Crenuchus spilurus: When a tetra is not a typical schooling fish

Not all tetras are typical schooling fish suitable for community aquariums. An example could be the small-mouthed tetras, the most well-known of which isPyrrhulina vittata(The striped slender fish), which spawn on the leaves of plants, and the male then carefully tends to the clutch. It is not afraid of much larger fish that it drives away from its treasure. Others spawn on a flat stone or a pit in the sand (Copeina guttata- Rainbow trout). On the contrary, representatives of the family spawn in the caves.Crenuchidae, to which the species we describe belongs.

Crenuchus spilurus

Crenuchus spilurusIt is a very shy fish that prefers to seek various hiding places in the aquarium. It definitely does not meet the criteria that apply to most common tetras.

Males reliably grow up to 6 cm, females are always 1-2 cm smaller. We can easily keep them in community aquariums, although common literature does not view this idea very positively. As companions, however, we will provide them with peaceful and calm fish of appropriate size. We do not recommend small fish in their company, because they, especially at night, noticeably disappear if our favorites are already bigger.

Origin and environment

It lives in the Essequibo basin in Guyana, but also in the border territory of Colombia, Peru, and Brazil (Rio Yavari). Staeck (1991) found these fish in the Rio Solimoes south of Manaus, as well as in the lower Rio Ucayali (Peru), where they mostly inhabit stagnant or only slowly flowing waters (near the banks of small streams). In July 1987, Staeck found the following parameters in the Solimoes basin: at an air temperature of 31 °C and a water temperature of 28 °C, conductivity was 70 µS, pH 6.9. Both total and carbonate hardness were below 1°dH. In northern Peru, he repeatedly found the fish east of Jenaro Herrera in typical black water, pH 5.5, with a water temperature of 24-27 °C and conductivity up to 14 µS, hardness also below 1°dH.

Description and breeding

A typical feature is both a large mouth that inspires respect, especially among aquarists., on the one hand, the males have beautifully colored and elongated dorsal fins. The fish has been known to aquarists for a long time (Kuntzschmann, 1912), but it has never spread much. Perhaps their shyness is the reason. In a well-planted aquarium with caves and roots, we can't observe them much. Perhaps the reason is also that especially the females are not particularly attractive. Surely, the fact that live food is necessarily part of their good condition will also play a role.It is not always easy to find it. If we want to breed them, it is even a necessity.

I made my first experiences with fish in 1994 when I bought five young individuals about 3 cm long. There were three males and two females. I placed the fish separately in a 45-liter tank, where there were plenty of hiding places among the plants, roots, and in caves. The fish thrived well because I offered them a truly quality menu, alternating between daphnia, brine shrimp, black mosquito larvae, and bloodworms. After some time, even young fish, mostly not very high-quality guppies. A surprising fact for me was that there was no problem with the intake of flake food.

A major disadvantage is the shyness of the fish.As I mentioned before, fish, especially males, constantly seek hiding places. The older the males get, the more they grow into bigger and bigger loners and seek out suitable caves.After a while, they will establish their territories in the aquarium, which they protect through ritual battles. From the original 45-liter aquarium, I eventually removed two weaker males so that the stronger one would have enough energy for the females and wouldn't have to waste it in unnecessary fights with rivals.I often saw the spreading of fins, but also the pushing with mouths, which we frequently observe in cichlids.

Breeding

Sexual maturity is reached at about one year of age. The females will start to fill their abdominal areas, and at this stage, they often stand at the entrance of the burrow where the male lives. It is good to support the fish in this situation by repeatedly changing part of the water, which I eventually adjust to a "neon" form, that is about 20-30 µS/cm, temperature around 27-28°C. I always added a little Torumin so that the water had a hint of very weak tea.

The first friction occurred while the entire group was still living together. Interestingly, both submissive males respected the territory of the dominant male. He ultimately kept a close watch over the clutch consisting of 30 brown (or beef heart colored) eggs, nearly 2 mm in diameter. The clutch was laid on the ceiling of the pot, and the male then transferred the young to a ceramic cave with an entrance about 3 cm wide. The yolk sacs of the young were surprisingly large, initially hanging on the substrate for 3 days before falling to the bottom. Hatching occurred on the 5th day.

Due to the large mouth, I started feeding fine artemia nauplii. However, after 14 days of overfeeding, I made an unfortunate observation that is well known to aquarists breeding red neon tetras in a similar way. The fish had swollen bellies and, except for three individuals, all died during the day. That was a lesson for future breeding. I transferred the young ones to a 20-liter tank for further care.I offered the male a tube with a diameter of 4 cm and a length of 12 cm. When he discovered it, he practically never left it. Only occasionally and for a while, when he set out for food. The females fill up quickly with good care.

After the first spawning, there was another spawning with the second female within a month. At that time, the tank contained regular tap water (120 µS/cm, pH 6.5, 27 °C). The fish spawned earlier than I expected, during the day, and by morning the entire clutch of nearly 50 eggs had gone moldy. In the following weeks, there were repeated spawnings, with the number of eggs fluctuating around 40-60 pieces. Their movement while being fanned by the male was beautiful, as the eggs swayed on the upper and partially on the side walls, creating a stunning wave effect with the entire clutch. A similar scene persisted even after the young hatched, as they were still attached to the spawning substrate.

Breeding is not problematic, the growth of the young is not particularly fast, but we are careful not to provide too large amounts of rich food.I offered the young not only nauplii of small crustaceans but also fine pearls. The presence of a male during the fry's swimming up is important, similar to what happens with the Weitzman tetra.

The first male carried the fry, after they detached from the substrate, to a neighboring and better-protected cave. In subsequent spawns, the fry also detached around the 3rd day and remained lying on the bottom of the tube, where the male periodically refreshed the water for them.young occasionally took in their mouths, as we again see in a number of cichlidsI'm sorry, but it seems that you have not provided any text to translate. Please provide the text you'd like me to translate from Czech to English.I think that is exactly the reason why such cared-for young fish are healthy and resistant to external parasites.

Images:

1. Male 16 months old.
2. Female 16 months old
3. 3-year-old male.
4. 2-year-old male, color variant "Venezuela".
5. Species aquarium with a volume of 45 l.
6. The beginning of spawning in a species aquarium. The female, well prepared for spawning, stands for about half an hour in front of the entrance to the tube, where the male is waiting.
7. The female often stands for hours in front of the tube, which is permanently inhabited by the male (40-liter aquarium), weeks before her own spawning.
8. The male in the nest guards the clutch – front view.
9. The male in the nest guards the clutch – a view from behind.