Discus Fish

Geographic Origin and Biotope: The treasure of the Amazon (Peru, Colombia, Brazil). They strictly avoid fast currents. Their stronghold consists of silent bays ('Igarapés'), Blackwater or Clearwater rivers, amidst dense tangles of semi-submerged branches in flooded rain forests.

Taxonomy and Morphology: Member of the Symphysodon genus. The aquatic icon par excellence: the body is literally a perfect disc, extremely laterally flattened (useful for slipping between vines and roots without being noticed). The forehead is steep, small and delicate lips suitable for grazing biofilm. Reaches 15-20 cm (6-8 inches) in diameter. Stationary and slow swimming.

Social Behavior: His Majesty. Discus have a mild, regal, and shy character. They live in rigid hierarchical groupings: they must imperatively live in schools of at least 5 or 6 specimens, under penalty of fatal stress or systematic bullying to the detriment of the weakest. They never persecute other fish in the tank, being placid giants. They can feed from the breeder's hands.

Coloration and Sexual Dimorphism: The pinnacle of hybridization. The original Wild possess warm ochre/brown shades covered by stupendous turquoise vermiculations or black bars (Heckel). Bred varieties range from solid blue (Cobalt Blue, Blue Diamond) to blinding fiery red (Marlboro Red, Pigeon Blood, Red Melon), to spotted patterns (Leopard). They possess conspicuous vertical black bands called 'stress bars' (absent in Pigeon strains) that they use to communicate the state of fear or dominance. Non-existent dimorphism outside of reproduction.

Tank Setup: Demands respect, calm, and volume. Minimum aquariums of 300 liters (75 Gal, better 100+ Gal) and above all TALL (minimum 50 cm / 20 inches of water column). The ideal setup is an essential biotope: very little light, very fine white sand bottom, and a gigantic barrier of hanging roots that covers three-quarters of the glass. They accept thick planted aquariums well, but this complicates the mandatory massive siphoning and hides food debris.

Feeding and Diet: Delicate but greedy omnivore. They forage by blowing water on the sand to flush out larvae. Frequent feeding in small doses. Offer excellent slow-sinking discus granules, top-choice frozen bloodworms and brine shrimp (enriched with preventive garlic and spirulina). Historically, beef heart paste is used, not recommended in community tanks and modern management because it irremediably pollutes the tank.

Water Quality: THE GREATEST OBSTACLE. Discus DO NOT TOLERATE the slightest pollution (Tolerated nitrates close to zero, max 15-20 ppm, absolute zero Ammonium). THEY REQUIRE almost sterile or osmotic water with low conductivity (GH 1-8). The pH must fall on the acidic side: 5.5 to 6.8. Finally, the TEMPERATURE: they live continuously between 28°C and 31°C (82-88°F). A stay at 25°C (77°F) debilitates them in days. Copious weekly (or daily for growing juveniles) water changes are the ritual of every 'Discus Keeper'.

Compatibility and Cohabitation: Roommates chosen with tweezers. Companions must: resist the 30°C (86°F) and never bother them while they eat slowly. Divine roommates: large schools of Cardinal or Rummy-nose Tetras, hatchetfish, Corydoras Sterbai (the only corys resistant to that heat), and rare tame Loricariids. Fast and voracious fish are forbidden, or plecostomus that might try to suck the mucus from their flat flank.

Aquarium Reproduction: One of nature's most admirable parental cares. They lay on a cone, hatching occurs quickly. For the first three weeks, the cloud of microscopic fry LIVES EXCLUSIVELY BY EATING THE HYPER-PROTEIN MUCUS (discus milk) specially secreted by the dark epidermis of the two parents, alternating on the right and left flank.

Risks and Diseases: Disease-catching machines if kept poorly. Intestinal flagellates or Hexamita (noticed by white and filamentous feces, holes in the head), mycosis, stress from hierarchical bullying. A Discus that suddenly becomes very dark (black/gray), remains in a corner facing the wall, is seriously ill.