Geophagus steindachneri

Adults reach a length of 11 to 15 cm. The coloration of the fish can vary from yellow to red tones, depending on their specific region of origin. Males are generally larger than females and are distinguished by a characteristic 'nuchal hump' on their head.

The species originates from South America, localized in modern-day Colombia. These fish inhabit the Magdalena River basin and its main tributary, the Cauca River, located in the northwest of the country. Although they can be found in various biotopes, Geophagus generally prefer sections of rivers flowing through tropical forests, as well as quiet backwaters with sandy substrates.

Adult males display aggression towards each other, so only one male should be kept in an aquarium, accompanied by two or three females. They are peaceful towards other fish species, demonstrating compatibility with non-aggressive fish of comparable size.

For keeping 2–3 fish, an aquarium of at least 250 liters will be optimal. The decor can simply include a sandy substrate and a few pieces of driftwood. Avoid adding small stones or pebbles to prevent them from getting stuck in the fish's mouth during feeding. Dim lighting is recommended. Aquatic plants are not an essential element, but if desired, undemanding and shade-loving varieties can be planted. If breeding is planned, one or two flat, large stones should be placed on the bottom, which can serve as potential spawning sites. Geophagus steindachneri requires high water quality with specific hydrochemical parameters — slightly acidic, with low carbonate hardness, and a significant content of tannins. In their natural environment, these substances are formed by the decomposition of leaves, branches, and roots of tropical trees. In an aquarium, tannins can be introduced using leaves from certain trees, but this method is not always optimal, as leaves can clutter the substrate, which serves as a 'dining table' for Geophagus. A more preferable option is to use special essences containing concentrated tannins, where a few drops can replace a handful of leaves. The filtration system plays a key role in maintaining high water quality. When feeding, the fish stir up suspended particles that can quickly clog the filter material, so consulting a specialist when choosing a filter is essential. They can help select a specific model and determine optimal placement to minimize clogging. Regular aquarium maintenance is also very important. At least once a week, 40–70% of the water volume should be replaced with fresh water, and organic waste, such as food remnants and excrement, should be systematically removed.

These fish feed at the bottom: they sift through sand in search of small plant particles and various organisms such as crustaceans, larvae, and worms. In a home aquarium, Geophagus steindachneri readily accept various sinking foods. These can be dry flakes and pellets, supplemented with pieces of bloodworms, shrimp, mollusks, as well as frozen daphnia and artemia. It is important that food particles are small and contain plant-based components.

Males are polygamous and may form temporary pairs with several females during the breeding season. For spawning, the fish use flat stones or other smooth, hard surfaces. The male initiates courtship, which can last several hours, after which the female lays eggs in batches. Each batch is immediately taken into the female's mouth, and in the short time the eggs are on the stone, the male manages to fertilize them. Ultimately, the entire clutch ends up in the female's mouth and remains there throughout the incubation period, which lasts 10–14 days, until the free-swimming fry emerge. In the first days of their lives, the fry stay together and instantly hide in their safe refuge if danger arises. This mechanism of offspring protection is not unique to this species; it is widespread among cichlids of the African continent inhabiting Lakes Tanganyika and Malawi.

The main cause of diseases often lies in the keeping conditions: if they go beyond acceptable limits, immunity decreases, making the fish vulnerable to various infections inevitably present in the environment. At the first suspicion of illness, it is important first of all to check the water parameters and ensure there are no dangerous concentrations of nitrogen cycle products. Often, restoring normal, suitable conditions promotes recovery. However, in some cases, medication may be required. Detailed information on symptoms and treatment methods is presented in the "Aquarium Fish Diseases" section.

When selecting individuals in a store, pay attention to the fish's activity and the condition of its skin. A healthy Geophagus should show curiosity, actively explore the substrate, and have no visible damage, ulcers, or film on its scales. Avoid specimens with sunken bellies, signs of emaciation, or unnaturally bloated abdomens, as well as fish that stay near the water surface, which may indicate gill problems or general health issues.

Since this species is prone to intraspecific aggression, it is recommended to assess the number of individuals in the store's aquarium beforehand. It is better to acquire a group of young fish to establish a natural hierarchy or an already established pair. When purchasing, it is worth clarifying the age of the fish, as males begin to show pronounced territoriality and develop the characteristic nuchal hump as they mature. Ensure that there are no signs of ichthyophthiriasis (white spots on the body) in the sales conditions, as this species is sensitive to infectious diseases under stress.