Blue moorii
A shallow-water algae grazer kept in large single-species colonies because anything smaller ends in one fish killing the rest. It is the most demanding common Tanganyikan in the hobby and almost all of the difficulty is social and dietary rather than chemical.
Quick profile
- Scientific name
- Tropheus moorii
- Adult size
- 11–14 cm (4.3–5.5 in)
- Lifespan
- 8–12 years
- Temperature
- 24–27 °C (75–81 °F)
- pH
- 8–9
- Hardness
- 12–22 °dGH
- Minimum tank
- 450 L (119 US gal)
- Minimum length
- 150 cm
- Swimming zone
- All levels
- Social
- Colony — at least 12
- Diet
- Herbivore
- Overall confidence
- moderate confidence
What keeping this species involves
A twelve-fish minimum group, a strictly vegetable diet, very hard alkaline water and a tank long enough to hold the colony. Each requirement is manageable alone and the combination is a project rather than an addition.
The upper few metres of the rocky shore, in bright light and surge, grazing algal turf from wave-washed rock.
Identity and names
- Common name
- Blue moorii
- Scientific name
- Tropheus moorii
- Family
- Cichlidae
- Order
- Cichliformes
- Class
- Actinopterygii
- Also sold as
- Tropheus moorii, Tropheus, blunthead cichlid, Kasanga tropheus
Name ambiguity
Tropheus moorii as the trade uses it covers a large number of geographically separated colour populations around Lake Tanganyika, several of which may prove to be distinct species. The name on a shop tank is usually a locality name rather than a determination, and mixing localities is what most damages the group.
Adult size and growth
11–14 cm (4.3–5.5 in)
Typical lifespan in an aquarium: 8–12 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.
Shape, which is what the compatibility engine reads instead of length alone: deep-bodied with a moderate. Assigned from what is typical of Cichlidae, not examined for this species.
Water and tank requirements
A colony species where the requirement is a group of a dozen or more adults, and the tank has to hold that group rather than the individual fish.
Temperature (°C)
Scale: 0 to 36 °C.
pH (pH)
Scale: 4 to 9.5 pH.
Hardness (°dGH)
Scale: 0 to 30 °dGH.
Why these ranges: Lake Tanganyika is harder and more alkaline than Malawi, and stable to a degree few natural waters are. The upper pH here is the lake's own and is not a target to chase with additives.
Where these figures come from
Habitat class
Lake Tanganyika
An ancient, enormous, strongly buffered rift lake with the most alkaline water any commonly kept aquarium fish comes from.
Not interchangeable with Malawi. Tanganyika is markedly more alkaline and more mineral-rich, and its temperature is markedly more stable, because the lake is deep enough to be its own thermostat.
- Conductivity
- 570–700 µS/cm
- Flow
- low
- Dissolved oxygen
- near saturation
- Seasonality
- weak
These are figures for the KIND of water body, not measurements of this species. They are AquariumHQ’s summary of the general limnology and are given wide because the water is.
- TemperatureReasoned on this record
- This record states its own reason for this band. See the water section.
- pHReasoned on this record
- This record states its own reason for this band. See the water section.
- General hardnessReasoned on this record
- This record states its own reason for this band. See the water section.
| Requirement | Value | Notes |
|---|---|---|
| Temperature | 24–27 °C (75–81 °F) | Stability matters more than hitting an exact figure. |
| pH | 8–9 | A stable pH outside the ideal band is usually better than an unstable one inside it. |
| General hardness | 12–22 °dGH | Check your supplier's published figure before choosing species. |
| Carbonate hardness | 14–20 °dKH | Buffering capacity — what stops the pH moving. |
| Minimum volume | 450 L (119 US gal) | A floor, not a recommendation. |
| Minimum footprint | 150 cm long × 50 cm deep | A colony species where the requirement is a group of a dozen or more adults, and the tank has to hold that group rather than the individual fish. |
| Water flow | high | Match the outflow to this rather than to the filter's rating. |
| Lid required | Recommended | Reduces evaporation and prevents accidents. |
| Structure | Rock rubble across the back and sides with open swimming space in front. Strong flow and high oxygen reproduce the wave-washed shore this fish lives on. |
Behaviour
- Grazes rock in short bursts through the whole day and rarely holds still, which is why the colony reads as constant motion.
- Established colonies settle into a visible order, and a fish removed and returned a day later re-enters at the bottom of it.
Telling males from females
Almost none that is readable. Males are marginally larger with a slightly steeper forehead, and reliable sexing is by venting rather than by eye.
Feeding
The gut is long and adapted to algal turf, and this species is the one where a protein-heavy diet most reliably produces the fatal intestinal disorder the hobby calls bloat. The dietary restriction is not a refinement; it is the main husbandry requirement.
- Diet type
- Herbivore
- Staples
- Spirulina flake, Vegetable cichlid pellets, Nori sheet, Blanched courgette
- Avoid
- Bloodworm, Brine shrimp, Beef heart, High-protein pellets
Breeding
- Strategy
- Maternal mouthbrooding of very few, very large eggs
- Difficulty
- straightforward
- Parental care
- mouthbrooding
Broods are small — often under a dozen — and the fry emerge large and immediately independent, which is the trade-off for the low number.
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 | high | 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 | consumes | Tough species such as Anubias and Java fern survive most grazers. |
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.
- Mixing localities produces hybrids that cannot be assigned to any wild population. Given how many of these populations are small and separately threatened, that matters beyond the tank.
- Bloat in this species is usually well advanced before it is visible. A fish that stops eating and hangs at the surface has been unwell for days, and the response has to be dietary and immediate.
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
- Lake Tanganyika — many separate rocky-shore populations, principally in the south
- Habitat
- The upper few metres of the rocky shore, in bright light and surge, grazing algal turf from wave-washed rock.
What the checklists say
3 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 |
|---|---|---|
| Introduced | 1 | 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 | 2 | The source records the species as present and does not say whether it is native or introduced. AquariumHQ does not fill that in. |
No checklist AquariumHQ holds positively calls this species native anywhere, so the native range above rests on AquariumHQ’s own reading of the literature rather than on a cited checklist.
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 | Tropheus moorii | Observed / measured | high confidence | Catalogue of Life; GBIF — Global Biodiversity Information Facility |
| native range | Lake Tanganyika — many separate rocky-shore populations, principally in the south | Observed / measured | moderate confidence | GBIF — Global Biodiversity Information Facility |
| adult size | 11–14 cm | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| lifespan | 8–12 years | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| temperature | 24–27 °C | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| ph | 8–9 pH | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| general hardness | 12–22 °dGH | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| minimum tank volume | ≥ 450 L | AquariumHQ editorial position | moderate confidence | AquariumHQ husbandry synthesis |
| minimum tank length | ≥ 150 cm | AquariumHQ editorial position | moderate confidence | AquariumHQ husbandry synthesis |
| carbonate hardness | 14–20 °dKH | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| minimum group size | ≥ 12 | 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 2026-08-29. 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. 3 distribution statements held from GBIF checklists — introduced in 1 country. 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.
temperatureAquariumHQ'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.
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 volumeAquariumHQ'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 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.
carbonate 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 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.
Guides relevant to this species
Chosen from this record's own traits rather than listed on every page.
- Schooling and shoalingThis species is recorded as colony, and the number it is kept in decides how it behaves.
- Predator and prey sizeIt takes adult dwarf shrimp, which decides what can share the tank.
- Territorial behaviourIt defends ground, and the shape of what it defends decides the tank more than the volume does.
- Scientific and trade namesThe trade name for this animal covers more than one species.
- Wild conditions and aquarium recommendationsThe water band on this page is an AquariumHQ position with a stated reason, not a measurement of a river.
- How to read a compatibility verdictThis animal is recorded as nipping fins, which is one of the few compatibility factors with real reports behind it.
Group size and social behaviour
Kept in fewer than about a dozen, aggression concentrates on whichever fish is lowest in the order and it dies, then on the next. The large group is not a preference; it is the mechanism that spreads aggression thinly enough for the colony to survive.