Species description

Care, breeding and tankmates

Fish profile

Temperament

Semi-aggressive

The temperament of Corydoras delphax can only be described as completely peaceful and highly gregarious. They are a schooling fish by nature and absolutely must be kept in groups of at least six individuals of their own kind to feel secure. When kept in insufficient numbers, they will become extremely stressed, reclusive, and susceptible to disease. In a proper school, they are active, inquisitive, and highly entertaining to watch as they scurry around the bottom together like a busy little cleaning crew. They pose absolutely no threat to any other inhabitants in the aquarium.

Diet

Omnivore

In the wild, Corydoras delphax is a micro-predator and scavenger that sifts through the substrate for small insects, worms, and crustaceans. In the aquarium, they readily accept a wide variety of high-quality sinking foods, including pellets, wafers, and granules designed for bottom feeders. To ensure optimal health and coloration, their diet should be supplemented with live or frozen foods such as bloodworms, daphnia, and brine shrimp. They are not true algae eaters, so feeding them solely algae wafers is a common mistake that can lead to malnutrition. A varied diet will keep their immune system strong and encourage natural foraging behaviors.

Sex ratio

School

When keeping Corydoras delphax, the exact sex ratio is not strictly critical for their day-to-day well-being, as they do not exhibit aggression toward each other. However, if the goal is to breed them, a ratio of two or three males for every female is strongly recommended. This multiple-male approach increases the chances of successful fertilization during the spawning process. Females are typically larger and noticeably broader when viewed from above, especially when conditioned with high-quality foods. Maintaining a healthy, mixed-gender school allows for the observation of their fascinating natural social dynamics.

Feeding frequency

Twice daily

It is generally recommended to feed Corydoras delphax small amounts of food once or twice a day. The key is to provide only what the fish can completely consume within a few minutes to prevent uneaten food from rotting in the substrate. Because they are bottom feeders, you must ensure that enough food reaches the bottom before faster mid-water fish consume it all. If feeding twice a day, offering a staple sinking pellet in the morning and a frozen treat in the evening works exceptionally well. Observing their bellies can help you gauge if they are getting enough food; they should look gently rounded but not bloated.

Bioload

The bioload of Corydoras delphax is relatively low to moderate, making them an excellent choice for a community aquarium. They do not produce excessive amounts of waste compared to larger or more predatory fish. However, because they are a schooling species and should be kept in groups, the cumulative bioload of the school must be accounted for when sizing the filtration system. Regular water changes and a properly cycled aquarium are still essential to maintain the high water quality they require. It is important to avoid overfeeding, as uneaten food will negatively impact the water parameters.

Flow

Stagnant

Corydoras delphax appreciates a moderate amount of water flow in the aquarium, simulating the gentle currents of their native South American streams. The flow should be strong enough to keep the water well-oxygenated and prevent detritus from settling on the bottom, but not so strong that the fish struggle to swim or rest. Using a standard hang-on-back or canister filter usually provides the perfect amount of water movement. They will often be seen actively swimming against the current for exercise, but they also need quiet resting areas among plants or hardscape. Providing a balance of moving water and still zones is the best approach to their habitat.

Reproduction

Oviparous

Breeding Corydoras delphax in captivity is entirely possible and often highly rewarding for dedicated aquarists. They are egg scatterers, typically laying their adhesive eggs on broad-leaved plants, aquarium glass, or smooth stones after an elaborate courtship dance. To trigger spawning, aquarists often perform a large, cool water change to simulate the onset of the rainy season in the Amazon basin. Once the eggs are laid, the parents provide no parental care and may even consume their own eggs if not removed. For the best survival rate, the eggs should be transferred to a separate rearing tank and the fry fed infusoria or freshly hatched brine shrimp.

Compatibility & tankmates

Corydoras delphax is incredibly peaceful and makes a fantastic addition to most community tanks. They get along well with other peaceful, similarly sized fish such as tetras, rasboras, and dwarf cichlids. It is crucial to avoid keeping them with large, aggressive, or predatory species that might view them as food or nip at their fins. They are also completely safe to keep with most ornamental snails and adult dwarf shrimp, although baby shrimp might occasionally be eaten. Their bottom-dwelling nature means they rarely compete for space with mid- or top-dwelling tank mates.

Tank level

Bottom

As classic bottom-dwellers, Corydoras delphax will spend nearly all of their time foraging and resting on the substrate. They use their sensitive barbels to meticulously search the sand or fine gravel for any edible morsels that have sunk to the bottom. While they are primarily benthic, it is completely normal to see them periodically make lightning-fast dashes to the water's surface to take a gulp of air. Aside from these quick trips to the top, they will almost never be found swimming in the middle or upper levels of the water column. Providing a large footprint with plenty of open bottom space is far more important than tank height.