Incompatible3 concerns

Bronze corydoras and Discus

Can these two share a tank? The assessment below is derived from stored behavioural and environmental traits, not from a compatibility chart.

VerdictIncompatiblemoderate confidence

Should not be attempted. At least one factor is expected to cause harm.

Minimum volume: 475 L
Minimum length: 150 cm
Factors considered: 8

Concerns

blockingtemperature

Temperature requirements do not overlap: 22–26 °C for Bronze corydoras against 28–31 °C for Discus. One animal would be kept outside its range permanently.

Derived from: environment.temperature on both records

majorpredation

Discus reaches about 20 cm and takes fish small enough to swallow. At roughly 7 cm, an adult Bronze corydoras is inside that range. This is usually discovered as fish quietly disappearing overnight rather than as visible aggression.

Derived from: traits.predation.smallFish and adultSize on both records

minorbreeding aggression

Discus becomes markedly more aggressive while spawning. A pairing that has been peaceful for months can change within a day, so plan for where the other animal goes if it does.

Derived from: traits.breedingAggression

Why it can work

pH requirements overlap at 6–7.2.
Hardness requirements overlap at 2–8 °dGH.
Bronze corydoras needs a group of at least 6. Kept in smaller numbers it is not simply lonely — shoaling species held below their threshold show chronic stress behaviour, colour loss and, in several species, increased aggression towards tankmates.
Discus needs a group of at least 5. Kept in smaller numbers it is not simply lonely — shoaling species held below their threshold show chronic stress behaviour, colour loss and, in several species, increased aggression towards tankmates.
The two occupy different levels of the tank, which reduces direct competition for space.

Conditions

Most interesting pairings are conditional on something. These are the things the keeper can actually change.

At least 6 Bronze corydoras, counted as one group
At least 5 Discus, counted as one group

Derived, or documented?

These are different claims and are shown separately. The verdict above is derived from stored traits — arithmetic on AquariumHQ's own records. Whether the pairing is actually reported to work is a separate question, and for most pairs the honest answer is that we hold nothing.

Environmental compatibility

Derived from stored traits

Temperature, pH, hardness, size and behavioural traits compared between the two records. Sound as far as it goes, and it is not evidence that the pairing works.

Behavioural evidence

Widely reported in practice

Reported consistently across aquarium practice without a single citable source. Treated as real but not as measurement.

AquariumHQ's overall position

A thermal question wearing a compatibility question's clothes. The behaviour is fine and the temperature is a genuine compromise that falls entirely on the catfish.

Factor by factor

Temperature is the whole questionReported
Discus are kept warmer than most Corydoras want. Keepers who pair them generally choose a Corydoras species selected for heat tolerance rather than assuming the genus will cope, which is itself evidence that the genus does not.
BehaviourDerived
No aggression or predation in either direction. This pairing does not fail behaviourally.

What the answer depends on. A single cell in a compatibility chart cannot hold any of these.
Depends on	How much
Tank size and dimensions	minor
Life stage	none
The individual animal	minor

How good is the overlap?

Whether two ranges intersect is a necessary condition, not evidence. What matters is WHERE the shared band sits: an overlap at the top of one animal's range and the bottom of the other's is a forced compromise however wide it looks, and it is the case a simple intersection test cannot see.

Each dimension assessed for the quality of the overlap, not merely its existence.
Dimension	Assessment	What that means here
Temperature	No overlap at all	Ranges do not meet: 22–26 against 28–31 °C.
pH	Comfortable for both	The shared band 6–7.2 pH sits centrally in both ranges, with room to drift.
Hardness	One animal at the edge of its range	The shared band 2–8 °dGH sits at the bottom of one animal's range, so that animal is permanently at its limit even though the overlap looks generous.

No overlap at all

The ranges do not meet. One animal would be kept outside its range permanently.

Factor by factor

Every factor states what it rests on. Most are derived from the traits stored on both records — sound arithmetic on AquariumHQ's own data, and not a report about how the pairing actually goes. Where a factor says 'not known', the data is missing and saying so matters, because a missing factor and a favourable one look identical once both are absent.

3 evidence-backed16 derived0 not known

Factor	Basis	Finding
Temperature	Evidence-backed	No overlap at all. Ranges do not meet: 22–26 against 28–31 °C. Reported: Discus are kept warmer than most Corydoras want. Keepers who pair them generally choose a Corydoras species selected for heat tolerance rather than assuming the genus will cope, which is itself evidence that the genus does not.
pH	Derived from stored traits	Comfortable for both. The shared band 6–7.2 pH sits centrally in both ranges, with room to drift.
Hardness	Derived from stored traits	One animal at the edge of its range. The shared band 2–8 °dGH sits at the bottom of one animal's range, so that animal is permanently at its limit even though the overlap looks generous.
Body size	Derived from stored traits	Discus reaches about 20 cm against 7 cm for Bronze corydoras — a ratio of 2.9. Size disparity drives opportunistic predation independently of temperament.
Predation	Derived from stored traits	Highest predation risk in either direction is "moderate".
Territoriality	Derived from stored traits	Strongest territoriality across the pair is "mild".
Breeding aggression	Derived from stored traits	Breeding aggression reaches "moderate". A pairing peaceful for months can change within a day of a spawn.
Fin-nipping	Derived from stored traits	No nipper-and-target combination between these two.
Aggression	Derived from stored traits	Strongest intraspecific aggression across the pair is "moderate". It bears on the pairing because a fish under pressure from its own kind redirects.
Social requirements	Derived from stored traits	Bronze corydoras needs at least 6; Discus needs at least 5. A shoaling species held below its threshold shows chronic stress and, in several species, increased aggression towards tankmates.
Group-size dependency	Derived from stored traits	The outcome depends on group size as much as on the pairing: under-grouped shoalers nip more and hide more.
Tank zone	Derived from stored traits	The two use different levels of the tank, which reduces direct competition for space.
Activity level	Derived from stored traits	Activity levels are compatible.
Food competition	Derived from stored traits	Different feeding strategies, so direct competition is limited.
Risk to shrimp and snails	Derived from stored traits	Highest risk either animal poses to dwarf shrimp or snails is "near-certain".
Effect on plants	Derived from stored traits	Neither animal damages planting.
Tank dimensions	Derived from stored traits	The more demanding of the two needs at least 350 L and 120 cm of length before anything else is in the tank. Volume alone does not describe a home for a fish that swims in straight lines.
Life stage	Evidence-backed	Life-stage dependency: none. See the documented record.
Individual variation	Evidence-backed	Individual variation: minor.

Environmental overlap

Parameter	Shared range	Reading
Temperature	No overlap	One animal would be kept outside its range.
pH	6–7.2	Stability matters more than the exact figure.
Hardness	2–8 °dGH	Check your source water before committing.

What this assessment cannot tell you

Individual temperament varies, particularly in cichlids and in bettas, and can override a favourable verdict for Bronze corydoras or Discus.
The assessment is for the pair in isolation. A third species can change the outcome in either direction.
Both animals are assessed at adult size, not at the size they are sold.
A verdict is a statement about probability, not a guarantee.

The two species

Bronze corydorasCorydoras aeneusThe most widely kept corydoras, and the one most often kept wrongly — in twos or threes, on gravel. It is a social sand-sifter that needs a group and a substrate it can push its face into.DiscusSymphysodon aequifasciatusA 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.