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Red-tailed Crown Fish Ecological Habits and Breeding
Aequidens rivulatus, commonly known as the Green Terror, is a medium-sized cichlid native to the freshwater rivers of western and central Peru, as well as parts of Ecuador. This striking fish is popular among aquarium hobbyists due to its vibrant colors, strong personality, and relatively easy breeding habits. Once sexually mature, especially males, they display dazzling coloration, making them a favorite for ornamental purposes.
**Ecological Habits**
1. **Morphological Characteristics**
The male Aequidens rivulatus can grow up to 20 cm in length, while females are generally smaller. Its dorsal fin extends from the back of the gill cover to the front of the caudal peduncle. In mature individuals, the dorsal and caudal fins often turn golden or red. The lower part of the gill cover features bright green stripes, which give this fish its common name, "Green Terror."
2. **Lifestyle and Behavior**
This species is known for being aggressive, especially when mature. Juveniles primarily feed on zooplankton, but as they grow, they become predators that can consume small fish and shrimp. Before reaching sexual maturity, they tend to be more social, but once mature, they become territorial. Males and females form pairs and defend their space. They have high adaptability and can thrive in water with high organic content. Ideal conditions include pH 6.5–8.0, hardness 6–15 dGH, and temperature between 21–25°C. While they can tolerate temperatures as low as 17°C, they require well-oxygenated water and are sensitive to heavy metals like mercury. Therefore, treatments involving mercurous nitrate should be avoided if young fish show signs of disease.
3. **Breeding Behavior**
Like most cichlids, Aequidens rivulatus exhibits strong pair bonding and parental care. They prefer to lay eggs on smooth stones or glass surfaces, though they can also spawn on vertical areas. Before spawning, the pair becomes inseparable and aggressively defends their territory. The male displays more vibrant colors, and both sexes show visible genitalia. Eggs are laid in batches, and the parents take turns protecting them. However, random pairing often leads to aggression, with males sometimes attacking females. Proper identification of males and females based on physical traits is essential for successful breeding.
**Artificial Propagation Methods**
1. **Pairing Broodstock**
During the breeding season, Aequidens rivulatus naturally pairs. Keeping more than ten juveniles in one tank allows them to reach sexual maturity within 8–12 months. Feeding live food accelerates maturation. Once paired, they become highly territorial and may attack other fish. It’s important to remove breeding pairs promptly to prevent damage to other fish. Before spawning, broodstock should be fed live prey such as small fish and shrimp to ensure optimal health.
2. **Spawning Tank Setup and Water Quality**
A suitable spawning tank measures about 0.8m x 0.5m x 0.4m. Smooth stones or glass can be placed inside for egg-laying. Water quality is not overly strict during breeding, but maintaining a temperature of 25–27°C and adding fresh water regularly helps. The tank should remain clean and undisturbed.
3. **Spawning and Hatching**
After adapting to the environment, pairs usually spawn within 1–3 days. The female lays 500–1,500 pale yellow eggs, each about 1.5mm in diameter. Parents guard the eggs closely, and even minor disturbances can provoke aggressive behavior. Fertilized eggs hatch within 1–2 days, and larvae become free-swimming shortly after. Although parents care for the fry, it’s often best to remove them after spawning so the eggs can hatch undisturbed.
**Juvenile Fish Rearing**
1. **Larval Feeding**
Newly hatched larvae are around 0.7 cm long and initially feed on rotifers or Artemia nauplii. As they grow, they transition to finely sieved food and later to live worms. Consistent feeding ensures healthy development.
2. **Juvenile Care**
Juveniles are active and voracious eaters. If provided with sufficient insect-based food, they grow uniformly. Growth slows below 3 cm, but accelerates once they reach 3–4 cm. At this stage, they can begin eating dry food. A gradual transition from live to dry food is recommended, starting with a 3:1 ratio and slowly reducing the live food proportion over five days.
**Feeding and Transport of Adult Fish**
Adults have similar dietary needs to juveniles but require more space. Live foods like small fish and shrimp enhance coloration and growth. Female growth slows compared to males at the sub-adult stage. During transport, adult fish are prone to eye injuries and bacterial infections. To minimize risk, keep water temperature below 23°C and avoid overcrowding. For example, in a 70 cm double nylon bag, no more than 20 fish under 13 cm should be transported. If an eye injury occurs, treat with 0.5 mg/L oxytetracycline or 15 mg/L potassium permanganate for 10 minutes to aid recovery.