Red claw crab, also known as perisesarma Biden, is a tropical brackish water crustacean species found in mangrove swamps of the Indo-Pacific area.

They are aggressive and territorial particularly towards other red claw crabs. However, it is crucial to know that they are semi-aquatic as they can drown in a fully aquatic environment.

You can read all about the red claw crab in this article to gain adequate knowledge on how to care for them outside their natural habitat.

Red Claw Crab Stats

Red Claw Crab Size Leg span up to 4″ (10 cm)
Tank 10 gallon (minimum)
Strata Benthic
PH 7.5 to 8.5
Hardness dKH 8+
Temperature 75°F to 80°F (24°-27° C)

– Classification stats

Order Decapoda
Suborder Labroidei
Family Sesarmidae
Genus Sesarma
Species Bidens
Quick stats:
Listed tank sizes are the minimum
Size: Leg span up to 4″ (10 cm)
Tank: 10 gal minimum
Strata: Benthic
PH: 7.5 to 8.5
Hardness: dKH 8+
Temperature: 75°F to 80°F (24°-27° C)

– Name

The red claw crab is also known as red crab, (pseudo)sesarma moeschi, the Thai crab, the mini crab, perisesarma bidens, sesarma Biden, Grapus Biden

– Distribution

The red claw crab is originally from Asia, where they live along the coastlines and shallow swamps. Aquarius has also found them in mud flats in parts of the South China Sea, and Hong Kong waters through Singapore.

– General Body Form

The red claw crabs have flat shells, bulging eyes, and two identical claws. The two blades are on either side of the carapace. They do not have lungs; instead, they have a gill chamber which is directly below their carapace.

The carapace is located at their first legs region. The red claw crabs are semi-aquatic animals that can stay on land occasionally as long as their gill chamber contains a bit of water! They have rigid plates that cover their moist gills keeping dry air from getting in.

– Coloration

The red claw crab ranges from different hues of red to a flattering bright orange. Their exoskeleton is covered in random, brown-colored dots. However, the male red claw crabs have brighter colored shells than the female red claw crab. Their claw tips are yellowish, which could be a faint yellow color or a more solid shade.

– Size

The red clawed crab has a carapace that would grow to about two inches (5 cm) and a leg span of four inches (10 cm). However, their dimensions are smaller than other crabs, so aquarists fondly call them mini crabs.

– Lifespan

A tank-bred red claw crab lives for about two years but may survive longer if their habitats are suitable. However, the wild red crab lives for a longer period.

– Behavior

The red claw crab is naturally timid but more active when they feel no one is watching, like in the night-time. They are loners and would instead scour the bottom of their tanks alone. While the red claw crab scavenges for food, they try to move along very fast like they are in a hurry. The red claw crabs are tactful yet magnificent climbers.

They would quickly scurry away from a suspicious predator or even their tank if it’s open. The red claw crab can move in water effortlessly. They are always on the offense when they sight another red claw crab and raise their blade-sharp claws, ready to defend themselves.

If a red claw crab feels threatened be sure it would attack to injure their offender, particularly a small-size tank mate. Nonetheless, they may be less aggressive if they have more space or more hiding spots in the aquarium. The male’s dominance and power tussle issues cause them to appear hostile, but the females are more relaxed. They are like to chase off other females if they sight them.

The red claw crabs are predominantly hunters.

They prefer to stay in between aquarium plants as shelters and would hide there when they are uncomfortable. They also remain in these shelters when it is time to molt, and molting can take a couple of days. The red claw crabs are not interested in aesthetically pleasing habitats; rather, they are destructive. They would cut down and rearrange their tanks as they deem fit.

– Molting

The red crab claw has an exoskeleton, which means they have to shed their shell as they grow. The process is referred to by biologists as “molting.” The red claw crab takes only a few minutes to pull off its exoskeleton but takes a longer time to harden the new shell. During the period, which can take weeks, they are susceptible to attacks from opportunist predators!

Before the red claw crab starts to molt, it takes one day off from feeding and immerses in water for a while. By doing this, their shell cracks around the sides, giving it room to slid out easily. Some aquarists call it the breaking point because the red claw crab breaks out from its old shell and goes off to make another one. One fun fact about the red claw crab is that they can regenerate limbs; if they lose a pincher or leg during a contentious dispute, it will grow back. But it may take about two to four molting processes for it to regrow.

After a molting session, the discarded shell would resemble a dead crab with all body parts intact. Do not be alarmed when you see it in your tank, and do not take them out from the aquarium. The exoskeleton is like a calcium-enriched mine, and the red claw crab would gradually consume it as time goes on.

In some cases, the molting process does not go as planned. The red claw crab may get stuck and unable to leave its shell; it is quite a sad sight because you cannot help them fix it. You would have to wait and watch them figure it out.

– Sexing

The female red claw crab carapace measures between 10mm to 19mm. The male is predominantly bigger than the females. The male red claw crab has bigger and more colorful claws, while its shell is long and pointy. The female red claw crab, in comparison, has minor-sized and dark claws, and its underside is oval-shaped.

Red Claw Crab Care Guide

The red claw crab care consists of significant features to keep your pet crab as comfortable as possible. Here are the essential needs to consider.

1. Aquarium Type

It is crucial to remember that the red claw crab is not fully aquatic; they need to come out of the water from time to time or drown. In the red claw crab natural habitat, they come out from the swamps and stay on the shores occasionally. The ideal tank type for the red claw crab is a paludarium; it has room and features that accommodate aquatic, semi-aquatic, and land animals and plants.

2. Water Requirements

The red claw crab mangrove swampy home is partly euryhaline because it is close to the sea. Both water bodies mix; the mangrove’s fresh water and the sea, causing a mildly salty environment.

However, most aquariums would say they are strictly freshwater crabs, but that is not entirely true. The red claw crabs are brackish water species but barely survive in fresh water and flourish in the latter.

  • Water Parameters: The red claw crab has specific water needs, and getting it right is crucial to the red claw crab’s life span. To imitate their brackish water environment, you must mix some marine salt into their aquarium to turn it slightly salty. The water needs to be a sixth of the salinity of natural seawater. It is important to note that you have to keep monitoring replacing the salinity levels as you perform water changes. It should have a specific gravity reading of 1.005.

They thrive in shallow, warm hard waters that are mildly alkaline. You need to maintain the water temperature between 75°F to 80°F (24°-27° C), the PH range between 7.5 to 8.5 and Hardness of about dKH 8+. Also, check other water conditions reading so they remain well within their range. Get an accurate testing kit that would provide you reliable readings.

  • Filter: You would need an effective filter like a marine filtration setup; they do not affect the salinity levels as much as a regular filter. Change about 10 percent of the entire volume of the aquarium water weekly.

3. Tank requirements

The red claw crabs are unique, and their needs are slightly different from fishes. The minimum tank size for the red claw crab is 10 gallons. They are territorial mini crabs that need all the space they can get to flourish. However, the aquarium size is adequate for one male and a few female red claw crabs.

  • Tank decoration: The red claw crabs are destructive crustaceans that would pay no mind to your uniquely decorated tank. They want space to come out of the water and rest on the land or a surface at intervals. A paluadarium makes it possible because you can assign portions for water and land.

The red claw crab habitat should be mostly water with some land; you can share it using a 3:1 ratio. Randomly placed driftwood and aquarium shelter are essential for the red crab as they scare easily. They also help during molting seasons.

  • Aquarium plants; are also excellent choices for the red claw crab aquarium; they love the brackish water java fern. It shields them, but they cut them up unremorsefully. To get rid of their destructive behavior, place artificial plants in the tank.

4. Aquarium Land Portion

The land portion of your aquarium would contain sand. Most paludariums comprise of ready-made floating shelves that help you build the ideal home for your crab pet. However, whether you decide to construct a floating shelf or perch, make it sturdy enough for the red claw crab to get on and off.

5. Substrate

The ideal substrate for the red claw crab is sandy. These benthic creatures like to scour and burrow through the bottom of the tank. It mimics the substrates of their natural habitat and moves quickly as they play around it.

6. Aquarium Cover

The red claw crabs are crafty escapees; if given the opportunity, they run out of their aquarium. Cover your tank at the top firmly to keep them in. Some aquarists have complained about their pet crabs crawling into the water inlet tubes.

The red claw crab would not survive without water for long; instead, they would get dehydrated and die.

7. Tank Mates

The ideal red claw crab tank mates must be brackish water, aquatic creatures. They have to be species that understand the rules involved with territorial animals or constantly have clashed with the red claw crab.

Some suitable red claw tank mates are;

  • Fishes: they must be a non-aggressive fish breed that can swim fast and are top strata dwellers. They would stay away from the benthic-natured red clawed crabs, and in case the crabs show interest in them, they can get away quickly.
  • You should consider fishes like guppies, mollies, flag fish, tetras, some goby fish( do not put a bumblebee goby with the red claw crab),
  • Co-specifics: the red claw crab may not tolerate each other, so put one male and some female and space out their territory points. More than one male red claw crab is less likely to survive in the same tank. They are ready to fight to their death as only one would survive. A few females have such temper, but it is rare.
  • If possible, get the largest tank you can afford to reduce conflicts. Every red claw crab should be able to stay in its own space comfortably.

Unsuitable tank mate matches are;

  • Slow swimming, bottom-strata fishes: the red claw crabs are likely to catch and eat them.
  • Large predator fishes like black Crocker, sculpins, kelp rockfish, cabezon, East Pacific Red octopus, black and yellow rockfish, lingcod, copper rockfish, and sea otter
  • Do not add the red claw crab into an aquarium with more than one of these fishes, particularly the sea otter.
  • Male crabs: it would be wise not to put two male crabs in one tank. Their aggression is even more intense during mating periods.

Some hobbyists say their red claw crabs get fond of them enough to come close to them but be sure your aquarium crab will try to pinch you if you pick them up. They may feel irritated or threatened by physical contact.

8. Breeding

Some aquarium enthusiasts have reported that a tank-bred red claw crab breeding is almost inconceivable. However, other aquarists claim the red claw crabs are oviparous. They further say they have seen their eggs in the aquarium that did not hatch even after a long while nor survive when they do.

However, the red claw crab has seasonal mating periods throughout the year. The female crab reproduces and rests in between the seasons. The male and female red claw crab do not develop any parental instinct to protect their young rather; they are likely to eat them.

The baby red claw crabs are vulnerable larvae that are susceptible to diseases and physical harm. The red claw crab aquarium is a closed setting, so the larvae’s survival probability is very low. The larvae clear to scavenge for food at a very young age and would mainly rely on algae and microorganisms present in their habitat.

9. Diet

The red claw crabs diet consists of omnivorous meals. They are born predators but would rat anything you feed them. They enjoy vegetables like blanched peas, spinach, and other green leaves. They also eat high proteinous meals like blood worms, raw fish, raw shrimps, brine shrimps, pellets, and flaked fish.

In their natural habitat, they cut up leaves from mangrove trees with their claws to eat. However, commercial crab feeds would serve your red claw crab. They can eat algae-based pellets and some kinds of fish food, particularly the type that can sink to the bottom.

Conclusion

  • The red claw crab is benthic semi-aquatic animals.
  • They need both land and water to survive.
  • They are territorial and aggressive, particular towards co-specifics.
  • They eat plants and fleshy food like spinach and shrimps.
  • They molt to get rid of their exoskeleton.
  • They get along with top to middle dwelling fishes.
  • They are shy but active scavengers.

The red claw crabs are interesting animals that are easy to care for, particularly when you can meet their needs, but they do not live very long. You should get a red claw crab because it is an excellent addition to a paludarium setup.

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