Hoplisoma knaacki
Hoplisoma knaacki was first described by Luiz Fernando Caserta Tencatt and Hans-Georg Evers in 2016. This fish belongs to the family Callichthyidae, which consists of the subfamilies Corydoradinae and Callichthyinae. Corydoradinae is the largest subfamily within Callichthyidae and includes over 200 species. The genus name Hoplisoma means “armored body” and the species name knaacki is a tribute to Dr. Joachim Knaack, a German ichthyologist and aquarist.
Before they were officially described they were known by the temporary name Corydoras sp. CW032.
Synonym: Corydoras knaacki.
Description
Hoplisoma knaacki has an elongated body with a conspicuous black longitudinal stripe along the midline of the flank. The head is covered with round black spots, and the fins are translucent with black spots on the dorsal fin. The fish can reach a maximum total length of 5 centimeters.
Differences between males and females: Females tend to be larger and plumper than males. Males tend to have more pointed fins.
Behavior and temperament: Hoplisoma knaacki is a peaceful, schooling fish that is best kept in groups. They are bottom dwellers and like to dig in the substrate in search of food.
Life expectancy: In captivity they can live for about 3 to 5 years.
Biotope
Hoplisoma knaacki is native to the Río Madre de Dios basin in Peru. They live in shallow, swampy areas with lots of underwater vegetation and shade from trees. The soil is mainly sand and mud.
Natural enemies: Specific natural enemies have not been documented, but larger predatory fish may threaten them.
Climate: They live in a tropical climate with seasonal flooding.
Diet
In the wild, Hoplisoma knaacki feeds on small invertebrates and detritus. In the aquarium, they can be fed sinking pellets, frozen foods such as mosquito larvae, and live foods such as daphnia and tubifex.
The Aquarium
An aquarium of at least 60 centimeters and 60 liters is suitable for a small group of Hoplisoma knaacki. For multiple pairs, a larger aquarium of at least 100 liters is recommended. The aquarium should be set up with fine sand as a substrate, with many hiding places such as rocks and wood, and dense planting.
Water parameters: Ideal water parameters are a pH of 6.0-7.5, a temperature of 22-26°C, and a hardness of 2-12 dGH.
Compatibility: They can live well with other peaceful fish such as tetras, small cichlids, and other Corydoradinae species.
Breeding aquarium and conditioning
For breeding, a special breeding aquarium of about 40 liters is recommended, with soft, acidic water and a temperature of 24-26°C. Use a sponge filter and provide dim lighting. Condition the fish with live food such as black mosquito larvae and daphnia. It is useful to temporarily separate the males and females and then bring them together for breeding. A ratio of two males for one female is best.
The spawn
During spawning, the fish’s colors become more intense. The mating ritual involves the male chasing the female and leading her to a suitable place to deposit the eggs, usually on leaves or glass. Spawning usually takes place in the morning. The eggs are small, round and light yellow.
Triggering Spawn: Spawn can be triggered by simulating rainy conditions, such as lowering the water temperature and adding fresh, cool water. This mimics the natural conditions the fish experience in the wild during the rainy season.
Spawn and T-position: Spawning in Hoplisoma knaacki occurs in the characteristic T-position, which is often observed in Hoplisoma and Corydoras species. In this position, the male positions his body perpendicular to that of the female, using his pectoral fins to embrace her. The female then takes up sperm in her mouth and fertilizes the eggs internally before depositing them on a suitable substrate, such as a leaf or smooth surface.
Raising the fry
The eggs hatch after about 3-4 days. The fry start to swim freely after about 5-7 days. There is no parental care after the eggs hatch. The first food for the fry consists of infusoria and later artemia nauplii. Water changes should be done regularly to keep the water quality high.
Particularities
Hoplisoma knaacki is a relatively new species that was only scientifically described in 2016. They are rare in the trade and are often confused with other Corydoras species due to their similar appearance:
- Hoplisoma bondi: This species has a similar color pattern to H. knaacki, but can be distinguished by the presence of irregular black spots on the head, while H. knaacki has round black spots.
- Hoplisoma sipaliwini: This species also has a similar color pattern, but the spots on the head are larger and less regular than those of H. knaacki. In addition, the black stripes on the caudal fin of H. knaacki are thicker and more clearly defined.
- Hoplisoma coppenamensis: This species has a similar appearance, but can be distinguished by the presence of a well-developed ventral laminar extension of infraorbital 1, while in H. knaacki it is moderately developed. Also the black stripes on the caudal fin are thicker and more clearly defined in H. knaacki.
This confusion is common in the aquarium trade, where these species are sometimes offered under the same or similar names.
Conclusion
Hoplisoma knaacki is an interesting and peaceful fish species that is suitable for both beginners and advanced aquarium enthusiasts. They are easy to keep and breed in a well-equipped aquarium. Their peaceful nature makes them suitable for community aquariums with other peaceful species.
Author
John de Lange
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