Vampire crabs, from the genus Geosesarma, are semi-aquatic invertebrates that make a great and interesting to watch pet. This genus currently contains around 58 recognised species. They are native to Southeast Asia, where they live in freshwater riverbanks, and feed nocturnally, though you will be able to see them during the day, especially at dusk and dawn. They have an average lifespan of 2-3 years in captivity, when kept in optimal conditions.
Physical description
Vampire crabs are bright in colour, often displaying shades of red, purple or yellow. One of the most popular colour forms is the red devil crab, which is dark brown and bright orange. Another common colour form is the bicoloured cream and purple morph. These crabs can grow to around 2 inches including legspan, with their carapaces reaching a maximum of 2.5cm.
Sexing
Male vampire crabs are usually a little bigger than females, and have larger claws that are bright in colour. Female crabs will have claws about half the size of those of males. Also, the underside of the male's shell will appear pointed, while a female's will appear rounder and wider.
Enclosure
A ten gallon tank (45L) can easily house around five or six crabs. They are very sociable creatures that enjoy living in a community. Water teemperature should be between 24C and 28C (75F-85F), with an optimal ph of 7.5-8.0. All water must be dechlorinated using TapSafe or other aquarium water conditioners. This is important as if the crabs are exposed to chlorine, they will die. The water also needs a filter, to prevent the water from becoming too unclean and causing a buildup of ammonia. Because their natural habitat is a freshwater riverbank, the goal is to create a small ecosystem of dense vegitation, rocky areas and riverbed. This can be achieved using live plants, driftwood and rocks to ensure the crabs have an environment that matches their home in the wild. It is important that the enclosure is around 50% aquatic, as these crabs will spend only around half their time in the water. If the crabs do not have an area in which they can climb out of the water, they will drown. In the freshwater area, a substrate of sand is best to aid molting and reproduction. It is a good idea to provide soil substrate in the terrestrial area of the enclosure to encourage natural behaviours such as burrowing. There must be spaces for the crabs to hide, so rocky crevices and mossy areas (using mosses such as java moss and sphagnum moss) can also be added to provide adequate hiding spaces for the crabs while they are vulnerable during molting ot during the daytime.
Feeding
Vampire crabs are crepuscular feeders, meaning they hunt down their prey at mainly dusk and dawn. They are omnivorous. Their diet consists of mostlty small insects, such as crickets and locusts, both dead and alive. Our advice to petkeepers is to feed with small flightless fruit flies and woodlice, as they are easy for the crabs to catch. They can also be fed fruit and vegetables (both rotting and fresh), earthworm pieces and springtails. These crabs will eat any moss or algae that is growing in the tank. They can also be fed aquatic food sources such as brine shrimp, bloodworms, fish flakes, pellets or other small shrimps and fish food.
Molting
Vampire crabs molt their exoskeleton every so often to allow the crab to grow. This process happens once or twice a year for adult crabs, but will happen more often for juvenile crabs under 6 months of age. The crab will often dig under the substrate to molt, or hide in a shaded area of freshwater. If you see a crab lying on its back, it is probably molting! Crabs are very vulnerable after their molt, so be careful when feeding insects that may bite, scratch or sting.
Breeding
Your vampire crabs will breed if they are thriving in optimal conditions. It takes about one month from mating to hatching of eggs. The females can carry 20 to 80 eggs at once, depending on her size. The eggs hatch within the mother, and she gives live birth to fully formed crabs into the freshwater. A freshly hatched crab will be only 1-2mm including legspan. They will stay beneath the mother's abdomen for several weeks, and after this period is over, the mother should be separated from her babies if you wish to prevent cannibalism, as the mother and other crabs in the tank will likely eat most of the young if left in the enclosure together.
FAQ
Why are they called vampire crabs?
Vampire crabs get their name from their shocking appearance, with bright yellow eyes and large menacing claws. They also owe their name to their hunting behaviours, as they feed at dusk and dawn, and are mostly nocturnal.
Why are my crabs acting lethargic/lazy?
This is most likely due to inadequate heating in the enclosure. The optimal temperature for your crab tank is 24C-28C (75F-85F). If the water or the terrestrial area is too cold, the crabs will become lethargic and uninterested in eating. An optimal temperature can be achieved with a heat mat on the side of the tank, and a small water heater if needed. Be mindful of the fact that these crabs are naturally shy and reserved and hiding is one of their normal behaviours. This is also in addition to them being nocturnal. Observe your crabs over a longer period of time and identify any behaviours that are unnatural for them. It is completely normal for your crabs to not want to come out during the daytime
Why are my crabs dying?
Is your water dechlorinated? These crabs are extremely sensitive to water condition and will die if exposed to the chlorine found in regular tap water. Is the water filtered? A build up of natural ammonia that occurs in the crab's waste can lead to health conditions if not properly filtered and cleaned. Your filter sponge should be cleaned once a week to remove any debris and ammonia in the water. Another way to reduce ammonia is to give the tank a partial water change every week or so, and a full tank clean once a month. A partial water change involves taking out some of the water (around half) and replacing it with fresh, dechlorinated water. During a full tank clean, retain some of the water that was in there already and take everything out of the tank, replace it with the water you retained, and do a partial water change as normal. Changing all of the water in the tank at once could remove necessary bacteria and ammonia that keeps your crabs alive. If you have been doing full water changes, this could be another reason why your crabs have died, however it is the least likely scenario, as this shouldn't kill the crabs immediately. If you have ordered some or all of your crabs online or from an untrusted source, it is unfortunately possible that they were imports. This means they were taken from the wild. Crabs taken from the wild are much more susceptible to disease and may introduce pathogens into a once healthy vampire crab environment. It is also possible that your crabs sustained an illness due to overcrowding during breeding and shipment, you should only purchase crabs from trusted sources with positive reviews.
Websites we recommend
Set Yourself Apart With A Pet Vampire Crab – Big Al's Blog
Vampire Crab – Detailed Guide: Care, Diet, and Breeding