A small, feisty brackish-water crab with bright red claws and a dark carapace, native to mangrove estuaries. It is semi-terrestrial and a notorious escape artist, requiring a tightly covered brackish paludarium with both water and accessible land.
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Small; carapace about 1.5-2 in (4-5 cm) wide, legs spanning up to ~4 in (10 cm).
Lifespan
2–4 years
Social needs
solo
Native region
Indo-Pacific mangrove estuaries (Southeast Asia)
Origin
Old World
Climate
🌴 Tropical
Water type
🌫️ Brackish
Family
Sesarmidae
Genus
Perisesarma
Part of the Freshwater crabs
Small crabs kept in aquariums and paludariums. Some, like the Thai micro crab, are fully aquatic, while many others (such as the red claw crab) are brackish and semi-terrestrial, needing both water and a dry land area to climb out and breathe air.
From the minimum an animal needs to be kept humanely, up to the ideal setup. Bigger is almost always better — minimums are floors, not targets.
Photo coming soon
Minimum
Brackish paludarium
10 gal (≈ 38 L), 50% land / 50% water
Perisesarma bidens is BRACKISH (SG 1.005), not freshwater — it dies slowly in pure FW. 50/50 land/water with deep sand land, hides, and easy water access. Tight-fitting lid — escape artists.
Photo coming soon
Recommended
Larger brackish paludarium
20 gal paludarium, land + brackish pool
A 20 gal paludarium with secure lid, deep sand land, mangrove roots, brackish pool with filtration, and gentle warmth (24–28 °C). Solitary in small tanks; pairs/groups need extra space.
Photo coming soon
Ideal
Mangrove biotope paludarium
30+ gal mangrove paludarium
A mangrove biotope paludarium with live mangroves, deep land, brackish pool, and varied structure. Generous footprint reduces aggression.
Life & growth stages
How this animal changes through its life — each stage often has its own care, diet and space needs.
Photo coming soon
Larva
Most marine invertebrates hatch into microscopic planktonic larvae (such as the zoea of crustaceans or the bipinnaria/veliger of echinoderms and mollusks) that drift and feed in the water column. The larva looks nothing like the adult and undergoes major reorganization.
Photo coming soon
Juvenile
After settling out of the plankton, the juvenile takes on a recognizable miniature of the adult body plan — a tiny shell, a small star, or a translucent shrimp. Crustaceans grow by molting, shedding the exoskeleton to enlarge.
Adult
Adults reach full size and reproductive maturity with the species' mature shell, shape, or coloration. Many continue to molt or grow throughout life, and some show sex differences in size or claw/appendage shape.
Habitat & enclosure
Set up a brackish paludarium of at least 10 gallons (40 L) per crab with both shallow water and easy-to-reach dry land; they breathe air and will drown if they cannot climb out. Crucially, the water must be BRACKISH, not pure fresh: aim for a specific gravity around 1.005 (about 1.2 tablespoons of marine salt per gallon), pH 7.5-8.5, temperature 75-82F (24-28C). Provide ramps, rocks, driftwood, and a haul-out area. A secure, tight-fitting lid is mandatory because they are determined escapers. Long-term keeping in pure freshwater shortens their lives.
Substrate
Use sand or fine gravel in the water zone and a land area of sand, coco fiber, or smooth stones they can climb onto. Avoid sharp substrate that could injure them. Aragonite/coral sand helps buffer pH and adds calcium for the brackish environment.
Equipment & setup
Essential gear: a tight-fitting, gap-free lid (escape-proofing), a heater for tropical temperatures, marine/brackish salt mix and a hydrometer or refractometer to set and check salinity, and gentle filtration. Include haul-out ramps and a cuttlebone or calcium source. Avoid copper-containing equipment or medications.
Diet
An opportunistic omnivore and scavenger. Offer a varied diet: sinking pellets, algae/spirulina wafers, blanched vegetables (peas, spinach, zucchini), bloodworms, brine shrimp, bits of fish or shrimp, and dried leaf litter. They forage on both land and in water. A source of calcium (cuttlebone, calcium-rich foods) supports molting. Feed every day or two and remove uneaten food. They will also graze algae and scavenge detritus.
Behavior & temperament
Bold, active, and territorial, especially males, which may fight or pinch tankmates. They are not social and are best kept singly or with ample space and hides to reduce aggression; crowding causes fighting. Their claws can pinch, so handling is discouraged and should be minimized. They will catch and eat slow or small fish and may uproot plants. They are primarily a display animal best observed rather than handled, and they are skilled escape artists, so security comes first.
Health
Generally hardy in correct brackish conditions but decline in pure freshwater over time. Common problems include drowning (no land access), escape and desiccation, failed molts from low calcium/iodine or poor water, and shell injuries from fighting. Provide a haul-out, brackish water, and calcium for molting. After molting they are soft and vulnerable, so give hides and avoid disturbing them. Never use copper-based medications. Acclimate gradually and quarantine new crabs.
Tips, DIY & hacks
Get the salinity right; this is the single biggest care mistake, as they are sold as 'freshwater' but truly need brackish water to thrive. Lid everything down tightly, as they climb cords and silicone seams to escape. House males singly or with lots of space to prevent fights. Provide a dry basking/haul-out area so they can leave the water at will.
