Knodus borki – Blue Tetra
Knodus borki was officially described in 2008 by Zarske. Knodus comes from the Greek “knodon” = knife, sword, while “borki” refers to the German aquarist Dieter Bork. Their common name is Blue Tetra or Blue Peru Tetra.
Name confusion: The name “blue tetra” can be confusing because several fish, especially Boehlkea fredcochui, are often called this in the trade and the hobby, while in some places even Paracheirodon simulans are referred to by that name. However, the fish offered under that name are rarely if ever Boehlkea fredcochui, that is another fish that shows some similarity with the blue (Peru) tetra. In fact, as far as I can tell, the “real” Boehlkea fredcochui is not kept in aquariums. The description elsewhere in this database of the Boehlkea fredcochui is therefore not correct.
The fish offered commercially (which are fairly rare in the hobby) are Knodus borki. All this was established in 2008 by German ichthyologist Axel Zarske. Based on differences in teeth, shape of the lateral line, and color pattern, he established that it was a different species than Boehlkea fredcochui, which he also described in the same article.
Biotope
Knodus borki lives in the wild in Peru and is mainly found in the Iquitos region. That is in the north of Peru, not far from the borders with Brazil and Columbia.
They live in densely planted, oxygen-rich water, in rivers and streams.
Description
The body is elongated and laterally compressed, and the eyes are relatively large in relation to the head. The dorsal fin starts slightly behind the center of the body, the caudal fin is clearly split.
Their basic color is blue-green to glossy blue, the back is greenish with dark-edged scales. A blue band runs over the sides from the gill cover to the caudal fin. The tail is divided in two by a black stripe or spot. The blue color of these fish is often so intense that many people think that the color is artificial, which is not the case.
The Blue Peru Tetra does not get large: the maximum length is around 5 centimeters. Adult females are slightly larger and have a clearly rounder belly than males. Adult males are a bit more intense in color than females and their anal fin is more reddish in color during the mating season.
Behaviour and compatibility
It is a very lively fish that really needs a slightly larger aquarium than most fish of a similar size. Only then they will show their natural behavior.
Just like most other small tetras, it is a real schooling fish, they must be kept in groups of at least five specimens (preferably 8 to 10 or more). Blue tetras can show some intraspecific aggression, especially if they are kept in too small aquariums. It is better not to keep them together with very vulnerable fish or fish with long veil-like fins, they can also start nibbling fins when kept in too small an aquarium.
In the aquarium, they can best be combined with somewhat similar species such as Danios, small barbels, other small tetras, or small catfish (Corydoras sp.).
The Aquarium
Despite their small size, this is a very active fish and, as stated earlier, it is not really suitable for small aquariums. At least one should give them an aquarium of about 60x40x40 centimeters or 80 to 90 liters.
They thrive best in a densely planted aquarium, with a dark substrate and floating plants that dim the light. If they swim in a tank that is too small, they will not show their most beautiful colors. It is also advisable to combine driftwood or other woody decorations in the aquarium with some dried oak or beech leaves or something similar. By filtering over peat you can achieve that the water gets a similar coloring as in their natural biotope. Furthermore, it is important for Knobus borki that the water is oxygen-rich.
The desired temperature is between 22 and 26 ° C, soft acidic water is essential, the pH value must be between: 5.5 and 7.0 and the hardness may vary from 5-12 °.
If the conditions are well and you take good care of them, the expected life span is around 2 to 4 years.
Diet
Knobus borki is an omnivore. They prefer small live food, but frozen food is also eaten. Dry food – whether or not in flake form – is also eaten without objection. However, it is also important to incorporate vegetable substances in the food, for example in the form of blanched spinach, lettuce, or in good-quality flakes.
Breeding Knodus borki
Although reports show that the fish was bred in captivity, little detailed information is available. I will show what is known below.
Breeding can best take place in a separate breeding tank. This can be filled with soft, acid, and “old” water. The breeding tank can be equipped with a small air filter. A substrate is not necessary, but it is recommended to place a few pots with broadleaf water plants in the tank. The female deposits her eggs on the underside of broad leaves.
The fish must be brought into breeding condition with lots of high-quality live or frozen food. If the female becomes noticeably thicker because of the eggs and the males show their best colors, select the most beautiful pair and place it in the breeding tank in the evening in the hope that they will mate. If you see eggs on the leaves the next day, remove the adult animals because they are likely to eat the eggs or the fry when they get the chance.
The fry are very small and should initially be fed with infusoria.
Video
Author
Menno van Veen
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