Moonlight gourami and Red zebra cichlid
Can these two share a tank? The assessment below is derived from stored behavioural and environmental traits, not from a compatibility chart.
Workable only in unusual circumstances. Not a pairing to plan around.
- Minimum volume
- 375 L
- Minimum length
- 165 cm
- Factors considered
- 11
Concerns
Reported pH ranges do not overlap: 6–7.5 against 7.6–8.6. Chasing a compromise pH with additives is less stable than keeping each animal in water that suits it.
Derived from: environment.ph on both records
Red zebra cichlid harasses slow-moving or long-finned tankmates, and Moonlight gourami fits that description. Persistent harassment shows up as hiding, clamped fins and refusal to feed long before it shows up as injury.
Derived from: traits.predation.harassment and traits on the second record
Red zebra cichlid 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
Red zebra cichlid is a boisterous, fast-moving fish and Moonlight gourami is a slow, deliberate one. The slower animal typically loses out at feeding time and spends more time hiding, neither of which is obvious from a quick look at the tank.
Derived from: traits.activity on both records
Moonlight gourami defends a territory and both animals use the same part of the tank, so give the territory-holder a defensible area away from the main swimming space.
Derived from: traits.territoriality and zone on both records
Moonlight gourami 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
Flow preferences differ (still against moderate). Aim for the middle and provide a sheltered corner.
Derived from: traits.flowPreference on both records
Why it can work
- Temperature requirements overlap comfortably at 24–28 °C, with room for both animals to sit inside their preferred range.
- Hardness requirements overlap at 10–18 °dGH.
- Red zebra cichlid 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 5 Red zebra cichlid, counted as one group
- At least 375 L with a footprint of 165 cm or more, before counting anything else in the tank
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
No behavioural evidence held
AquariumHQ holds no behavioural evidence for this pairing. The verdict is derived entirely from stored traits — it is arithmetic on our own records, not a report about how the pairing actually goes.
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.
| Dimension | Assessment | What that means here |
|---|---|---|
| Temperature | Comfortable for both | The shared band 24–28 °C sits centrally in both ranges, with room to drift. |
| pH | No overlap at all | Ranges do not meet: 6–7.5 against 7.6–8.6 pH. |
| Hardness | Workable | The shared band 10–18 °dGH is usable, though it does not sit centrally for both animals. |
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.
| Factor | Basis | Finding |
|---|---|---|
| Temperature | Derived from stored traits | Comfortable for both. The shared band 24–28 °C sits centrally in both ranges, with room to drift. |
| pH | Derived from stored traits | No overlap at all. Ranges do not meet: 6–7.5 against 7.6–8.6 pH. |
| Hardness | Derived from stored traits | Workable. The shared band 10–18 °dGH is usable, though it does not sit centrally for both animals. |
| Body size | Derived from stored traits | Adult sizes are comparable at about 18 cm and 13 cm, so neither is a mouthful for the other. |
| Predation | Derived from stored traits | Highest predation risk in either direction is "high". |
| Territoriality | Derived from stored traits | Strongest territoriality across the pair is "strong". |
| Breeding aggression | Derived from stored traits | Breeding aggression reaches "strong". 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 "strong". It bears on the pairing because a fish under pressure from its own kind redirects. |
| Social requirements | Derived from stored traits | Red zebra cichlid 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 | One animal is boisterous and the other sedate. The slower one typically loses out at feeding time and hides more, neither of which is obvious from a quick look at the tank. |
| 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 | Red zebra cichlid eats plants, which constrains the aquascape rather than the pairing. |
| Tank dimensions | Derived from stored traits | The more demanding of the two needs at least 250 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 | Not known | AquariumHQ holds no record of whether this pairing changes as either animal matures. Stored traits describe adults, so a pairing that fails at adult size looks identical to one that never fails. |
| Individual variation | Not known | AquariumHQ holds no record of how much this pairing varies between individuals. For several species — bettas and cichlids especially — that variation decides the outcome and a species-level verdict cannot express it. |
Environmental overlap
| Parameter | Shared range | Reading |
|---|---|---|
| Temperature | 24–28 °C | Aim for the middle of the shared band. |
| pH | No overlap | Chasing a compromise pH is less stable than keeping each animal separately. |
| Hardness | 10–18 °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 Moonlight gourami or Red zebra cichlid.
- 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.
Where the two water bands meet
Derived from the ranges AquariumHQ publishes for each species. The compatibility engine reads the same numbers; this is what they look like drawn on one axis.
Temperature (°C)
Scale: 0 to 36 °C.
pH (pH)
Scale: 4 to 9.5 pH.
No overlap. There is no ph at which both species are inside their advised range.
Hardness (°dGH)
Scale: 0 to 30 °dGH.
Why the bands sit where they do
The overlap above is arithmetic. This is where the two numbers came from — the kind of water each animal is recorded from, and how much room that leaves.
These two animals come from different kinds of water, and that is where the arithmetic below comes from rather than from anything about their temperaments.
Moonlight gourami
Lowland floodplain
40–300 µS/cm · still flow · low oxygen
Red zebra cichlid
Lake Malawi
200–280 µS/cm · low flow · near saturation oxygen
- TemperatureMoonlight gourami 24–30°CRed zebra cichlid 24–28°C
Both inside their range from 24–28°C — 100% of the narrower animal’s range.
A wide window. Both animals are inside their own range across most of it, and the tank can be run without either sitting at an edge.
- pHMoonlight gourami 6–7.5Red zebra cichlid 7.6–8.6
No overlap.
No overlap at all. There is no temperature, pH or hardness that suits both.
- General hardnessMoonlight gourami 2–18 dGHRed zebra cichlid 10–20 dGH
Both inside their range from 10–18 dGH — 80% of the narrower animal’s range.
A wide window. Both animals are inside their own range across most of it, and the tank can be run without either sitting at an edge.
Computed from the ranges AquariumHQ publishes for each species, each of which records what it rests on — a source value, a habitat inference, a physiological requirement or a trade convention. Most are habitat inferences, and the species pages say which.