Description
Freshwater Flounder – Achirus sp.
Introduction
The Freshwater Flounder (Achirus sp.) is an extraordinary bottom-dwelling fish known for its flat, oval body and camouflaging abilities. Reaching sizes of 3–6 inches (7.5–15 cm), this species is a fascinating addition to aquariums with its unique appearance and behavior. Though it is called a “freshwater” flounder, many species thrive in brackish environments, making careful attention to water conditions essential for their health.
1. Natural Habitat and Behavior
Freshwater Flounders are native to rivers, estuaries, and coastal areas across Central and South America. They prefer soft substrates, such as mud or fine sand, where they bury themselves to remain inconspicuous. These nocturnal predators use their camouflage to ambush small prey, making them intriguing to observe in a suitable environment.
2. Aquarium Setup
- Tank Size: Minimum 20 gallons for one flounder; larger tanks are recommended for additional individuals.
- Substrate: Fine sand or soft mud is essential for burrowing.
- Decor: Sparse decorations such as driftwood or smooth rocks. Avoid sharp objects that may injure their delicate skin.
- Water Conditions:
- Temperature: 75–82°F (24–28°C)
- pH: 6.8–7.8
- Salinity: While some species tolerate freshwater, slightly brackish conditions (1.005–1.010 SG) often improve health.
- Hardness: 8–15 dGH
- Filtration: Use a reliable filter with moderate flow to maintain water quality without creating strong currents.
- Lighting: Low to moderate lighting to mimic their natural habitat.
3. Diet and Feeding
Freshwater Flounders are carnivores that require a diet of meaty foods. Offer:
- Live or frozen bloodworms, brine shrimp, and blackworms
- Small feeder fish or ghost shrimp
- Sinking carnivore pellets or wafers
Feed once daily during the evening when they are most active.
4. Compatibility with Other Tank Mates
- Compatible Species: Ideal tank mates include peaceful, non-aggressive fish like mollies, guppies, and other small brackish species.
- Incompatible Species: Avoid housing them with aggressive or overly active fish that may outcompete them for food.
- Social Behavior: Flounders are solitary and generally indifferent to other fish. They can coexist with similar-sized bottom dwellers if space is sufficient.
5. Common Challenges and Tips
- Water Salinity: Many Freshwater Flounders thrive in brackish water, so confirm the species’ needs before purchase.
- Burrowing Behavior: Ensure the substrate is soft and deep enough to accommodate their natural digging instincts.
- Feeding Difficulty: As bottom-dwellers, they may struggle to compete for food with faster, mid-water fish. Use feeding tongs or target feed near their resting spots.
- Water Quality: Regular water changes are critical, as these fish are sensitive to poor conditions.
Conclusion
The Freshwater Flounder (Achirus sp.) is a captivating fish with its flat body and camouflaging skills. Though its care can be specific, the reward lies in observing its unique behavior and subtle beauty. Perfect for brackish tanks or specialized freshwater setups, this species is best suited for aquarists willing to meet its specialized needs.
