Last Updated: October 17, 2026
- Discus Quick Facts
- Why Discus Are Demanding
- Tank Size and Group Size
- Water Parameters
- Water Change Routine
- Setup and Filtration
- Feeding
- Tank Mates
- Common Diseases and Troubleshooting
- Weekly Routine for a Discus Tank
- Buying Healthy Discus
- Who Should and Should Not Keep Discus
- Common Mistakes
- Frequently Asked Questions
Discus (Symphysodon) are demanding cichlids that need warm water of about 28 to 30 C, soft to moderately soft, slightly acidic to neutral water, a tank of roughly 75 gallons (about 285 litres) for a group of five or six (sources range from about 50 to 75 gallons), and very frequent large water changes. They are not beginner fish, because they foul water quickly, are sensitive to stress and disease, and are slow to recover from neglect. Keepers who can commit to a weekly or even daily routine, though, find them calm, sociable and rewarding.
Quick answer: Our top pick in 2026 is the Adult size — our #1 rated choice. See the full ranked comparison, alternatives and buying advice below.
Discus Quick Facts
| Trait | Detail |
|---|---|
| Adult size | Commonly quoted at 15 to 20 cm (6 to 8 in) body diameter; Seriously Fish gives about 14 cm standard length for wild Symphysodon aequifasciatus |
| Minimum tank | Sources range from about 50 to 75 gallons for a small group; Seriously Fish lists 120 x 45 x 45 cm (about 255 L) as the minimum for juveniles or a pair; tall tanks of 45 to 50 cm are preferred |
| Group size | Five or six at minimum; discus are social |
| Temperature | Mostly 28 to 30 C; Seriously Fish lists 26 to 30 C and some guides allow up to about 32 C |
| pH / hardness | pH about 6.0 to 7.0 for most captive-bred strains; softer and more acidic for wild fish (wild Symphysodon discus can live in water with pH near 4 to 5); Seriously Fish lists 0 to 5 dGH for wild fish, and many guides give roughly 1 to 8 dGH |
| Diet | Omnivore: beef-heart blends, quality pellets, frozen bloodworm and brine shrimp; high-protein foods |
| Lifespan | Sources vary: about 8 to 15 years, with 10 years or so commonly quoted |
| Temperament | Peaceful, shy, sometimes bossy in groups at spawning |
| Care level | Advanced |
Why Discus Are Demanding
Discus come from the rivers of northern South America, where water is warm, soft and very low in minerals. Domesticated strains are more tolerant than wild-caught fish, but the same needs shape the hobby:
Brightwell Aquatics DiscusCode Discus Fish Trace Supplement, 500ml
Included for 'Discus Water Parameters, Diet and Tank Mates: A Complete Care Guide' because the listing specifies 500ml, details this guide uses to compare options.
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Hikari® Discus Bio-Gold® Sinking Protein-Packed Discs for Discus and Tropical Fish, 2.82 oz (80g)
Included for 'Discus Water Parameters, Diet and Tank Mates: A Complete Care Guide' because the listing specifies 2.82 oz (80g), details this guide uses to compare options.
View on Amazon
Seachem NutriDiet Discus Flakes - Fortified Ornamental Fish Food Supplement 500g
Included for 'Discus Water Parameters, Diet and Tank Mates: A Complete Care Guide' because the listing specifies Fortified Ornamental Fish Food Supplement 500g, details this guide uses to compare options.
View on Amazon
Hikari® Vibra Bites® Slow-Sinking Color-Enhancing Sticks for Tropical Fish, 9.8 oz (280g)
Included for 'Discus Water Parameters, Diet and Tank Mates: A Complete Care Guide' because the listing specifies 9.8 oz (280g), details this guide uses to compare options.
View on Amazon- Heavy feeders, high waste: juveniles in particular eat several times a day, producing a lot of ammonia and nitrate.
- Heat: 28 to 30 C speeds up the growth of bacteria and parasites, so any lapse in cleanliness has consequences.
- Stress sensitivity: flashing lights, aggressive tank mates, sudden changes and poor water cause hiding, dark colour and loss of appetite.
- Slow growth: a juvenile takes a year or more to become an adult, and stunting from poor early care is common.
Because of that, discus are best seen as a project fish rather than an impulse buy.
Tank Size and Group Size
Seriously Fish and other sources agree on keeping discus in groups, and sources commonly give a minimum between 50 and 75 gallons for a small group, with taller tanks preferred. Discus are tall, flat-bodied fish, so a tank with a height of at least 45 cm gives them room to move without bumping the surface or floor.
A simple stocking calculation
- Adult body diameter is about 15 to 20 cm. As a rough rule of thumb, allow about 40 to 50 litres of well-filtered water per adult in a bare, tall setup.
- Five or six adults therefore point to about 250 to 300 litres, matching the 75-gallon advice.
- A pair needs less volume, but a lone discus is often shy and stressed, so pairs and groups are the norm.
- If you add tank mates, add volume rather than squeezing in more fish. Surface area and footprint support oxygen exchange and give subordinate discus space to avoid dominant ones.
- Juveniles can start in smaller tanks, but they need frequent water changes and should move into their adult tank as they grow.
Keepers often argue about group size. Too few fish allow a bully to single out one individual; too many in a small tank raise waste and aggression. A group of six in a large tank is a practical middle. Seriously Fish describes wild discus as shy, skittish fish that should be kept in groups.
Water Parameters
- Temperature: mostly 28 to 30 C (Seriously Fish lists 26 to 30 C); juveniles and sick fish may benefit from slightly warmer water during treatment.
- pH: captive-bred discus often adapt to 6.0 to 7.0. Wild fish do better in softer, more acidic water, and some sources list pH near 6.0 to 6.5 as the target for sensitive fish, while Seriously Fish gives 5.0 to 7.0.
- Hardness: soft; Seriously Fish lists 0 to 5 dGH and many guides accept up to about 8 dGH.
- Ammonia and nitrite: zero.
- Nitrate: as low as practical; many keepers aim under 10 to 20 mg/L through water changes.
Temperature and pH stability matter more than chasing exact numbers. Large swings between water changes cause stress. Match temperature and, if possible, hardness in new water before adding it. If tap water is hard, some keepers use reverse osmosis water mixed with tap, but this requires care so that minerals remain at a safe level.
Water Change Routine
Water changes are the main tool for keeping discus healthy. Common routines among keepers:
| Setup | Water change | Notes |
|---|---|---|
| Juvenile growing tank, heavy feeding | 30 to 50 percent daily or every other day | Supports growth and removes waste |
| Adult group, lightly planted | 30 to 50 percent two or three times a week | Keeps nitrate low |
| Adult group, bare bottom | 50 percent several times a week | Easy to siphon waste daily |
| Heavily planted, low feeding | 25 to 30 percent weekly may be enough, with testing | Only if nitrate stays low |
Always dechlorinate the new water and match the temperature. Siphon uneaten food before it breaks down.
Setup and Filtration
- Substrate: many keepers use a bare bottom for easy cleaning. Fine sand is also used.
- Filtration: a large sponge filter or canister system with strong biological capacity and gentle flow. Discus dislike strong currents.
- Lighting: dim, soft light; floating plants provide shade.
- Decor: smooth driftwood, tall plants or sword plants, and a few visual barriers. Avoid sharp edges.
- Heater: use a reliable thermostat-controlled heater and a separate thermometer.
- Lid: a cover keeps the warm air in and prevents jumps.
Feeding
Discus are omnivores with a high-protein diet in the wild. Common practice is a mix of foods fed in small portions, two to three times daily for adults and up to four times for juveniles.
- High-quality discus pellets or granules as a base.
- Frozen foods: bloodworm, brine shrimp, mysis. Bloodworm should not be the only item.
- Beef-heart mixes are traditional, but they are rich and can foul water if overfed.
- Some keepers add vegetable matter such as spirulina.
- Feed only what is eaten in a few minutes and remove leftovers.
Shy discus may refuse food at first. Quiet surroundings and compatible tank mates help them settle.
Tank Mates
Discus are slow and peaceful, and they prefer warm water. Tank mates should enjoy the same temperature and be gentle, with no fin nipping.
| Group | Examples | Notes |
|---|---|---|
| Good | Cardinal tetras, rummynose tetras, harlequin rasboras, Corydoras that tolerate heat (such as sterbai), clown loaches in large tanks, bristlenose plecos | Peaceful, warm-water, non-nippers |
| Risky | Angelfish, which may carry disease and compete for space; larger gouramis; fast tetras that nip | Possible stress, competition and shared disease risk |
| Avoid | Barbs such as tiger barbs, aggressive cichlids, goldfish, cool-water fish like white cloud minnows | Nipping, bullying and temperature mismatch |
Many keepers stock discus alone in a species tank to reduce disease risk and simplify water changes.
Common Diseases and Troubleshooting
| Symptom | Likely cause | Fix |
|---|---|---|
| Dark colour, hiding, not eating | Stress, bullying, poor water | Test water, increase water changes, reduce disturbance, check tank mates |
| Stringy white faeces, weight loss | Internal parasites such as hexamita (often called hole in the head) | Improve water quality and diet; consult an aquatic vet or use a recommended treatment |
| Pits or holes on head | Chronic poor water, nutritional problems, hexamita | Frequent water changes, varied diet, treatment as advised |
| Clamped fins, rapid gills | Gill flukes, bacterial infection, poor oxygen | Water change, oxygenation, treat after diagnosis |
| White spots | Ich | Raise temperature carefully if tolerated and use an ich medication; follow label instructions |
| Cloudy slime coat | Skin flukes or poor water | Water quality first; targeted treatment |
New fish should be quarantined for several weeks before going into the main tank. This is one of the most effective ways to avoid long-term disease.
Weekly Routine for a Discus Tank
- Daily: feed two to three small meals, siphon leftovers, check temperature and watch every fish for appetite, colour and breathing.
- Two or three times a week: change 30 to 50 percent of the water with dechlorinated, temperature-matched water.
- Weekly: test ammonia, nitrite, nitrate and pH; wipe the glass; trim plants.
- Monthly: rinse filter media in used tank water, never tap water, and check heater, thermometer and airline tubing.
Buying Healthy Discus
Start with healthy stock from a source that keeps discus in clean, warm water. Alert fish with full bodies, clear eyes, smooth skin, firm dark faeces and an eager response to food are good signs. Avoid fish with pinched bellies, stringy white faeces, dark colour, ragged fins or a habit of hiding in a corner. Young discus of about 7 to 10 cm are often easier to acclimatise and let the group grow up together, though they need more feeding and water changes than adults. Wild-caught fish are generally described as more sensitive to water chemistry and parasites, so captive-bred strains are the usual choice for most home aquariums.
Quarantine for at least three to four weeks in a bare tank with a sponge filter, a heater and daily water changes. Observe appetite and droppings before adding the new fish to the main group.
Who Should and Should Not Keep Discus
| Pick discus if… | Skip discus if… |
|---|---|
| You have an established, stable tank of 75 gallons or more | You are new to fishkeeping and still learning to cycle a tank |
| You can do large water changes several times a week | You travel often and cannot change water or feed on schedule |
| You can keep a heater-controlled tank at 28 to 30 C | Your tank has aggressive or cool-water fish you want to keep |
| You want a calm showpiece fish and accept a slow start | You want a low-maintenance community tank |
Common Mistakes
- Buying too few discus, or one alone.
- Too-small tanks or very short tanks.
- Insufficient water changes.
- Mixing with fin nippers or cool-water fish.
- Skipping quarantine.
- Overfeeding rich beef-heart mixes and letting waste build up.
- Letting the temperature drift.
Frequently Asked Questions
What temperature do discus need?
Most discus do best at about 28 to 30 C, and sources vary slightly (Seriously Fish lists 26 to 30 C). A reliable heater and thermometer are important.
How many discus should be kept together?
At least five or six, in a tank of roughly 75 gallons or more (sources range from about 50 gallons). Groups spread aggression and make fish more confident.
Can beginners keep discus?
It is usually discouraged. Discus need stable water, frequent water changes and attention to disease. Starting with an easier fish and moving up with experience is wiser.
How often should I change discus water?
Many keepers change 30 to 50 percent two or three times a week, and juveniles may need daily changes. Heavily planted tanks may need less, but testing nitrate is the best guide.
What do discus eat?
They eat high-protein foods such as discus pellets, frozen bloodworm, brine shrimp and beef-heart blends. Feed small portions several times a day and remove leftovers.
Which tank mates are safe for discus?
Cardinal tetras, rummynose tetras, heat-tolerant Corydoras and peaceful plecos are common choices. Avoid fin nippers and cool-water fish.
How long do discus live?
Sources vary from about 8 to 15 years, with around 10 years commonly quoted for fish in good conditions. Stress and poor water shorten their lives.
Ready to decide? Our #1 pick for 2026 is the Adult size.
Live price & availability on Amazon.
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