Red Claw Crab Care Guide: Everything You Need To Know

A red crab on the aquarium substrate
Dr. Mollie Newton
Published by Dr. Mollie Newton PHD| Senior Editor
Last updated: February 28, 2024
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For those seeking a new member for their micro tank or avid invertebrates enthusiasts who can’t get enough, red claw crabs might be your next tank member. We’ve compiled a comprehensive guide that covers all aspects from the initial tank setup to maintaining your crab’s health, so you can provide optimal care for this exciting crustacean!

Article Summary

  • Red claw crabs are brackish water species originating from mangrove swamps in the Indo-Pacific region.
  • They are often mislabeled as semi-aggressive, but their temperament depends on factors like tank space and hiding spots.
  • Red claw crabs are known to be escape artists, so it’s crucial to keep a tightly closed lid on the aquarium.

Species Overview

Common namesRed mangrove crab, red claw crab, red claws
Scientific namePerisesarma bidens
SpeciesP. bidens
Size2 in
Lifespan2 yr
FamilySesarmidae
GenusPerisesarma
DistributionSouth China Sea, Indo-Pacific
ColorRed, Flaming orange, yellow
DietOmnivore
TemperamentSemi-aggressive
Minimum tank size5 gal
Place in the tankBottom
Care levelModerate
BreedingDifficult

History and Background

Although originally used as fishing bait, it wasn’t until the 90’s that this crab was commonly kept as a pet. Nowadays, red claw crabs are seen as a quirky and exotic colored invertebrate to add to your aquarium. Typically found in the Indo-Pacific region of the world, these crustaceans require a brackish- not freshwater- tank. Learn more about this fun species by reading below! 

What is a red claw crab?

Red claw crabs are a brackish water crab species that have vibrant coloring and a high activity level.

Where did the red claw crab come from?

These little crabs come from mangrove swamps mainly in the Indo-Pacific region. They are semi-aquatic and will drown in aquarium setups that are fully aquatic. Due to their brackish nature, red claws tend to stick to shallow rivers and mangrove swamps of their natural environment and can not survive in freshwater.

Appearance

A Red Claw Crab Climbing On The Aquarium Plant
(1) A Red Claw Crab Climbing On The Aquarium Plant

With their bright red body and yellowish claws it’s no wonder these crabs are a hit with aquarists looking to brighten up their tank.

What do red claw crabs look like? 

Like all crabs, this species has eight walking legs and two claws at the front of their body. Along each leg are fine hairs that help the crabs sense and interpret things in their environment such as food and predator pheromones. Red clawed crabs come in a variety of colors ranging from red to bright orange though males generally have more vibrant coloring than females. At the front of their body they have darker claws that have yellow tips.

How big does a red claw crab get?

This species is known as mini crabs as their carapace will grow to be roughly 2 inches and their leg span roughly 4 inches. Total size depends on the conditions that they were raised in.

How fast do red claw crabs grow?

Red claw crabs will generally reach their adult size at 6 months of age. This can vary slightly based on genetics and environmental conditions.

Male vs Female Red Claw Crab

The easiest way to differentiate between male red claw crabs and female red claw crabs is to flip them upside down and look at their apron. Male crabs will have a narrow and pointed apron whereas the female’s will be wide and round.

Temperament and Tankmates

Crab inside a home aquarium
(2) A Red Claw Crab In A Home Aquarium

These crabs generally get mislabeled as semi-aggressive, but we think they’re just a bit misunderstood. That’s why we’ve answered the most commonly asked questions about tankmates for this species as well as compiled a list of suitable (and not so suitable) companions. Read on to learn how to properly pick companions for this crab and keep a happy, healthy tank.

Are red claw crabs aggressive?

The red clawed crab is generally a timid and shy species, but when confronted it tends to attack first. Because of this these mini crabs often get a bad reputation as aggressive, but besides species-specific male dominance and power dynamics they tend to mostly keep to themselves.

Can you keep red claw crabs together?

Males tend to become extremely territorial in the aquarium so if you are planning on keeping multiple of this species be sure that you choose either one female and one male or multiple female crabs. Aggression will decrease with the amount of tank space and hiding spots as this will allow the adult crabs to escape to their individual areas.

What fish can live with red claw crab?

Tank mate requirements are very specific when it comes to red clawed crabs. Suitable tank mates have to tolerate brackish water, be non aggressive, dwell in the upper region of the tank, and not consider the red clawed crab as food.

Compatible tank mates

  1. Mollies-a small and popular aquarium species that will stay in the upper portion of the tank and is considered to be very peaceful.
  2. Tetras-smaller tetras such as neon tetras would make excellent tank mates for red clawed crabs as they wouldn’t be able to chase them (tetras are fast swimming fish), and the crab would avoid the large school of fish.
  3. Gobies-certain types of gobies will get along well with red claws, however, one of the most popular-the bumblebee goby- will not.
  4. Figure 8 puffer-more experienced aquarists can try keeping these species in the same tank. The puffer will only grow to be 3 inches large meaning they can’t swallow adult red claw crabs, but they are tagged as semi-aggressive.
  5. Endlers Live Bearers-similar to guppies but slightly smaller, this small fish won’t bother your crabs.

Other tank mates that could do well with your crab include guppies, and dwarf shrimp (if acclimated properly). Remember that most freshwater crustaceans will not be able to survive in the brackish water that red claw crabs need to survive. It is also worth noting that some aquarists use species specific tanks (mostly female crabs) for their crabs because of the difficulty involved in finding a compatible tank mate.

Tank Mates to Avoid

  1. Black and yellow rockfish-a large predator fish that will likely go after your crabs as a meal.
  2. Sculpins-despite their flattened head these spiky fish can open their mouth wide enough to fit a red claw inside.
  3. Kelp rockfish-this larger fish, though slow moving, will make short work of any of your crabs.
  4. Other Aquarium Crab Species – other crab species like the vampire crab or the fiddler crab will not get along well with the red crab as they are all territorial and will likely end up fighting each other.
  5. Cabezon-another spiky fish friend, it is unlikely that they will see your crabs as anything other than their next meal.

Tank Requirements

Fish Tank With Tropical Coral Reef Aquarium
A Saltwater Tank

The main requirement for tank upkeep when it comes to this species is ensuring that proper salinity requirements are maintained. For those who aren’t used to keeping a brackish tank, this may take some getting used to. Luckily, we have all the information you need to know listed below.

Water Parameters 

Tank Size>5 gal
Water TypeBrackish
Water Temperature75-80
Water pH7.5-8.5
Water hardness>8 dKH

Tank setup:

What kind of Substrate to use?

You should ideally have a sandy substrate along your tank floor. This tank setup will replicate their natural habitat and as red claw crabs prefer burrowing, will give them an opportunity to do so. Additionally, sand can be piled onto one side of the aquarium to create a shoreline and provide the red clawed crab the semi-aquatic that it needs. Just be sure to keep the water line a few inches below the top of the substrate.

How to choose a filter?

You should choose a strong filtration system similar to one that you would have in a marine tank. As brackish tanks still contain a considerable amount of salt, having a marine rated filter will prevent your filter from decaying due to the marine salt.

Do I need a pump?

A pump is not necessary for keeping red claw crabs as they are used to a slow moving environment.

Should I have a Water heater?

A water heater is absolutely needed for this mini crab as its natural habitat is considered a tropical area.

What kind of Lighting to use?

Red claw crabs don’t need specific lighting requirements and therefore you can cater to the needs of other fish or plants in your tank.

What size tank does a red claw crab need?

Due to their small size this mini crab can be housed in a 5 gallon tank. However, if you want to keep a male and female adult red claw crab together you need a minimum of 10 gallons. This larger tank setup will ensure that each crab has enough territory for itself.

Do red claw crabs need land?

Yes, red claw crabs are a semi-aquatic species and can not spend all of their time in the water. As such you should plan to have a portion of your aquarium be devoted to terrestrial habitat much like a paludarium with land and water elements, or make floating perches out of driftwood.

Do red claw crabs need saltwater?

No, red claw crabs require conditions that are ⅙ the salinity level of natural seawater (1.0278).

How to make brackish water for red claw crabs

Red claw crabs live in brackish conditions or a reading of 1.005 specific gravity. To create this add marine salt to a freshwater tank and mix.

How to set up a red claw crab tank

When beginning tank setup it is best to start by preparing the brackish water and cycling the tank. Once the tank is stable and well established you can add substrate and build out the terrestrial portion of the habitat. Be sure to be consistently testing the water parameters of the aquarium to ensure that they are cycled.

Water/Land Ratio

The optimum water to land ratio for red claw crabs is 3:1. In other words, for every 3 gallons of water you have in your tank you should account for 1 gallon of terrestrial space. 1 gallon of water is roughly equal to 231 cubic inches.

Do red claw crabs need plants?

Aquarium decorations such as plants and caves are required for this species as these crabs spend much of their time hiding and scuttling back and forth between hides.

Diet and Health

Bloodworms in White Background
Bloodworms in White Background

Planning a well balanced and nutritious diet catered directly to aquarium species is vital for their health, disease prevention, and promoting a long life.

What do red claw crabs eat?

In the wild red claw crabs are considered omnivores and opportunistic feeders. This means they will eat anything they can, anytime they can.

What to feed red claw crabs?

In a balanced diet red claw crabs need to have roughly 80% protein intake and 20% plant matter. For protein you can choose between sources such as bloodworms, brine shrimp, uncooked fish, daphnia, or insect larvae. Plant matter options include leafy greens that have been washed and blanched or algae pellets.

TIP

Shrimp pellets work surprisingly well as food for crabs as they are another crustacean and their pellets are specifically made to increase shell color vibrancy and strength.

How often do you feed red claw crabs?

As red claw crabs are mostly nocturnal it can be difficult to schedule feeding sessions for them. The best technique is to drop their food in the aquarium at night, allow them to hunt overnight, and clean up any remaining food in the morning.

TIP

Red claw crabs are escape artists, be sure to keep a lid on your aquarium and close it tightly after each feeding.

How often do you feed red claw crab?

You should plan to feed adult crabs once daily and juvenile crabs twice daily.

How much do you feed red claw crabs?

Feed your red claw crabs roughly 1 teaspoon of food per crab. This will give them enough nutrition without actively overfeeding them. However, if you notice more aggression than normal and suspect they are not getting enough food you can increase the amount they are being fed.

Common diseases of red claw crabs?

There are no species specific diseases for this craband it is fairly susceptible to them. However, like all crabs in poor water conditions it can contract shell infections. Symptoms include pockmarks along the length of the leg span as well as along the body. In severe cases the disease can eat its way through the shell and prove fatal for your crab. It is generally caused by bacteria so treatment with a broad-spectrum antibiotic can help. Be aware that crabs cannot have medicines that contain copper.

FUN FACT

Interestingly, crabs can carry it but aren’t affected by it. Remember to quarantine all tank members before adding them to avoid this!

How long do red claw crabs live?

In captivity red claw crabs tend to live for 2 years. In the wild their lifespan is increased to roughly 6 years but ultimately their life in the aquarium depends on the quality of red claw crab care.

How long do red claw crabs live?

Breeding

Breeding this species is unheard of and little information is known about how they reproduce. Read on to find out what we do know about these crabs’ reproduction methods.

Can you breed a red claw crab?

There is not much literature on breeding red claw crabs because it has never been recorded in captivity.

How to breed a red claw crab?

The things we do know about breeding red claw crabs is that they have seasonal mating periods throughout the year and have no parental instinct.

Baby red claw crab care is difficult because they are extremely susceptible to disease. Additionally, larvae can not be fed regular hatchling food such as brine shrimps because they are too small. Instead they will eat algae or other microorganisms.

Here’s a video on how red claw crabs breed.

Red Clawed Crab (Sesarma bidens) – Copulation & Care of eggs

Red claw crab FAQS

Are red claw crabs easy to take care of?

Red claw crab care is moderately difficult mainly because of their brackish requirements. Unlike the thai crab and other freshwater crabs this species cannot survive in freshwater so it is of the utmost importance that you monitor salinity levels closely.

Can you hold a Red Claw Crab?

Some aquarists report that their crabs like being held, while others say they are quite avoidant of human interaction. It depends on your crabs personality, but if they are scuttling away from your hand do not pursue picking them up unless absolutely necessary as you will likely be pinched.

How long can red claw crabs stay underwater

This species has gills, so they can actually spend as much time underwater as they want. If they go on land they will have to return to the water before their gills dry out.

Do Red crabs escape?

Yes, you could say this species enjoys the fresh air because they are constantly trying to find tank decor to climb on top of and escape their enclosure.

Why is my red claw crab upside down

The most likely reason is that your crab is molting or shedding its outer shell for a new one. This is a completely normal occurrence and some crabs will burrow into the sand to molt and lie upside down as it is an easily defensible position.

Is the red claw crab for you?

Whether you’re planning for a crab only micro tank, or want to make a community brackish tank the red claw crab will fit perfectly in your next aquarium.

Conclusion

In conclusion red claw crabs are an excellent addition for beginner to moderate leveled aquarists looking to break into the world of invertebrates. They are not susceptible to disease, easy to feed, and relatively easy to manage making them the perfect invertebrate.

Featured Image – JSutton93, CC BY-SA 4.0, via Wikimedia Commons
(1) Marrabbio2, CC BY-SA 3.0, via Wikimedia Commons
(2) RockStarRei at English Wikipedia, CC BY-SA 3.0, via Wikimedia Commons

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