Discus

Symphysodon aequifasciatus

Also known as: Blue discus, Pompadour fish

Water Parameters

• Temperature: 28–30°C
• pH: 5.5–7.5
• Hardness (GH): 18–143 ppm (1–8 dGH)

Values above are general hardness (GH). For carbonate hardness (KH), the buffer that keeps pH stable, see the water parameters guide.

Care Summary

The fish most often called the king of the freshwater aquarium, and one of the most demanding to keep well. Discus are tall, disc-shaped cichlids in a dazzling range of strains (blue, red, pigeon blood, snakeskin) that have become a hobby unto themselves. The difficulty is not subtle: they need warm water around 29C, soft and slightly acidic conditions, immaculate water quality with frequent large water changes, a group for security, and a protein-rich diet, which is why they are an advanced fish rather than a beginner showpiece. Wild discus demand very soft acidic water; modern tank-bred strains are more forgiving but still unsuited to hard Australian tap water without treatment, so keepers in Brisbane, Adelaide, or Perth will need rainwater or RO blending. Given all that, a settled group of mature discus is among the most rewarding sights in the hobby. That soft, acidic water also needs a low carbonate hardness (KH), which is critical for breeding because eggs fail to fertilise or fungus in hard, high-KH water.

Tankmates

A shoaling fish that must be kept in a group of at least five, ideally six or more: a single discus or a pair develops a bullying hierarchy that stresses the weakest fish. Famously demanding tankmates because of temperature, as discus need 28 to 30C, which is too warm for most community fish and rules out cool-water species and the majority of corydoras. The proven companions are warm, soft-water species: cardinal and rummynose tetras as dithers, sterbai corydoras (one of the few cories that tolerates the heat), and german blue rams. Avoid boisterous or fin-nipping fish such as tiger barbs and serpae tetras, which harass these slow, deliberate feeders, and avoid the common pleco, which may rasp their flanks at night.

Compatible with

• Cardinal Tetra
• Rummynose Tetra
• Sterbai Corydoras
• German Blue Ram
• Bristlenose Pleco

Avoid keeping with

• Betta
• Angelfish
• Tiger Barb
• Serpae Tetra
• Common Pleco
• White Cloud Mountain Minnow
• Cherry Shrimp

Common Problems

• sensitivity to water quality requiring frequent large water changes
• bullying hierarchy in groups smaller than 5
• stress and disease from cool or unstable temperatures
• poor health in hard, alkaline water

Sources: seriouslyfish.com, fishbase.org · Last updated: 2026-06-20