Mikolji's oscar

Astronotus mikoljii

Also known as Astronotus mikolji, Orinoco oscar

FreshwaterFish

Care at a glance

Temperature: 77–86°F (25–30°C)
pH: 5.5–7.2
Adult size: 11.4 in (29 cm)
Minimum tank: 132 gal (500 L)
Temperament: Aggressive
Social behavior: Solitary
Tankmates: Tankmates with caution
Swim level: Middle
Difficulty: Difficult
Breeding: Hard
Rarity: Rare
Origin: Orinoco basin and Gulf of Paria drainages
Family: Cichlidae

Overview

Mikolji's oscar is a large, aggressive predator, so keep it on its own or as a single proven pair rather than in a group. It cruises the middle of the tank and will eat any tankmate small enough to swallow, so choose companions with real care: only big, robust fish stand a chance, and many keepers simply keep it alone. Feed meaty foods such as prawn, mussel, earthworms and quality pellets, and expect a lot of waste, so run strong filtration and keep up with water changes. This is a fish for a tank of at least 500 liters, and a long-term commitment.

In the wild

Astronotus mikoljii comes from the Orinoco basin and the Gulf of Paria drainages of Venezuela and Colombia, where it lives in warm lagoons and slow river channels. Recreate that with warm, soft to neutral water: a temperature range of 25–30 C and a pH of 5.5–7.2. Give it open swimming space with a sand floor, some large water-worn wood or rock for cover, and robust or artificial plants, since an oscar of this size treats soft plants as salad and redecorates to taste.

Good to know

Astronotus mikoljii belongs to the cichlid family and reaches about 29 centimeters. It was described in 2022 and named for Ivan Mikolji, the Venezuelan explorer, artist and underwater photographer, and it is the Orinoco's own oscar, long confused with the widespread Amazonian Astronotus ocellatus. Like other oscars it is a biparental substrate spawner, but it is rated a hard breeder in aquaria because it needs size, a settled pair and clean water to spawn.

Did you know

The team that described the fish in 2022 was led by the Venezuelan ichthyologist Oscar Lasso-Alcala, so the naming was billed, only half in jest, as an Oscar describing an oscar.