Tioman vampire crab
A small orange-and-brown land crab from Tioman Island that lives beside water rather than in it, needing a humid terrestrial area with a shallow pool. Housing it in an aquarium full of water drowns it, which is the most consequential mistake made with the genus.
Quick profile
- Scientific name
- Geosesarma tiomanicum
- Adult size
- 2–3 cm (0.8–1.2 in)
- Lifespan
- 2–4 years
- Temperature
- 22–28 °C (72–82 °F)
- pH
- 7–8
- Hardness
- 8–20 °dGH
- Minimum tank
- 20 L (5 US gal)
- Minimum length
- 45 cm
- Swimming zone
- Bottom
- Social
- Colony — at least 4
- Diet
- Omnivore
- Overall confidence
- moderate confidence
What keeping this species involves
Straightforward once the enclosure is right and reliably fatal when it is not. It is a terrestrial animal that needs water rather than an aquatic one that tolerates land.
Damp leaf litter and stream margins in humid island forest, with the crabs spending most of their time out of the water.
Identity and names
- Common name
- Tioman vampire crab
- Scientific name
- Geosesarma tiomanicum
- Family
- Sesarmidae
- Order
- Decapoda
- Class
- Malacostraca
- Also sold as
- Geosesarma tiomanicum, Tioman crab, orange vampire crab
Adult size and growth
2–3 cm (0.8–1.2 in) — Carapace width. Leg span is roughly two to three times that.
Typical lifespan in an aquarium: 2–4 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: depressed — flattened top to bottom with a small terminal mouth. Assigned from what is typical of Sesarmidae, not examined for this species.
Water and tank requirements
A paludarium rather than an aquarium: most of the floor is damp land with leaf litter and a shallow pool at one end. The litre figure describes the pool and the footprint describes the enclosure.
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: Tropical island stream water, generally hard from limestone. The hardness supports moulting, which is where most Geosesarma losses occur; the temperature is the ambient of humid lowland forest.
Where these figures come from
Habitat class
Semi-terrestrial margin
Damp forest floor, stream bank and leaf litter beside water, where the animal spends most of its life out of the water and enters it briefly.
The water band is a provision rather than a habitat requirement, because the animal is not living in the water. What it is actually asking for is land, humidity and somewhere to shed.
- Conductivity
- 100–600 µS/cm
- Flow
- still
- Dissolved oxygen
- not characteristic
- Seasonality
- moderate
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 | 22–28 °C (72–82 °F) | Stability matters more than hitting an exact figure. |
| pH | 7–8 | A stable pH outside the ideal band is usually better than an unstable one inside it. |
| General hardness | 8–20 °dGH | Check your supplier's published figure before choosing species. |
| Minimum volume | 20 L (5 US gal) | A floor, not a recommendation. |
| Minimum footprint | 45 cm long × 30 cm deep | A paludarium rather than an aquarium: most of the floor is damp land with leaf litter and a shallow pool at one end. The litre figure describes the pool and the footprint describes the enclosure. |
| Water flow | still | Match the outflow to this rather than to the filter's rating. |
| Lid required | Recommended | Reduces evaporation and prevents accidents. |
| Structure | A deep damp substrate with leaf litter, cork bark, moss and planting, plus a shallow pool the crab can enter and leave freely. High humidity and a secure lid. |
Behaviour
- Spends most of its time out of the water on damp litter and enters the pool briefly to wet the gills.
- Climbs constantly, including up glass and silicone, which is why the enclosure has to be closed rather than merely covered.
Telling males from females
Males have a narrow triangular abdominal flap and larger claws; females have a broad rounded flap. The difference is clear once the animal is turned over.
Feeding
Eats leaf litter, small invertebrates and fruit. Live insects are taken readily and are what brings the animal out into the open.
- Diet type
- Omnivore
- Staples
- Leaf litter, Live insects, Sinking pellets, Blanched vegetables, Fruit
Breeding
- Strategy
- Direct development — a small number of eggs hatch as fully formed crabs
- Difficulty
- straightforward
- Parental care
- carries eggs
No planktonic larval stage, which is why this genus breeds in captivity when almost no other crab does. Broods are very small.
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 | 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 | none | Applies to snails you wanted as well as snails you did not. |
| Long or trailing fins | none | Fin damage is an entry point for secondary infection. |
| Plants | nibbles | 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.
- Kept in a full aquarium it drowns. The genus is repeatedly sold as an aquatic crab and this is the most consequential misinformation attached to it.
- Tioman is a small island and its endemic invertebrates have correspondingly small ranges. Captive-bred stock is available and is the better source.
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
- Malaysia — Tioman Island, in forest streams and their damp margins
- Habitat
- Damp leaf litter and stream margins in humid island forest, with the crabs spending most of their time out of the water.
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 |
|---|---|---|
| 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 | 1 | 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 | Geosesarma tiomanicum | Observed / measured | high confidence | Catalogue of Life; GBIF — Global Biodiversity Information Facility |
| native range | Malaysia — Tioman Island, in forest streams and their damp margins | Observed / measured | moderate confidence | GBIF — Global Biodiversity Information Facility |
| adult size | 2–3 cm | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| lifespan | 2–4 years | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| temperature | 22–28 °C | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| ph | 7–8 pH | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| general hardness | 8–20 °dGH | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| minimum tank volume | ≥ 20 L | AquariumHQ editorial position | moderate confidence | AquariumHQ husbandry synthesis |
| minimum tank length | ≥ 45 cm | AquariumHQ editorial position | moderate confidence | AquariumHQ husbandry synthesis |
| minimum group size | ≥ 4 | 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. 2 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.
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.
- Wild conditions and aquarium recommendationsThe water band on this page is an AquariumHQ position with a stated reason, not a measurement of a river.
Group size and social behaviour
Social in a large enough enclosure with enough hiding places. Males dispute over shelter and the disputes are mostly display where there is cover.