By Sophie Harding
Why nearly everyone buys vampire crabs wrong
You have seen a photo - a crab the colour of an amethyst with glowing yellow eyes - and you want one for your aquarium. Here is the problem almost every UK guide skips: a vampire crab is not an aquarium animal. Drop one into a normal flooded fish tank and it drowns. That single misunderstanding is the most common way these crabs die in their first week, and it is entirely avoidable.
I'm Sophie Harding, the invertebrate specialist here at Tropical Fish Co - shrimp, snails and crabs are my lane, and vampire crabs are the animal I get the most "why did it die?" emails about. Almost every one traces back to the same cause: the crab was kept like a fish. Vampire crabs are Geosesarma, a genus of small semi-terrestrial crabs from the forest streams of Indonesia. In the wild they climb roots and rocks at the water's edge and only soak in the shallows. They breathe air. They need land.
This page is the answer I'd give a customer standing at our tanks asking "can I just put it in my shrimp tank?" The short answer is no - you need a paludarium (part land, part shallow water). The longer answer, below, covers the colour forms we stock, how to build the enclosure, group size, what they really eat, how they moult and breed, and the honest truth about tank mates. Get the setup right and a vampire crab is one of the most characterful little animals in the hobby - they're alert, they recognise feeding time, and watching a group go about its evening on a mossy bank is a different kind of fishkeeping entirely.
I'll also be straight about where they don't fit. If you want a colourful animal to drop into an existing community aquarium, a vampire crab is the wrong choice and I'd point you at shrimp instead. If you're up for a small land-and-water build, though, you're in exactly the right place. Let's get it right from the start.
A vampire crab (Geosesarma) showing the trademark jewel colouring and raised eyes. Photo: Tropical Fish Co.
Fun facts - the stuff most UK guides never mention
The vampire crab is a young animal in science as well as the hobby, and it has a few genuinely surprising traits.
- The name has nothing to do with blood. The "vampire" tag comes from the glowing yellow eyes and the deep violet shell, not from feeding habits. The most-traded purple form was only formally described and named Geosesarma dennerle in 2015 [4] - the species name honours the German aquatics company that funded the field study in Java [2].
- They breed in fresh water with no larval sea stage. This is the headline. Almost every crab on Earth needs salt water for its drifting larvae. Geosesarma don't: females carry roughly 20-80 eggs under the tail and release fully formed miniature crabs straight into fresh water - "direct development" [2]. It is why a home paludarium colony can actually self-sustain.
- They are air-breathing climbers, not swimmers. A vampire crab spends most of its life out of the water, using modified gill chambers to breathe air, and will climb glass, silicone seams and plant stems with ease [1]. That is exactly why an open-topped flooded tank is a death sentence and a tight lid is non-negotiable.
- They hunt at dawn and dusk. Vampire crabs are crepuscular and nocturnal opportunists - they'll graze algae and moss, then seize a slow insect or sleeping shrimp when the lights dim [3]. Charming to watch, but it's also why they are not a safe community animal.
- There are dozens of colour forms and the genus is still being described. Many crabs sold as "vampire crab" are Geosesarma forms that science hasn't fully catalogued yet - new species from Java and Sulawesi are still being named [2]. The purple, orange, red, yellow and batik crabs we stock are part of that explosion of colour morphs reaching UK keepers.
Aquarium or paludarium? - the decision that comes before colour
Before you pick a colour, pick the right type of enclosure. This table sets the vampire crab against the two fully-aquatic inverts people most often confuse it with - because if you wanted "a colourful thing for my planted tank," one of the shrimp may actually be what you're after.
| What you're choosing | Vampire crab (Geosesarma) | Cherry shrimp (Neocaridina) | Amano shrimp (Caridina) |
|---|---|---|---|
| Lives underwater? | No - needs land | Yes - fully aquatic | Yes - fully aquatic |
| Enclosure | Paludarium (land + shallow water) | Standard planted tank | Standard planted tank |
| Needs a sealed lid? | Yes - escape artist | No | Helpful (jumpers) |
| Adult size | ~2.5 cm body, 4-5 cm legspan | 2-3 cm | 4-5 cm |
| Safe with small shrimp/fry? | No - opportunistic | Yes (adults) | Yes |
| Breeds at home in fresh water? | Yes (direct development) | Yes, easily | No (needs brackish larval stage) |
| Best kept as | Crab-only jungle display | Community-safe colony | Algae crew |
If the words "build a paludarium" already feel like too much, the right column is your animal - start with our cherry shrimp guide instead. If a land-and-water jungle excites you, read on.
Setting up a vampire-crab paludarium
A paludarium is simply a tank that is mostly land with a section of shallow water. It is the only correct home for a vampire crab. Here is the build I set up for our display crabs.
- Tank: 40 L minimum for a small group; wider beats taller (they roam horizontally). A standard 60 cm tank is ideal.
- The land/water split: aim for roughly two-thirds land, one-third shallow water. Build the land up with aquasoil, cork bark, slate or a false bottom; slope it down into a shallow pool only a few centimetres deep [3].
- A TIGHT lid - non-negotiable. Vampire crabs climb glass and silicone and will escape through any gap around a filter or cable [1]. Seal every opening. An escaped crab dries out within hours.
- Cover and climb-space: dense moss, cork tubes, leaf litter, driftwood and hardy plants (java fern, pothos rooted into the water, mosses). Plenty of hides stops territorial squabbles and gives newly-moulted crabs somewhere safe.
- Heat & filter: hold 22-28 °C with a small heater in the water section or a warm room; a gentle sponge or trickle filter keeps the shallow water clean without a strong current.
- Group & ratio: 3-5 crabs of a single colour form, one male to two or more females. Lone crabs hide forever; mixed colours muddy any offspring [6].
Every vampire crab loss I'm asked about is one of two mistakes. Drowning - the crab was kept in a flooded tank with no land to climb out onto. Drying out - the crab escaped through an unsealed lid. Get the land area and the lid right and you've eliminated the two biggest risks before you even choose a colour.
Moulting and breeding - what to expect
Two biological events define life with vampire crabs, and knowing them turns "is my crab dying?" panic into calm observation.
Moulting. Like all crustaceans, vampire crabs grow by shedding their shell. A crab about to moult goes quiet and hides; afterwards you'll often find what looks like a dead crab lying still - it's almost always the empty shed shell, and the real crab is tucked away while its new soft shell hardens over a day or two [3]. Never disturb a freshly-moulted crab, and leave the old shell in the tank - the crab eats it back to recover calcium. Persistent soft or deformed shells point to a calcium shortfall, so a cuttlebone or calcium-rich food in the enclosure is cheap insurance.
Breeding. This is the genuinely special part. Most crabs can't reproduce in fresh water because their larvae need the sea - but Geosesarma have direct development: a mated female carries roughly 20-80 eggs folded under her tail (her "apron") for about a month, then releases fully formed miniature crabs - no free-swimming larval stage at all [2]. In a settled, well-fed, single-colour paludarium with good cover, this can happen at home with no special intervention. The tiny crabs are vulnerable to being eaten, so dense moss and leaf litter give them the hiding space they need to survive.
Because vampire crabs breed true to type, a single-colour group (say, all purple) produces purple babies. Mix several colour forms in one tank and the offspring blur into muddy, indistinct crabs over a generation or two. If you ever want to raise young - or simply keep a clean-looking colony - keep one colour form per enclosure.
Which colour form should I pick?
All the crabs below are Geosesarma forms with the same core care - the same paludarium, the same diet, the same lid. The differences are colour and how widely available each form is. Care needs are effectively identical across the trade colour morphs [3], so choose on looks and on keeping one form per tank.
| Colour form | What you see | Notes |
|---|---|---|
| Purple (G. dennerle) | Violet shell, cream carapace patch, yellow eyes | The classic, best-documented form - described in 2015 |
| Vampire Orange / Banana | Warm orange to yellow body | High-contrast against green moss; very showy |
| Red Tomato / Red Carnaval | Deep red shell and legs | Bold colour; striking under dim evening light |
| Vampire Yellow / Golden Eye | Pale-yellow body, gold eyes | Lighter palette; reads well on dark hardscape |
| Batik / White-leg / Violet | Patterned or pale-limbed forms | Collector forms - rarer, prices a little higher |
There's no "hardier colour" - they're all the same care. Pick the colour you'll enjoy watching, then keep that one form alone so any babies come out the same colour.
What a vampire-crab setup actually costs
People budget for the crabs and forget the enclosure. Here's the honest shopping list for a small starter paludarium, so there are no surprises.
| Item | Rough UK cost | Why it matters |
|---|---|---|
| 3-5 crabs (one colour form) | £35-£80 | The animals themselves - our forms run roughly £11-£17 each |
| 40-60 L tank with a tight lid | £40-£70 | The lid is the part that keeps them alive - don't skip it |
| Substrate, cork bark, slate (land build) | £20-£35 | Builds the two-thirds land area they need |
| Moss, leaf litter, hardy plants | £15-£30 | Cover, grazing and humidity |
| Small heater + sponge/trickle filter | £20-£40 | Holds 22-28 °C and keeps the shallow water clean |
| Calcium source + crab/shrimp food | £10-£15 | Successful moulting and a balanced omnivore diet |
A realistic first paludarium lands around £140-£270 all-in. It's a one-off build - after that you're only topping up food and the occasional plant.
"Tank mates" - the honest version
Here's where I'll be blunt, because the welfare matters: vampire crabs are not a community animal. They're semi-aggressive toward other crabs and opportunistic toward anything slow or sleeping [3]. There is no list of "guaranteed-safe vampire crab tank mates" - any small fish, shrimp or shrimplet sharing the water risks being eaten at dusk.
So I don't frame the animals below as tank mates. I frame them as other inverts that suit a similar land-and-water build - usually in their own enclosures, occasionally cohabiting only if you've got the space, the cover and an acceptance of risk. The one genuinely peaceful, fully-aquatic exception is the Thai micro crab, which is too tiny and gentle to threaten anything (but is itself at risk from a vampire crab, so keep it separately).
- Shrimp keeping care guide - the foundations of invert husbandry (cycling, moulting, calcium) apply directly to crabs too.
- Nerite snail care guide - a tough algae-grazing snail that copes in the shallow water section better than soft-bodied shrimp; still no guarantee against a hungry crab.
- Shrimps & crustaceans hub - our full live invert range, including fully-aquatic options if a paludarium isn't for you.
Watch: a planted shallow-water invert tank
The clip below is a settled planted invert tank from our warehouse. It shows the kind of dense moss, leaf litter and gentle water a paludarium's water section should imitate - the difference for crabs is that you raise two-thirds of it into dry land they can climb out onto.
A red colour-form Geosesarma. Single-colour groups breed true; mixed colours produce muddy offspring over generations. Photo: Tropical Fish Co.
When your vampire crabs arrive - our welfare protocol
Vampire crabs ship via a licensed live-animal courier in damp, ventilated packaging - never standing water, because a sealed crab in deep water can drown in transit. Like all live crustaceans reaching the UK, Geosesarma are imported under the Fish Health Inspectorate's framework rather than bred here at scale [5], so the animal you receive has already had a long journey - gentle acclimation matters. It's a little different from fish or shrimp, because you're settling a semi-terrestrial animal, not a swimmer [6].
- Open in a dim, quiet room. Check the crabs are damp and active; they should be cool-to-warm, never hot or chilled.
- Keep them damp, never submerged. Mist them with dechlorinated water if the packing feels dry. Do not tip them into deep water.
- Float the transport tub on the water section for 20-30 minutes to equalise temperature.
- Add a little tank water to the tub in stages over 30-45 minutes so they adjust to your parameters gradually.
- Lift them gently onto the LAND area - never pour them into the water. Let them choose to enter the shallows themselves.
- Lid on, lights low for a few hours, no feeding for 24 hours. Expect them to hide for the first day or two while they explore - that's normal, not a problem.
Crabs moult to grow, and a freshly-moulted crab is soft, pale and defenceless for a day or two. If you see a "second crab" lying still it's almost always a shed shell, not a death - leave it, the crab will eat it back for calcium. Never handle or move a soft, newly-moulted crab.
What can go wrong - a diagnostic table
Most vampire-crab problems are environmental, not disease, and they show up as behaviour changes. Work down this table before you reach for any treatment - nine times out of ten the fix is the enclosure, not the crab.
| What you see | Most likely cause | What to do |
|---|---|---|
| Crab lethargic in deep water, won't climb out | No dry land / water too deep | Rebuild for two-thirds land; let it reach air immediately |
| Crab missing from the tank entirely | Escaped through a lid gap | Seal every opening around filters/cables; search warm dark corners fast |
| A pale, still "dead" crab on its back | Recent moult (shed shell) | Leave it - the crab will eat the shell back for calcium [3] |
| Soft, deformed new shell after moulting | Calcium deficiency | Add cuttlebone / calcium-rich food; check hardness sits 4-16 dGH |
| One crab constantly chasing/cornering others | Overcrowding or wrong sex ratio | More hides and cover; aim for 1 male : 2+ females |
| Crab hides for weeks, never seen | Kept singly, or too little cover | Add a small same-colour group; pile on moss, bark and leaf litter |
| Sudden deaths after a water change | Chlorine / parameter swing | Always dechlorinate; change the shallow water in small amounts |
| Tank mate (shrimp/fish) disappearing | Predation at dusk | Expected - vampire crabs aren't community-safe; separate them |
Your first 90 days with vampire crabs
A realistic timeline so you know what's normal and what isn't. Most new keepers worry in week one when the crabs vanish - that's expected, not a problem.
| When | What's happening | What to do |
|---|---|---|
| Before they arrive | Paludarium built and stable | Run the tank for 1-2 weeks first; confirm temperature 22-28 °C and a sealed lid |
| Days 1-3 | Crabs hide and explore at night | Lights low, no feeding day one, then feed lightly; don't go hunting for them |
| Week 1 | They start claiming hides and territories | Watch at dusk; check the lid seal again; offer varied food, remove leftovers |
| Weeks 2-4 | Confident roaming and surface climbing | Establish a light feeding rhythm; spot-clean uneaten food and old leaf litter |
| Weeks 4-8 | First moults likely | Leave shed shells in place; never disturb a soft crab; keep calcium available |
| Months 2-3 | Settled colony behaviour; possible berried female | If a female is carrying eggs, leave the tank undisturbed and keep cover dense for any young |
If a crab is still hiding permanently past week two and you're keeping it singly, that's the cause - add a small same-colour group and behaviour normalises.
Community, clubs and where to learn more
Vampire crabs sit in the wider UK invertebrate-keeping scene, which is small but genuinely helpful - and far better for honest husbandry advice than a quick web search. None of these are shops; they're hobbyist communities and references worth bookmarking.
- UK Aquatic Plant Society (UKAPS) - the main UK forum for planted tanks and paludariums; the place to ask about land/water builds and hardy emersed plants for a crab enclosure.
- Federation of British Aquatic Societies (FBAS) - the umbrella body for local UK aquarist clubs; a route to find a society near you that covers inverts.
- Practical Fishkeeping - the UK hobby magazine; their Geosesarma feature is a solid second opinion on the amphibious setup [3].
- Facebook "UK Crab & Paludarium Keepers" groups + Reddit r/crabs - active communities for build photos, moult questions and colour-form ID.
- Species references - for taxonomy and the genuinely surprising freshwater life cycle, the genus overview and the 2015 description paper are the primary sources behind this page [2].
For a video walkthrough of a full paludarium build and feeding routine, the care guide below is a good watch before you start [6].
Ready for more?
Vampire crabs sit at the crossover of the shrimp and snail world, so the husbandry foundations carry straight over from our invert guides.
- Learn: the shrimp keeping care guide covers cycling, moulting and calcium - all of which apply to crabs - and the nerite snail care guide is the best companion algae-grazer for the water section.
- Shop: the full live invert range is at the shrimps & crustaceans hub, and tough algae-grazing snails are at the snails hub.
- Compare: if a paludarium isn't for you, the fully-aquatic alternatives are our cherry shrimp guide and amano shrimp guide - colourful inverts that live happily in a standard planted tank.
