Tetras

Silver Tetra and Black Skirt Tetra

The Silver Tetra is very thin, laterally compressed, when viewed head-on and looks like a flattened disk or lozenge when viewed from the side. As in many characins the caudal fin is deeply forked. The anal fin runs from the base of the caudal peduncle forward nearly to the midline, and the dorsal fin is short and somewhat pointed. This species also has an adipose fin, a small fin located between the dorsal and caudal fins. It is nearly impossible to distinguish between the sexes by visual identification alone. Ctenobrycon spilurus has an iridescent quality to its silvery color. A hair-thin band of light greenish runs from the gill cover (operculum) along its side to the caudal peduncle.

This species enjoys a thoroughly planted aquarium filled with soft water, DH 3 to 25, with a pH value of 5.8 ot 6.8. Water composition is not particularly critical for adult fish but the conditons suggested are optimal for best results and especially for breeding. Ctenobrycon spilurus are shoal fishes and should be introduced in groups of four or more (including other similarly sized Tetra species). They are vigorous swimmers and require constant aeration.

Their community manners are somewhat questionable especially in mature individuls. Even young ones may be "fin-nippers". Two immature specimens were living in a community tank when we introduced an infant Aruana. We discovered to our disgust one morning that the Tetras had pecked the "false-barbels" of the Aruana until its chin membrane was ripped completely open. Of course this resulted in the loss of the Aruana. Their reputation for nipping the fins of Angelfishes is legend.

Silver Tetras can be bred and raised in the hobby environment. Prepare a separate, small tank with conditioned water and generous plantings. Feed the chosen mating pair fresh frozen or live food for a week or two while in the community tank. This will condition the female so that when the mating pair are moved to the brood tank she will be receptive to the advances of the male. Raise the temperature in the brood tank to 77°F and adjust the pH to 6.2 to 7.3. The pair should soon begin to vigorously court one another by swimming patterns through the plants. The female will lay 1,000 eggs or more which are immediately fertilized by the male's water-borne sperm. After fertilization of the eggs occurs the parents must immediately be removed from the brood tank. The adults will eat the eggs if left in the brood tank. At 77°F the fry will emerge from the eggs in approximately 24 hours, and should soon be fed a combination of paramecium, rotifers and brine shrimp nauplii. If the fry appear to be outgrowing the available space in the brood tank they should be divided and separated into additional water-conditioned and temperature-equalized tanks.

Tetras are anything but picky eaters. They will eat flakes, bugs, commercial frozen and fresh natural foods. They will eat small guppies if they are in the same community tank. They are fond of small leafed aquatic plants and can destroy a beautifully planted tank in a short time. To minimize this behavior, fresh lettuce leaves may be placed in the tank periodically.

Gymnocorymbus ternetzi is an exceptionally attractive aquarium fish, particularly while immature. Young specimens show black flanks which lighten to steely gray as the fish matures. Black Skirt Tetras have two distinctive black bands running vertically through the body behind the operculum (gill cover) and what appears to be a third, faint vertical band running through its eye. The back is dark greenish in color and the belly is white to silver. All of its fins, excepting the colorless ventrals and pectorals, are translucent black and slightly more rounded than are those of its cousin the Silver Tetra. Fin shapes are otherwise much like those of the Silver Tetra. The female may be distinguishable from the male by comparing the relative vertical measurement between the base of the dorsal and anal fins. The female will be slightly larger and more laterally rounded in this area. Additionally, the male may show whitish spots on its caudal fin which are absent in females.

The taxonomic name Gymnocorymbus ternetzi also applies to the White Skirt Tetra which is essentially the albino version of the Black Skirted variety. The White Skirt is as void of features in its body markings as the Black Skirt Tetra is rich with them. They are identical in their body shape and size. The body color is uniformly white to silver and all of its fins are transparent. These two varieties are genetically compatible (capable of interbreeding) and produce viable offspring.

The water conditions are essentially the same as for the Silver Tetra with a slightly warmer and narrower band of comfortable temperature(73° to 79°), and a slightly wider and more alkaline tolerable range of pH value (6.0 to 7.5). The two species can be kept together with little or no dificulty. Dietary requirements are the same as for the Silver Tetra except that the Black/White Skirt Tetras are entirely carnivorous. Your aquatic plants are safe with them. Breeding procedures are also identical, and the mature fish will likewise eat the eggs and fry.

LinkExchange Member

Gary Churchman
garydebc@silcom.com

Copyright © 1997 Gary Churchman
This page was created Friday, March 14, 1997
Most recent revision Wednesday, July 2, 1997