Marlier's julie
The largest of the julies, chequered black on cream, and the one that most clearly does not care which way up a surface is. Pairs are strongly bonded, hold a small vertical territory, and are notable for the female being the larger and more dominant fish.
Quick profile
- Scientific name
- Julidochromis marlieri
- Adult size
- 10–14 cm (3.9–5.5 in)
- Lifespan
- 7–10 years
- Temperature
- 23–26 °C (73–79 °F)
- pH
- 8–9
- Hardness
- 12–22 °dGH
- Minimum tank
- 150 L (40 US gal)
- Minimum length
- 100 cm
- Swimming zone
- Bottom
- Social
- Pair
- Diet
- Carnivore
- Overall confidence
- moderate confidence
What keeping this species involves
Hardy, long-lived and unfussy about food, with the standard Tanganyikan water requirement. The complication is the same as with any strongly pairing cichlid: the pair has to form before the tank can settle.
Rock faces and the undersides of overhangs, where the fish moves along vertical and inverted surfaces as readily as horizontal ones.
Identity and names
- Common name
- Marlier's julie
- Scientific name
- Julidochromis marlieri
- Family
- Cichlidae
- Order
- Cichliformes
- Class
- Actinopterygii
- Also sold as
- Julidochromis marlieri, marlieri, chequerboard julie
Adult size and growth
10–14 cm (3.9–5.5 in)
Typical lifespan in an aquarium: 7–10 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
The territory is a rock face rather than a floor, so the requirement is a tall structure the pair can defend and enough distance from the next one.
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: Tanganyikan rock zone, slightly deeper than the shallow-shore species. The lower temperature ceiling reflects the depth this fish is collected from rather than a general preference for cool water.
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 | 23–26 °C (73–79 °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 | 150 L (40 US gal) | A floor, not a recommendation. |
| Minimum footprint | 100 cm long × 40 cm deep | The territory is a rock face rather than a floor, so the requirement is a tall structure the pair can defend and enough distance from the next one. |
| Water flow | moderate | Match the outflow to this rather than to the filter's rating. |
| Lid required | Recommended | Reduces evaporation and prevents accidents. |
| Structure | Stacked rock built up rather than out, with overhangs and vertical faces. Caves with a roof are what pairs spawn under. |
Behaviour
- Moves along rock surfaces in short glides, frequently upside down beneath an overhang.
- Pairs stay within a body length or two of each other and of the cave for most of the day.
Telling males from females
Females are larger than males, which is unusual enough that keepers regularly assume the opposite and separate a working pair.
Feeding
Picks invertebrates from rock surfaces at close range. It feeds facing the rock rather than the open water, so food that drifts past is often missed.
- Diet type
- Carnivore
- Staples
- Frozen cyclops, Frozen mysis, Small sinking pellets, Frozen brine shrimp
Breeding
- Strategy
- Eggs attached to the roof of a cave and tended by both parents
- Difficulty
- straightforward
- Parental care
- guarding
Broods are small and produced repeatedly, and older young are tolerated alongside newer ones.
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 | low | Anything that fits in the mouth is at risk once this species reaches adult size. |
| Adult dwarf shrimp | moderate | Cover reduces losses but rarely prevents them where the risk is high. |
| Shrimplets | high | 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. |
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.
- Julidochromis species interbreed readily and several are hard to tell apart as juveniles. A mixed tank produces fry of no determinable identity.
- The bond is real and its failure is violent. A pair that stops sharing a cave has usually already begun a conflict that ends with one fish dead unless it is separated.
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 — the north-western rocky shore
- Habitat
- Rock faces and the undersides of overhangs, where the fish moves along vertical and inverted surfaces as readily as horizontal ones.
What the checklists say
2 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 |
|---|---|---|
| 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 | Julidochromis marlieri | Observed / measured | high confidence | Catalogue of Life; GBIF — Global Biodiversity Information Facility |
| native range | Lake Tanganyika — the north-western rocky shore | Observed / measured | moderate confidence | GBIF — Global Biodiversity Information Facility |
| adult size | 10–14 cm | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| lifespan | 7–10 years | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| temperature | 23–26 °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 | ≥ 150 L | AquariumHQ editorial position | moderate confidence | AquariumHQ husbandry synthesis |
| minimum tank length | ≥ 100 cm | AquariumHQ editorial position | moderate confidence | AquariumHQ husbandry synthesis |
| carbonate hardness | 14–20 °dKH | Aquarium-literature consensus | 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 checkableLimited evidence — treat with caution.
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. 2 distribution statements held, and not one of them states an establishment means. Presence without native-or-introduced is not a native-range claim, so this stays below requirement rather than being read as one.
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.
Guides relevant to this species
Chosen from this record's own traits rather than listed on every page.
- Territorial behaviourIt defends ground, and the shape of what it defends decides the tank more than the volume does.
- 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
A bonded pair defends its rock and tolerates its own offspring for surprisingly long, so an established pair often shares the territory with several generations of young.