Widows will eat their own eggs if they are not removed from the tank after the spawning process.
The eggs will hatch in 24 hours and after the young fry will have absorbed their yolk sac, they should be feed commercial egglayer food (liquifry), egg yolk and after a few days freshly hatch baby brine shrimps. Before becoming free swimming, the fry attach themselves to a leave or on the sides of the tank. At this point, it is strongly recommended to lower the lighting level in the tank. Indeed, the fry is very sensitive to lighting and a good way to take care of that is to stick dark pieces of paper around the tank. Youngs become sexually mature after eight or nine months.