Discus Learning Center

Discus care guide

Everything you need to keep discus healthy and happy, in one place: choosing fish, setting up the aquarium, water quality, feeding, tankmates, health, breeding and the remarkable history of the King of the Aquarium.
On this page

Getting started · Tank setup · Water quality · Feeding · Tankmates · Health & disease · Breeding · Varieties · History & science

Chapter 1

Getting started with discus

Discus have a reputation for being difficult, but most problems come from a handful of avoidable mistakes. Prepare properly and you will be rewarded with calm, colourful fish that can live for more than a decade.
Before you buy
  • Cycle the aquarium fully first. Ammonia and nitrite must both read zero, which usually takes four to six weeks in a new tank.
  • Plan for a group of at least five or six discus and a tank of 200 litres (55 US gallons) or more.
  • Choose tank-raised fish from a reputable breeder. They adapt far better than wild-caught discus.
  • Buy juveniles of at least 7–8 cm (3 in). Smaller fish need intensive feeding and very frequent water changes to grow properly.
  • Buy the whole group from one source at the same time to reduce the risk of disease.
  • Set up a small quarantine tank for newcomers and emergencies.
How to spot a healthy discus
  • A full, round body with no sunken belly or pinched forehead.
  • Eyes in proportion to the body. A large eye on a small body can be a sign of stunted growth.
  • Upright, intact fins and smooth skin without pits, spots or excess slime.
  • Eager feeding and calm, confident swimming near the front of the tank.
  • Even colour. Some darkening after transport is normal, but fish that stay dark and hide may be stressed or ill.
  • Dark, firm droppings. White, stringy droppings can point to internal parasites.
The golden rule: consistency

Discus are rarely harmed by one parameter being slightly off target. They are harmed by sudden change. A steady routine of feeding, water changes and maintenance is the secret most experienced keepers share.

Chapter 2

Setting up a discus aquarium

Discus are tall, sensitive fish that appreciate calm and stability. A well-planned tank makes every other part of their care easier.
Tank size and shape

Allow roughly 40 litres (10 US gallons) per adult, with a minimum of about 200 litres (55 US gallons) for a group of five or six. Because discus are tall-bodied, choose a tank at least 45–50 cm (18–20 in) high.
Filtration

Discus need strong biological filtration but gentle water flow. Canister filters and air-driven sponge filters are both popular. Avoid powerful currents that force discus to swim constantly.
Heating

Keep the water at 28–30 °C (82–86 °F). Use a reliable heater, or two smaller ones for safety, and check the temperature every day with a separate thermometer.
Lighting

Moderate light is best. Floating plants or shaded areas help shy fish feel secure, and a regular day–night cycle of around 8–10 hours keeps them settled.
Substrate and décor

Bare-bottom tanks are the easiest to keep spotless and are ideal for young fish. In display tanks, use a thin layer of fine sand with driftwood and roots that recreate the flooded forest.
Plants

Choose plants that tolerate warm water, such as Amazon swords, Anubias, Java fern and Cryptocoryne. Leave open swimming space at the front of the tank.
Where to put the tank

Choose a quiet room away from doors, loudspeakers and heavy foot traffic. Sudden movement outside the glass can startle discus and send them crashing into the décor. Make sure the stand can take the full weight of the filled aquarium.

Chapter 3

Water quality and parameters

Clean, warm, soft water is the foundation of discus keeping. Most health problems can be traced back to water quality, so this is where to focus your effort.
ParameterTargetNotes
Temperature28–30 °C (82–86 °F)Up to 31 °C for young fish, breeding pairs or during treatment
pH6.0–7.0Tank-raised discus adapt to slightly higher values; keep it stable
General hardness (GH)1–8 dGHSofter water is needed for eggs to hatch
Carbonate hardness (KH)1–4 dKHVery low KH lets pH drop quickly, so test regularly
Ammonia0 ppmAny reading points to a filtration or overfeeding problem
Nitrite0 ppmToxic even at low levels
NitrateBelow 20 ppmIdeally under 10 ppm; kept low by water changes
Total dissolved solids (TDS)Below about 200 ppmBreeders often aim much lower, under 100 ppm
Water changes

This is the single most important habit. Change 30–50% of the water at least once a week for adults, and daily or every other day for growing juveniles. Match the temperature of new water to within about 1 °C and always use a dechlorinator.
Stability over perfection

Sudden swings in temperature, pH or hardness stress discus far more than a stable value that is slightly off target. Avoid chasing numbers with chemicals. If your tap water is very hard, blend it with reverse osmosis (RO) water instead.
Testing

Keep a liquid test kit for ammonia, nitrite, nitrate and pH, plus an inexpensive TDS meter. Test new tanks often, and established tanks weekly or whenever your fish behave unusually.
The nitrogen cycle, explained

Fish waste and leftover food release ammonia, which is toxic. Beneficial bacteria in the filter turn ammonia into nitrite (also toxic) and then into nitrate, which is far less harmful and is removed with water changes. A new tank needs several weeks for these bacteria to grow. This process is called cycling.

Chapter 4

Feeding discus

In the wild, discus pick at insect larvae, small crustaceans, algae, plant matter and detritus among submerged roots. In the aquarium they do best on a varied, protein-rich diet served in small portions.
Good foods
  • High-quality discus granules or pellets as the staple
  • Frozen bloodworms, brine shrimp and mysis shrimp
  • Blackworms, frozen or live from a clean, trusted source
  • Homemade beef heart or seafood mixes: a traditional food for growing fish, but rich, so feed in moderation
  • Occasional spirulina or vegetable-based foods for variety
How often to feed
  • Juveniles: 3–5 small meals a day. Their growth depends on it.
  • Adults: 2–3 meals a day.
  • Offer only what is eaten within a few minutes.
  • Remove leftovers promptly. In warm water, uneaten food pollutes the tank quickly.
  • A healthy adult can skip a day now and then, but a discus that refuses food for several days needs attention.
Tips for picky eaters

Discus are creatures of habit. Feed at the same times and in the same spot, dim the lights if fish are nervous, and introduce new foods gradually alongside familiar ones. New arrivals often need a few days before they eat confidently.

Chapter 5

Choosing tankmates

Discus are peaceful and easily intimidated, so companions must be calm, comfortable at 28–30 °C and never compete aggressively for food. A discus-only aquarium is perfectly fine, and often the easiest option.
Good companions
  • Cardinal tetras (Paracheirodon axelrodi)
  • Rummy-nose tetras (Hemigrammus bleheri)
  • Sterbai cory catfish (Corydoras sterbai)
  • Bristlenose plecos (Ancistrus)
  • German blue rams (Mikrogeophagus ramirezi)
  • Marbled hatchetfish (Carnegiella strigata)
Fish to avoid
  • Fin-nippers such as tiger barbs and serpae tetras
  • Boisterous or aggressive cichlids
  • Fast, greedy eaters that outcompete discus at mealtimes
  • Cool-water species such as goldfish, neon tetras and many cory catfish
  • Fish that latch onto a discus’s slime coat, such as Chinese algae eaters and common plecos
  • Angelfish are sometimes kept with discus, but they can be pushy at feeding time and may bring in disease, so approach with caution

Remember: quarantine every new fish, including tankmates, before it joins your discus.

Chapter 6

Health and common diseases

Most discus illnesses begin with stress: poor water quality, sudden changes, bullying or new fish that were not quarantined. Learn the warning signs so you can act early.
Warning signs
  • Staying very dark or hiding for long periods
  • Clamped fins held tight against the body
  • Refusing food for more than a day or two
  • White, stringy or clear droppings
  • Rapid breathing, breathing with one gill or hanging near the surface
  • Rubbing against décor or the substrate
  • Cloudy eyes, white spots, excess slime, pits on the head or ragged fins
What to do first
  1. Test the water: ammonia, nitrite, nitrate, pH and temperature.
  2. If anything is off, do a water change, matching the temperature carefully.
  3. Watch closely and write down every symptom.
  4. Move affected fish to a hospital tank if you can.
  5. Ask an aquatic vet or experienced breeder before medicating, and follow dosing instructions exactly.

Common conditions

Gill flukes

Tiny parasitic worms that attach to the gills. Look for rapid breathing, one gill held closed, scratching against décor and darkening. Treatment usually involves a praziquantel-based medication.
Internal flagellates (Hexamita / Spironucleus)

Intestinal parasites that often take hold when fish are stressed. Signs include white, stringy droppings, loss of appetite, dark colour and weight loss. They are commonly treated with metronidazole under guidance.
Hole-in-the-head (HITH)

Small pits or erosion around the head and along the lateral line. It is linked to poor water quality, poor diet and internal flagellates. Improve water and nutrition and treat any underlying parasites.
White spot (ich)

Small, salt-like white spots on the body and fins, often with scratching. Treat promptly with a suitable medication, and follow the instructions carefully because discus are sensitive.
Bacterial infections

Fin rot, cloudy eyes and ulcers usually follow stress or poor water quality. Fix the cause first. Severe cases may need antibacterial treatment.
Discus plague

A highly contagious illness, thought to be viral, that causes heavy slime, darkening and fin damage. It is most often introduced by adding new fish without quarantine.

This guide is general information, not veterinary advice. Always confirm a diagnosis and treatment with a qualified aquatic vet or an experienced keeper.

Chapter 7

Breeding discus

Discus are devoted parents: male and female guard the eggs together and feed their young from their own skin. Breeding them is a challenge, but a hugely rewarding one.
Forming pairs

The easiest way to get a pair is to raise a group of six or more young discus together and let pairs form naturally. A pair will claim a spot, clean it and defend it. Discus usually mature at around 12–18 months.
Males and females

Discus are hard to sex by appearance. Males are often larger, with thicker lips and a more pointed dorsal fin. The only reliable sign is the breeding tube at spawning time: blunt and wide in females, narrow and pointed in males.
The breeding tank

Use a quiet tank of at least 100–120 litres (25–30 US gallons) with a sponge filter and a vertical spawning surface such as a breeding cone. Keep the water soft, low in dissolved solids and around 29–30 °C. Hard water can stop eggs from hatching.

From egg to free-swimming fry

Day 0 · Spawning

The female lays rows of eggs, often 100–300, on a vertical surface and the male fertilises them. Both parents fan and guard the clutch.
Days 2–3 · Hatching

The eggs hatch into wrigglers that stay attached to the spawning site. The parents may move them to a new spot.
Days 5–6 · Free-swimming

The fry start to swim and head straight for their parents’ sides to feed.
Weeks 1–2 · Discus milk

The fry feed on a nourishing mucus from the parents’ skin. Newly hatched brine shrimp can be added after about a week.
Weeks 3–5 · Independence

Once the fry eat brine shrimp well, move them to their own tank with frequent feeding and water changes.

Common setbacks: new pairs often eat their first few clutches, which usually improves with experience. Unfertilised eggs turn white within a day. Keep the room quiet and avoid disturbing the parents.

Chapter 8

Discus varieties

All discus belong to the genus Symphysodon, but colour and pattern vary enormously. Wild forms are named after their appearance and origin, while captive-bred strains are the result of decades of selective breeding.

Wild types

Heckel

Symphysodon discus

The first discus described, in 1840. Recognised by its bold, dark central bar. Found mainly in the Rio Negro region and prefers very soft, acidic water.
Green

Wild type

An olive-to-green body with teal markings on the head and fins. The famous Tefé green often has red spots on the lower body.
Blue

Wild type

A brown-to-purple body with more extensive blue striations than the brown form, especially on the head and fins.
Brown

Wild type

The most common wild form: warm brown to reddish, with blue lines mostly on the head and fins.

Captive-bred strains

Turquoise

Captive-bred

Dense turquoise-blue lines over a red-brown body. Developed by pioneering breeders such as Eduard Schmidt-Focke and Jack Wattley, and a foundation of many modern strains.
Blue Diamond

Captive-bred

A solid, glossy blue body with no pattern at all, one of the most striking solid-colour strains.
Pigeon Blood

Captive-bred

A pale cream-to-orange body laced with fine red-orange lines. Developed in Thailand in the early 1990s; often shows black speckles known as peppering.
Red Melon

Captive-bred

A bold, even red-to-orange body. Developed from Pigeon Blood lines, with the best colour on a good diet.
Snakeskin

Captive-bred

Very fine, densely packed lines that resemble snake scales, often with more than the usual nine bars.
Leopard

Captive-bred

Red dots and spots scattered over a blue-green base, like the markings of a leopard.
Golden

Captive-bred

A warm yellow-to-gold body with reduced dark markings, a striking contrast to the classic blues and reds.
Albino

Captive-bred

Lacks dark pigment, giving a pale body and fins. Albino forms exist of many strains, from albino golden to albino red.
Colour tells you about mood

Discus darken and show their vertical bars when they are frightened, ill or guarding young, and brighten when they are settled and healthy. Colour also deepens with age and a good diet, so young fish rarely show their full potential.

Chapter 9

History and science

From the flooded forests of the Amazon to aquariums around the world, the story of the discus is as remarkable as the fish itself.
Where discus live

Discus live in slow-moving tributaries, lakes and flooded forests of the Amazon basin. Water levels there rise and fall by several metres each year. In the flood season discus spread out into the drowned forest; in the dry season they gather in groups along the banks among fallen trees and roots. Their water ranges from tea-coloured blackwater, like the Rio Negro, to clearer rivers, and is almost always warm, soft and acidic.
Built for the flooded forest

A tall, flat body lets discus slip between branches and turn on the spot, while long dorsal and anal fins give them precise, hovering control. Their nine vertical bars, one running through the eye, break up their outline in the dappled light, and can be switched on and off to signal mood.

A short timeline

1840

Austrian naturalist Johann Jakob Heckel describes the first discus, Symphysodon discus.

1904

French ichthyologist Jacques Pellegrin describes Symphysodon aequifasciatus, the discus behind most aquarium varieties.

1950s

Scientists document how discus parents feed their fry with mucus from their skin, behaviour that is extremely rare among fish.

Mid-1900s

Breeders such as Eduard Schmidt-Focke in Germany and Jack Wattley in the United States develop turquoise strains and learn to raise discus reliably.

1990s

Breeders in Southeast Asia create new colour forms such as Pigeon Blood, and discus become widely available around the world.

Today

Most aquarium discus are captive-bred. Scientists still debate how many species exist, with between two and four recognised depending on the study.

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