Discus
A large, disc-shaped cichlid needing water warmer than almost anything else in the hobby and a maintenance regime to match. Sold as the pinnacle of freshwater keeping, and genuinely demanding rather than merely expensive.
Quick profile
- Scientific name
- Symphysodon aequifasciatus
- Adult size
- 15–20 cm (5.9–7.9 in)
- Lifespan
- 10–15 years
- Temperature
- 28–31 °C (82–88 °F)
- pH
- 5.5–7.2
- Hardness
- 1–8 °dGH
- Minimum tank
- 350 L (92 US gal)
- Minimum length
- 120 cm
- Swimming zone
- Midwater
- Social
- Shoaling — at least 5
- Diet
- Carnivore
- Overall confidence
- moderate confidence
What keeping this species involves
Needs 28–31 °C, very low nitrate, soft acidic water and large frequent water changes. The temperature alone rules out most common tankmates.
Warm, very soft, acidic floodplain lakes and slow blackwater among submerged branches.
Identity and names
- Common name
- Discus
- Scientific name
- Symphysodon aequifasciatus
- Family
- Cichlidae
- Order
- Cichliformes
- Class
- Actinopterygii
Name ambiguity
The genus has been split and re-merged repeatedly. Trade names ('blue discus', 'heckel discus') do not map cleanly onto Symphysodon aequifasciatus, S. discus and S. tarzoo, and most aquarium discus are line-bred hybrids without a wild counterpart.
Adult size and growth
15–20 cm (5.9–7.9 in)
Typical lifespan in an aquarium: 10–15 years. Almost every animal sold in a shop is a juvenile, so the tank has to suit the size in the first line rather than the size in the bag.
Water and tank requirements
Deep-bodied fish reaching 20 cm, kept in groups of five or more, in a tank that must also be tall enough for the body depth.
| Requirement | Value | Notes |
|---|---|---|
| Temperature | 28–31 °C (82–88 °F) | Stability matters more than hitting an exact figure. |
| pH | 5.5–7.2 | A stable pH outside the ideal band is usually better than an unstable one inside it. |
| General hardness | 1–8 °dGH | Check your supplier's published figure before choosing species. |
| Minimum volume | 350 L (92 US gal) | A floor, not a recommendation. |
| Minimum footprint | 120 cm long × 50 cm deep | Deep-bodied fish reaching 20 cm, kept in groups of five or more, in a tank that must also be tall enough for the body depth. |
| Water flow | low | Match the outflow to this rather than to the filter's rating. |
| Lid required | Recommended | Reduces evaporation and prevents accidents. |
| Structure | Vertical wood and open swimming space; discus dislike strong current. |
Behaviour
- Timid and easily startled; sudden movement outside the tank causes bolting.
Feeding
Beef-heart mixes are traditional and heavily fouling. If used, they demand the water change schedule that goes with them.
- Diet type
- Carnivore
- Staples
- Frozen bloodworm, High-quality granules, Beef-heart preparations (with caution)
Breeding
- Strategy
- Substrate spawner; fry feed on parental skin secretions
- Difficulty
- challenging
- Parental care
- guarding
One of the very few fish whose fry feed directly on a secretion produced by both parents.
Tankmates and compatibility
Assessments are derived from stored traits by the compatibility engine, with the reasoning shown. A verdict is a statement about probability, not a guarantee — individual temperament can override it.
| Towards | Risk | What it means |
|---|---|---|
| Small fish | moderate | Anything that fits in the mouth is at risk once this species reaches adult size. |
| Adult dwarf shrimp | near-certain | Cover reduces losses but rarely prevents them where the risk is high. |
| Shrimplets | near-certain | Determines whether a shrimp colony can grow rather than merely persist. |
| Snails | low | Applies to snails you wanted as well as snails you did not. |
| Long or trailing fins | occasional | Fin damage is an entry point for secondary infection. |
| Plants | none | Tough species such as Anubias and Java fern survive most grazers. |
Assessed pairings
Any pair in the catalogue can be assessed with the compatibility checker.
Welfare considerations
Points where the way this species is commonly sold or kept differs from what it actually needs.
- The high temperature is incompatible with most community fish, including corydoras species that are commonly recommended alongside it.
- Wild-caught discus are a different proposition again and should not be a first attempt.
Problems to watch for
Most problems in a tank containing this species are general rather than species-specific. Start with the troubleshooting index and work from the observation rather than from a guess at the cause.
What AquariumHQ does not yet hold
Species-level disease susceptibility is modelled in the graph and is not yet populated. Health pages will not be published until each condition has veterinary sourcing, because health content written without evidence is the most harmful thing this product could publish. The gap is recorded in the coverage report.
Where it comes from
- Native range
- Amazon basin — Brazil, Peru, Colombia
- Habitat
- Warm, very soft, acidic floodplain lakes and slow blackwater among submerged branches.
What the checklists say
11 distribution statements retrieved from GBIF checklists. Establishment means is reproduced from the source where it states one, and left unstated where it does not — a record of presence is not a record of origin.
| Status | Places | What this means |
|---|---|---|
| Native | 3 | A checklist states the species occurs here naturally. |
| Introduced | 4 | A checklist states the species arrived here with human help. That is not a statement that it is established, harmful or illegal. |
| Recorded as present, establishment means not stated | 4 | The source records the species as present and does not say whether it is native or introduced. AquariumHQ does not fill that in. |
Evidence
Every stored value with the kind of support behind it and where to check it. Evidence type and confidence are separate axes: an editorial position held confidently and a measurement held tentatively are different things.
| Claim | Value | Evidence type | Confidence | Source |
|---|---|---|---|---|
| scientific name | Symphysodon aequifasciatus | Observed / measured | high confidence | Catalogue of Life; GBIF — Global Biodiversity Information Facility |
| native range | Amazon basin — Brazil, Peru, Colombia | Observed / measured | moderate confidence | GBIF — Global Biodiversity Information Facility |
| adult size | 15–20 cm | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| lifespan | 10–15 years | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| temperature | 28–31 °C | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| ph | 5.5–7.2 pH | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| general hardness | 1–8 °dGH | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| minimum tank volume | ≥ 350 L | AquariumHQ editorial position | moderate confidence | AquariumHQ husbandry synthesis |
| minimum tank length | ≥ 120 cm | AquariumHQ editorial position | moderate confidence | AquariumHQ husbandry synthesis |
| minimum group size | ≥ 5 | AquariumHQ editorial position | moderate confidence | AquariumHQ husbandry synthesis |
Last reviewed 2026-08-10. Values labelled as an aquarium-literature consensus are AquariumHQ editorial positions rather than measurements — see how evidence is handled.
Why we say this
What each figure on this page rests on, and how far that is from being independently established.
Every figure on this page has a provenance. Open any claim to see what AquariumHQ holds for it, which sources say what, and what a claim of that kind actually needs. Different claims need different evidence: an accepted scientific name is settled by one authority, while a legal restriction needs a current primary instrument. A single source is often the right answer rather than a thin one.
scientific nameAquariumHQ's own position, externally checkableBased on a verified authoritative source.
AquariumHQ's own position on a claim an external source could support.
What this kind of claim needs: accepted scientific name and classification — 1 authoritative source in an appropriate context. Checked against gbif on 2026-08-11. One authoritative backbone is what this class requires.
What would improve this: Go and read a source. This is reachable and has not been reached.
native rangeAquariumHQ's own position, externally checkableBased on a verified authoritative source.
AquariumHQ's own position on a claim an external source could support.
What this kind of claim needs: where the species occurs — 1 authoritative source in an appropriate context. 11 distribution statements held from GBIF checklists — native in 3, introduced in 3 countries. Establishment means is reproduced from the source, never inferred from occurrence.
What would improve this: Go and read a source. This is reachable and has not been reached.
adult sizeAquariumHQ's own position, externally checkableAquariumHQ's own position, derived from evidenced inputs.
AquariumHQ's own position on a claim an external source could support.
What this kind of claim needs: size a well-kept specimen reaches — no external source is required, provided AquariumHQ shows its reasoning. No external source is required for this class. AquariumHQ's position stands on its stated reasoning.
What would improve this: Go and read a source. This is reachable and has not been reached.
lifespanAquariumHQ's own position, externally checkableAquariumHQ's own position, derived from evidenced inputs.
AquariumHQ's own position on a claim an external source could support.
What this kind of claim needs: what aquariumhq advises for keeping — no external source is required, provided AquariumHQ shows its reasoning. No external source is required for this class. AquariumHQ's position stands on its stated reasoning.
What would improve this: Go and read a source. This is reachable and has not been reached.
temperatureIndependently verifiedConfirmed by more than one independent source.2 citations, 2 independent origins
2 citations from 2 independent origins.
- 28–30 °C — AquariumHQ husbandry synthesis · Recommended for keeping · Recommended for keeping · checked 2026-08-11
- 26–30 °C — FishBase · Tolerated range · The range the species is recorded from · checked 2026-08-11Corrected on checking from 26–31 °C.
- 26–30 °C — Ornamental Aquatic Trade Association · Recommended for keeping · Recommended for keeping · checked 2026-08-11Corrected on checking from 27–30 °C.
- 29–31 °C — UF/IFAS Extension — fish health and aquaculture publications · Conditions for breeding · Recommended for breeding
What this kind of claim needs: what aquariumhq advises for keeping — no external source is required, provided AquariumHQ shows its reasoning. 2 independent origins.
What would improve this: Nothing. Recheck when the sources are next reviewed.
phAquariumHQ's own position, externally checkableAquariumHQ's own position, derived from evidenced inputs.
AquariumHQ's own position on a claim an external source could support.
What this kind of claim needs: what aquariumhq advises for keeping — no external source is required, provided AquariumHQ shows its reasoning. No external source is required for this class. AquariumHQ's position stands on its stated reasoning.
What would improve this: Go and read a source. This is reachable and has not been reached.
general hardnessAquariumHQ's own position, externally checkableAquariumHQ's own position, derived from evidenced inputs.
AquariumHQ's own position on a claim an external source could support.
What this kind of claim needs: what aquariumhq advises for keeping — no external source is required, provided AquariumHQ shows its reasoning. No external source is required for this class. AquariumHQ's position stands on its stated reasoning.
What would improve this: Go and read a source. This is reachable and has not been reached.
minimum tank volumeOne sourceAquariumHQ's own position, derived from evidenced inputs.1 citation, 1 independent origin
A single source: oata.
- 300 L — Ornamental Aquatic Trade Association · Stated minimum · Recommended for keeping · checked 2026-08-11
What this kind of claim needs: minimum tank size — no external source is required, provided AquariumHQ shows its reasoning. No authority publishes this. AquariumHQ derives it, and the derivation is recorded with its inputs and assumptions.
What would improve this: Corroborate against a second, independent source.
minimum tank lengthAquariumHQ's judgement — no authority publishes thisAquariumHQ's own position, derived from evidenced inputs.
No external authority publishes this. The rationale carries the reasoning.
What this kind of claim needs: minimum tank size — no external source is required, provided AquariumHQ shows its reasoning. No authority publishes this. AquariumHQ derives it, and the derivation is recorded with its inputs and assumptions.
What would improve this: Keep the rationale current. There is no source to find.
minimum group sizeAquariumHQ's judgement — no authority publishes thisAquariumHQ's own position, derived from evidenced inputs.
No external authority publishes this. The rationale carries the reasoning.
What this kind of claim needs: group size — no external source is required, provided AquariumHQ shows its reasoning. No external source is required for this class. AquariumHQ's position stands on its stated reasoning.
What would improve this: Keep the rationale current. There is no source to find.
Group size and social behaviour
Strongly hierarchical. Groups of five or more spread the aggression; a group of three usually ends with one fish being harassed to death.