Retroculus xinguensis
Retroculus xinguensis was first described by Jean-Pierre Gosse in 1971. This fish belongs to the family Cichlidae. The genus Retroculus contains three recognized species: R. lapidifer, R. xinguensis, and R. septentrionalis. The generic name “Retroculus” comes from the Latin “retro” (back) and “oculus” (eye), referring to the relatively rearward position of the eye compared to other cichlids. The species name “xinguensis” refers to the Rio Xingu, the type locality of this fish.
Description
General description:
Retroculus xinguensis has an elongated and flattened body with a subterminal mouth (slightly downwards). The color of the head and flank varies from gray to brown with iridescent blue stripes on the caudal fin. The fins are predominantly gray with a black spot on the soft dorsal rays. This fish can reach a maximum length of 31 centimeters.
Differences between sexes:
Males are often larger and have more intense colors than females. No specific behavioral differences between the sexes have been reported.
Behavior and temperament:
Retroculus xinguensis is a peaceful species that lives in groups. They are bottom dwellers and often show “hopping” behavior instead of swimming. They are not shy but can hide if they feel threatened.
Life expectancy:
There are no specific data on the life expectancy of this species in the wild or in aquariums.
Biotope
Natural distribution:
Retroculus xinguensis occurs in Brazil, specifically in the Rio Xingu and Tapajós river basins.
Habitat:
These fish live in fast-flowing, crystal-clear rivers with a bottom of sand, gravel and rocks. The environment has little underwater vegetation and the edges of the water are often bare or lightly vegetated.
Natural enemies:
No specific natural enemies are listed, but they are predators themselves, feeding on aquatic invertebrates.
Climate:
They live in a tropical climate with stable water conditions and high oxygen levels.
Diet
In the wild:
Retroculus xinguensis feeds mainly on aquatic insect larvae such as chironomids, trichopterids and ephemeropteroids.
In the aquarium:
In the aquarium they accept frozen and dry foods, as well as pellets and other commercial fish foods.
Do Not Feed:
Avoid feeding foods that spoil quickly or negatively affect water quality.
The Aquarium
Aquarium size:
An aquarium of at least 200 centimeters in length and 800 liters is recommended for keeping Retroculus xinguensis. For multiple pairs an even larger aquarium is needed.
Setup:
The aquarium should be set up with sand or fine gravel as substrate, and rocks to mimic their natural habitat. Plants are not necessary but can be added for aesthetic purposes.
Water Conditions:
Ideal water conditions are a pH of 6.5-7, a temperature of 25-32°C, and well-oxygenated water.
Compatibility:
This species can live well with other peaceful cichlids such as Geophagus and Satanoperca.
Breeding aquarium and conditioning
Breeding Environment:
There are reports of successful breeding in both regular and special breeding tanks. A breeding tank should be well-oxygenated with a pH of 6.0-6.8 and a temperature of 27-30°C.
Conditioning:
The fish are conditioned with a diet of aquatic insect larvae and commercial fish food. It is not necessary to temporarily separate the male and female.
The spawn
Colors and ritual:
During spawning, the colors of the fish become more intense. The courtship ritual involves digging a hole in the substrate where the eggs are laid and covering it with gravel and stones. Mating usually takes place in the morning.
Eggs:
The eggs are small and numerous, are laid in a cave, and covered with substrate.
Raising the fry
Hatching and free swimming:
The eggs hatch after a few days and the young begin to swim freely after about a week. Both parents care for the young and protect them from predators.
Feeding and survival:
The fry are fed with finely ground fish food and artemia nauplii. Regular water changes are essential for a high survival rate.
Particularities
Retroculus xinguensis is a rheophilic cichlid that has specific requirements for water quality and oxygen levels. They are rare in the trade and difficult to keep due to their specific needs.
Conclusion
Retroculus xinguensis is a challenging but fascinating species for experienced aquarists. They require a large aquarium with specific water conditions and a well-oxygenated environment. Although peaceful, they can be difficult to breed in captivity. Keeping this species can be very rewarding for those who are willing to meet their specific needs.
Video
Author
John de Lange
Copyright images
Enrico Richter – Amazonpredators
