Discus is one of the most stunning freshwater fish, demanding stable water parameters and attentive care, yet rewarding its keeper with incredible grace.
Overview
Symphysodon aequifasciatus is a legendary cichlid from the Amazon basin, rightfully called the "king of the aquarium." This species belongs to the family Cichlidae and in the wild inhabits slow-moving rivers and flooded forests of South America, hiding among driftwood and fallen leaves. Discus reaches a size of 12–15 cm and with proper care lives for 10–15 years.
The body of the discus is strongly compressed laterally, forming its characteristic disc-like shape that gave the fish its name. Coloration varies from greenish-brown to bright blue, with vertical dark bars whose intensity changes depending on the fish's mood. Decades of selective breeding have produced numerous color variations: red, turquoise, cobalt, pigeon blood, and many others.
Discus are shoaling fish with a well-developed social hierarchy. They form groups within which they establish ranks without serious aggression. Watching their unhurried, graceful movements is a true pleasure.
Tank Requirements
A group of discus requires an aquarium with a minimum volume of 200 liters. Optimal water parameters: temperature 27–30°C, pH 6.0–7.0, general hardness (GH) 1–8. Parameter stability is critically important — discus are extremely sensitive to sudden fluctuations.
Filtration should be powerful yet create minimal current, as discus dislike strong water flow. An external canister filter with a turnover rate of 4–6 tank volumes per hour is the optimal choice. A heater with a precise thermostat is essential, since even a brief temperature drop below 26°C can trigger illness.
Aquascaping for discus is a debated topic. Many experienced breeders prefer keeping discus in bare-bottom tanks for easier hygiene. However, in a display aquarium, fine sand, driftwood, and shade-tolerant plants such as Anubias, Echinodorus, and Cryptocoryne work well. Bright lighting is undesirable — discus prefer subdued, diffused light.
Feeding and Diet
Discus are omnivorous fish with high demands for food quality. The diet should be based on specialized discus granules or flakes enriched with carotenoids to maintain vibrant coloration.
Frozen foods make excellent supplements: brine shrimp, bloodworms, daphnia, and glassworms. Many breeders prepare so-called "discus mince" — a mixture of beef heart, seafood, spinach, and vitamin supplements. This is a highly nutritious food, but it should be given in moderation to avoid polluting the water.
Feed discus 2–3 times daily in small portions that are consumed within 3–5 minutes. Leftover food must be removed immediately — in warm water, organic matter decomposes very rapidly, promoting bacterial growth and deteriorating water quality.
Care and Maintenance
Discus is not a beginner's fish. The care difficulty level is maximum, and justifiably so — any negligence can lead to disease.
Weekly water changes are mandatory. It is recommended to change 25–30% of the volume 2–3 times per week, using water of the same temperature and parameters. Many experienced aquarists install automatic water change systems, which greatly simplify maintenance.
Water parameter monitoring should be regular: test pH, ammonia, nitrites, and nitrates at least once a week. Nitrate levels should ideally be kept below 20 mg/L. Substrate vacuuming is an important part of maintenance, especially in tanks with gravel or sand.
Discus are prone to several diseases: hexamitiasis (hole-in-the-head disease), ich, and bacterial gill infections. The best prevention is stable water parameters, high-quality nutrition, and quarantining new fish before adding them to the main tank.
Compatibility
Discus are peaceful fish (aggression level — 2 out of 5), but their specific temperature and water quality requirements significantly limit the choice of tankmates.
Ideal companions are small characins that tolerate high temperatures well: cardinal tetra, neon tetra, ember tetra. Among bottom-dwellers, Sterba's corydoras is an excellent choice, as unlike many corydoras species, it thrives at 28–30°C. Dwarf cichlids such as the Bolivian ram also coexist well with discus.
Completely unsuitable tankmates include: active barbs (which will nip fins), large aggressive cichlids, and any fish that prefer cooler water. Keeping discus with angelfish is controversial — although both species originate from the same region, angelfish can carry diseases to which discus are more vulnerable.
The optimal group size is 5–6 individuals or more: in a shoal, discus feel more confident and display more natural behavior.
Breeding
Breeding discus is a challenging endeavor (difficulty — 4 out of 5), but entirely achievable with proper preparation.
Discus form stable pairs, often choosing their partner from the group on their own. Spawning can be stimulated by slightly raising the temperature to 29–30°C, reducing water hardness, and providing generous feedings of live foods.
The pair selects and meticulously cleans a vertical surface — a spawning cone, broad leaf, or piece of clay pipe. The female lays up to 200–400 eggs, which both parents actively guard, fanning them with their fins to ensure water circulation.
Larvae hatch within 48–60 hours and remain attached to the substrate for the first few days. A unique feature of discus is that the fry feed on the parents' skin secretion for the first 1–2 weeks, attaching themselves to the parents' flanks. This is a critically important stage, and separating the fry from the parents during this period must be avoided.
After 2–3 weeks, the fry can be started on newly hatched brine shrimp and gradually transitioned to fine granules. Maintaining pristine water quality and feeding the fry 4–6 times daily are essential for successfully raising the young.