The Wild Habitat
Amazon flooded forests (igapó) form when seasonal rains overflow rivers into the surrounding jungle. The water is dark with tannins, acidic (pH 4.5–6.0), warm (78–84°F), and fish swim among submerged tree roots and fallen leaves.
This is the habitat of cardinal tetras, neon tetras, hatchet fish, angelfish, oscars, discus, and most South American cichlids.
Tank Setup
Tank size: 40-gallon long minimum for a meaningful representation. 75-gallon ideal.
Substrate: fine sand (pool filter sand or play sand). Brown or beige tones.
Hardscape: driftwood (any species, the more twisted the better). Branches and roots from non-toxic woods.
Leaf litter: cover the entire substrate with Indian almond, magnolia, oak, or beech leaves.
Water Chemistry
pH: 5.5–6.5 (lower for Rio Negro biotope).
GH: 1–4 (very soft).
KH: 0–2.
Temperature: 78–84°F.
Most tap water needs RO mixing to soften. Botanicals (almond leaves, alder cones) lower pH gradually.
Plants
Strict Amazon plants: Echinodorus (Amazon swords), Cabomba caroliniana, Eleocharis acicularis (dwarf hairgrass).
Optional: floating plants like Salvinia and Pistia (water lettuce) — natural in flooded forest.
Avoid: anubias (African), java fern (Asian), vallisneria (Mediterranean) — common substitutes but not biotope-correct.
Fish Selection
Cardinal tetras (Paracheirodon axelrodi): 15–20 in a 40-gallon. The iconic Amazon shoal fish.
Hatchet fish (Carnegiella, Gasteropelecus): top dwellers, school of 6–8.
Otocinclus (Otocinclus vittatus): bottom-mid algae eater, school of 6.
Corydoras sterbai: bottom dweller, group of 6.
Apistogramma agassizii or cacatuoides: dwarf cichlid centerpiece pair.
Lighting
Subdued lighting. Tannin-stained water absorbs strong light, so over-bright fixtures look wrong.
40–60 PAR is plenty. Photoperiod 6–8 hours.
Maintenance
Replace leaf litter monthly as it decomposes.
Water changes: 25% every 2 weeks with prepared (RO + botanicals) water.
Don't vacuum the leaf litter — it's the ecosystem foundation.