In short: Vampire crabs (genus Geosesarma) are small, semi-terrestrial freshwater crabs from Southeast Asia that need a land-focused paludarium: roughly 70–80 % land and 20–30 % shallow water, 22–26 °C, 70–90 % humidity, many hides and a lid that is truly escape-proof. A trio of one male and two females lives well in a tank of about 40 × 40 × 40 cm; a group of four to six crabs, ideally one male to two or three females, needs about 60 × 30 × 45 cm. Good vampire crab care is mostly about three things: stable humidity, enough cover for safe moulting and climbing structure from the water line to the top.
What are vampire crabs?
Vampire crabs are several species of the genus Geosesarma, found on islands and in rainforests of Southeast Asia. They live along small streams and in damp forest floor, often far from open water. Their common name has nothing to do with their diet: it comes from their glowing yellow or orange eyes, which contrast with dark purple, black or reddish bodies.
They are small. The carapace usually measures between one and two and a half centimetres, and with legs a large crab reaches a span of about five centimetres. Expect a lifespan of around two years, sometimes a little longer with good care. That short life is one reason why breeding in the tank is part of the fun for many keepers.
The biggest biological surprise is their development. Unlike most crabs, vampire crabs do not release larvae into the sea. The female carries her eggs under her abdominal flap, and fully formed miniature crabs hatch from them. That means they reproduce entirely in fresh water, and a well-kept group can breed in a home paludarium.
Vampire crab care: the key values
| Parameter | Recommended value | Note |
|---|---|---|
| Air temperature | 22–26 °C | Avoid more than 28 °C, especially in summer |
| Humidity | 70–90 % | Persistently dry air dries out the gills |
| Water : land | 20 : 80 to 30 : 70 | The crabs spend most of their time on land |
| Water depth | 2–8 cm, shallow edges | Dechlorinated fresh water, no salt |
| Group | 4–6 crabs, 1 male : 2–3 females | Several males fight over territory |
| Lighting | LED plant light, 10–12 hours | No UVB required |
| Activity | Dusk and night, shy at first | Become bolder in a well-structured tank |
How big should a vampire crab paludarium be?
For their size, vampire crabs use a surprising amount of space, because they climb and claim small territories. Height matters as much as floor area: a tall back wall effectively doubles the usable surface. A cube or a slightly tall tank works best. If this is your first tank with both water and land, our paludarium setup guide explains build order, drainage and filtration in detail.
| Group | Tank (W × D × H) | Background (W × H) |
|---|---|---|
| 1 male + 2 females | 40 × 40 × 40 cm | Custom size, approx. 37.5 × 37.5 cm |
| 4–6 crabs | 60 × 30 × 45 cm | 57.5 × 42.5 cm |
| Breeding colony | 90 × 45 × 45 cm | 87.5 × 42.5 cm |
Measure the inner dimensions of your tank before ordering; our background size guide shows exactly how. Remember that the lower part of the background disappears behind substrate and water.
How do you set up a vampire crab paludarium?
- Escape-proof the tank first. Vampire crabs climb silicone seams, tubes and cables with ease. Use a tight lid with fine mesh, seal every cable opening and leave no gap wider than a few millimetres.
- Build the water section. A shallow pool along one side or in a front corner, with a gently sloping exit of stones or roots. A small sponge filter or a tiny internal filter with a sponge-covered intake is enough.
- Raise the land section. Drainage layer, fleece and 5–10 cm of a damp mix of coco fibre, humus and some sand. Crabs dig burrows, so make it deep enough in at least one area.
- Fit the background. Silicone it to the glass so the crabs can climb it safely, and let it cure for 48 hours with the lid open.
- Add structure. Roots and branches leaning from the water to the back wall, flat stones, and at least one hide per crab.
- Cover the floor. A thick layer of leaf litter gives cover, food and humidity.
- Run the tank for a few weeks before the crabs move in, so humidity and the water section stabilise.
Why are hides so important for vampire crabs?
Like all crabs, vampire crabs grow by moulting. For a day or two after shedding the old shell, the new one is soft and the crab is defenceless, even against its own tank mates. In a sparse tank, moulting crabs are often attacked. In a richly structured tank, they disappear into a gap behind a root or into a burrow and come out again when hardened.
- Offer at least one hide per crab, better more, spread across land and the water's edge.
- Use leaf litter generously; it hides crabs and juveniles at the same time.
- Leave the shed exoskeleton in the tank for a day or two. The crab often eats it to recycle calcium.
- Never pick up or disturb a crab that is hiding for days. It is very likely moulting.
What do vampire crabs eat?
Vampire crabs are omnivores and opportunists. A varied diet keeps them healthy and colourful:
- Animal protein: fruit flies, small crickets, bloodworms, fish or shrimp food.
- Plant food: small pieces of vegetables and fruit, blanched leafy greens, algae wafers.
- Leaf litter: dried leaves are grazed constantly and are part of the natural diet.
- Calcium: a piece of cuttlebone supports the shell, especially for breeding females.
Feed small portions every other day in the evening, when the crabs are active, and remove leftovers after a day so they do not mould in the humid air.
How do you tell males from females?
| Feature | Male | Female |
|---|---|---|
| Abdominal flap (underside) | Narrow, triangular | Broad, rounded, covers most of the underside |
| Claws | Larger and more colourful | Smaller |
| Behaviour | Territorial, displays with claws | Calmer, carries eggs under the flap |
A berried female carries her eggs for several weeks. Give her peace and plenty of cover. The tiny juveniles hide in leaf litter and moss and need a tank without shrimp-eating fish or other predators.
Can vampire crabs live with other animals?
In practice, a species-only tank works best. Vampire crabs catch and eat shrimp, can harm small frogs and may hunt small fish that rest near the surface. Snails and springtails as a clean-up crew are usually fine. If you dream of a mixed paludarium, plan a much larger tank and accept the risk.
How can you tell your vampire crabs are doing well?
Healthy crabs are active in the evening, eat quickly, groom themselves regularly and climb into the upper parts of the tank. Warning signs are crabs that sit motionless in the water during the day, constantly search the lid for a way out, or never reappear after a moult. The most common causes are dry air, excessive heat or poor water quality in the small pool. A digital thermo-hygrometer at substrate level and a weekly partial water change prevent most problems.
When you buy, ask whether the crabs are captive-bred. Many vampire crabs in the trade are still wild-caught; captive-bred animals are usually hardier and settle in faster. Introduce the whole group at once if you can, because crabs added later to an established territory are often chased.
From the workshop: a back wall that crabs actually use
Vampire crabs are the reason many people discover how much a background can do. In a tank with bare glass walls, they sit on the floor and hide. With a textured root-and-soil wall, they climb to the top, sit on ledges and become far more visible in the evening. That is why we recommend root and soil models such as the Thin Roots In Soil Layers or others from our roots and soil backgrounds collection for crab tanks.
Because the tank is permanently humid, we finish these backgrounds with a coating made for wet conditions; please tell us it is for a paludarium when you order. If you need to hide a filter hose or the cable of a small pump, ask for a service chamber behind the background. That also removes one of the favourite escape routes, because the crabs can no longer climb the tubing.
For decor, our artificial wood never rots or moulds in the damp air, needs no boiling and gives crabs grip. A Driftwood Branch leaning from the pool to the back wall becomes a crab highway, and real-looking Decaying Forest Leaves add cover on top of the natural leaf litter.
FAQ
Are vampire crabs good for beginners?
They are a good first crab if you can keep humidity stable and build an escape-proof tank. Their care is not complicated, but they do not forgive dry air or open gaps.
Do vampire crabs need salt water?
No. Vampire crabs live and breed entirely in fresh water. Use dechlorinated tap water or soft bottled water in the pool.
Why do I never see my vampire crabs?
They are shy and mostly active at dusk. New crabs often hide for weeks. More cover, a dim evening light and a climbing background usually make them bolder.
Can vampire crabs drown?
They can stay under water for a while, but they need to leave it. Steep-sided pools without exits are dangerous, especially for moulting crabs and juveniles.
Planning your crab tank? Start with a climbing wall from our roots and soil backgrounds, made by hand to your tank size and finished for permanent humidity.