Astronotus mikoljii 3–5 cm (Astronotus mikoljii) is a large South American cichlid, closely related to the classic oscar and originating from the Orinoco basin and surrounding areas. Our fish are juveniles of 3–5 cm but will easily reach 30–35 cm as adults, with a heavy, deep body. This species is part of our freshwater range and is suitable only for very large, highly filtered aquariums.

Behavior and care

Astronotus mikoljii is an impressive, intelligent and territorial cichlid. It quickly recognises its keeper and interacts with people outside the tank, but may show strong aggression towards conspecifics and smaller fish. Adults are best kept as a pair or in a carefully planned group, together only with tankmates of similar size and robustness.

We recommend at least 450–500 litres for an adult pair, with a large footprint. A smaller tank may be used temporarily for juveniles, but a larger permanent setup must be planned from the start. The aquarium must provide very strong filtration and good oxygenation (powerful external filters, strong surface agitation). Use starter bacteria when cycling the tank and monitor water values regularly with our water tests. Small fish, shrimps and invertebrates will be treated as prey.

Diet

This species is a large opportunistic carnivore. In nature it feeds on fish, crustaceans, insects and various invertebrates. In the aquarium it readily accepts sinking pellets and sticks for large cichlids, along with frozen foods (brine shrimp, krill, mussel, pieces of fish, bloodworms) and occasional vegetable supplements (green pellets, small portions of blanched vegetables).

For best condition, vary the diet using our foods for large cichlids and feed twice daily (once daily may be sufficient for well-grown adults). Avoid chronic overfeeding to prevent obesity and degraded water quality. We do not recommend routine use of live feeder fish due to disease and welfare concerns.

Water parameters

• Ideal temperature: 24 – 30 °C
• pH: 6.0 – 7.8
• GH: 3 – 15 °dGH
• KH: 2 – 10 °dKH
• Conductivity: 80 – 400 µS

Although hardy, Astronotus mikoljii is very sensitive to ammonia and nitrite spikes, especially in undersized or poorly maintained tanks. Before adding fish, treat tap water with an appropriate water conditioner. Provide over-sized filtration (external filters, often in combination) and maintain the tank with our maintenance tools and large weekly water changes (30–50 % depending on stocking).

Decor and environment

Decor should be simple, robust and secure: a sandy or smooth gravel substrate, plus large, stable rocks and heavy driftwood that the fish cannot easily move or topple. Oscars like to rearrange the decor, so avoid sharp or unstable items.

Plants are often uprooted or nibbled, so limit planting to hardy epiphyte species (Anubias, Microsorum, other plants attached to wood or rock) or protected planting areas. A moderate lighting system with some shaded spots helps reduce stress and highlights the fish’s colours.

Care sheet

AquaBota tip

Success with Astronotus mikoljii depends on a very large tank, powerful filtration and a varied, high-quality diet. Plan for the adult size when buying juveniles and choose tankmates and decor accordingly.
Stability = success: check your water values regularly with our water tests and adjust water-change frequency as your fish grow.

Shipping and delivery of live fish

Fish are shipped with great care in insulated, purpose-designed packaging to ensure their safety during transport.

Delivery methods

• France Express (secure home delivery in France, Belgium and Luxembourg)
• In-store pickup in Sombreffe (Belgium)

Shipping schedule

• Order cut-off: every Monday at 10:00.
• France: shipments on Monday or Tuesday, depending on the destination department, for delivery between Tuesday and Thursday.
• Belgium and Luxembourg: shipments on Monday and Tuesday for delivery between Tuesday and Wednesday.