A hardy nocturnal catfish from South America with bony armor plates, capable of atmospheric breathing and unique bubble nest building behavior
Overview
Callichthys callichthys is one of the most fascinating members of the armored catfish family (Callichthyidae), found throughout the freshwater habitats of South America. This species is widely distributed across the Amazon and Orinoco river basins, as well as in Guyana, Suriname, Trinidad, and southern Brazil. In the wild, it inhabits shallow, slow-moving or still waters — swampy areas, flooded meadows, and ditches with dense vegetation.
The body is covered with two rows of bony plates that form a distinctive "armor," providing reliable protection from predators. Coloration ranges from olive-brown to dark gray, with the belly typically lighter. Adults reach a size of 10–15 cm. Two pairs of long barbels on the upper jaw help the fish navigate murky waters and find food in the substrate.
One of the most remarkable features of Callichthys callichthys is its ability to breathe atmospheric air. The fish periodically rises to the surface to gulp air, absorbing oxygen through the intestinal walls. This adaptation allows it to survive in waters with extremely low dissolved oxygen levels and even crawl short distances overland between water bodies. The species is primarily nocturnal — during the day it prefers to hide in shelters, becoming active at dusk to forage for food.
Tank Requirements
A tank of at least 50 liters is suitable for keeping Callichthys callichthys. Optimal water parameters are: temperature 22–28 °C, pH 6.5–7.5, and general hardness (GH) 6–12. While the fish is quite hardy and tolerant of parameter fluctuations, stable conditions are always preferable.
Fine sand or smooth rounded gravel works best as a substrate — this protects the fish's sensitive barbels from damage. The aquarium should be equipped with plenty of hiding spots: driftwood, ceramic tubes, coconut shell halves, and dense plant growth will create a comfortable environment for this nocturnal dweller. Lighting should be subdued, or shaded areas should be provided.
Since the armored catfish breathes atmospheric air, a gap of 3–5 cm must be maintained between the water surface and the tank lid. A tight-fitting lid is essential, however, as the fish is capable of jumping out of the aquarium. Water flow should be moderate to gentle, replicating the conditions of its natural habitat.
Feeding and Diet
Callichthys callichthys is an omnivorous species with a strong preference for protein-rich foods. In the wild, its diet consists of small invertebrates, insect larvae, worms, and detritus. In the aquarium, the staple diet should include sinking granules and tablets designed for bottom-dwelling fish, supplemented with live or frozen foods such as bloodworms, tubifex, brine shrimp, and daphnia.
Given its nocturnal nature, feeding is best done in the evening, shortly before or after the lights are turned off. This ensures the catfish can eat in peace without competition from daytime tank inhabitants. Feed once daily, offering only as much food as the fish can consume within 15–20 minutes. Avoid allowing uneaten food to accumulate on the bottom, as this quickly degrades water quality.
Care and Maintenance
The armored catfish is a hardy species with a moderate care level. Weekly water changes of 25–30% will help maintain stable water quality. Use a filter with moderate output that provides both mechanical and biological filtration without creating strong currents.
Regularly clean the substrate using a gravel vacuum, paying special attention to areas around hiding spots where food debris tends to collect. Monitor ammonia and nitrite levels — both should remain at zero. Nitrate concentration should not exceed 40 mg/l.
With proper care, Callichthys callichthys lives 10–15 years in captivity. Keep an eye on the condition of the fish's barbels — damage or shortening may indicate overly coarse substrate or poor water quality. The species is generally resistant to disease, but sudden deterioration of conditions can lead to bacterial infections and fungal issues.
Compatibility
Callichthys callichthys is a peaceful bottom dweller that works well in a community aquarium. The fish shows no aggression toward tank mates and spends most of its time near the bottom. It is best kept in a small group of 3–5 individuals, which encourages more natural behavior.
Good companions include peaceful fish that inhabit the middle and upper water levels: neon tetras, cardinal tetras, glowlight tetras, and scissortail rasboras. Cohabitation with other peaceful catfish, such as bronze corydoras and bristlenose plecos, also works well.
Avoid housing armored catfish with large aggressive cichlids or predatory fish that may view them as prey. Keeping them with very small fish is also inadvisable — an adult armored catfish may accidentally swallow fry or tiny fish during its nocturnal foraging.
Breeding
Breeding Callichthys callichthys in the aquarium is an engaging process of moderate difficulty. The most distinctive feature of this species is the male's construction of a bubble nest on the water surface. The male collects air bubbles and plant fragments, building a dense nest among floating vegetation or beneath broad leaves.
To trigger spawning, simulate the onset of the rainy season: lower the water temperature by 2–3 degrees, increase the frequency of water changes, and use soft, slightly acidic water. Add floating plants to the tank to serve as an anchor for the nest. Females ready to spawn can be identified by their noticeably fuller bellies.
After constructing the nest, the female deposits 100–200 eggs into it. The male actively guards the clutch, fanning the nest with his fins and maintaining its structure. The female should be removed after spawning to reduce stress on the male. Incubation lasts 4–5 days at approximately 26 °C.
The newly hatched fry feed on their yolk sacs for the first 2–3 days, after which they begin accepting baby brine shrimp and microworms. As the fry grow, they can be transitioned to finely crushed dry food and small bloodworms.