How To Keep Your New Red Claw Crabs (Sesarma Bidens): Full Care Guide

March 26, 2024

Red claw crabs, otherwise known as Preisesemara Bidens, are a tropical brackish species that are wonderfully fascinating to own.

Originating in the swamps of the Indo-Pacific region, they boast vibrant, beautiful colors and, thanks to their active lifestyle, you will never be bored when owning one of these little crustaceans.

Although exciting and entertaining, red claw crabs can also be overly aggressive, especially compared to most other brackish crustaceans.

If you’re new to owning a red clawed crab, then these aggressive tendencies may take you by surprise. That is why you need to understand how to care for these creatures correctly and safely.

How To Keep Your New Red Claw Crabs (Sesarma Bidens): Full Care Guide

One critically important piece of knowledge about these crabs is that they are semiaquatic. Therefore, they should never be left unattended in a fully aquatic space. If so, they will probably drown. 

This is just one aspect to think about when owning a red claw crab.

Today, we are going to guide you through so much more so you can have the best understanding possible about how to look after these intriguing crabs.

We will study their diet, tank setup, average lifespan, and much, much more.

So, let’s get started with your journey of owning red claw crabs!

Red Claw Crab Information

Scientifically known as Perisesarma Bidens, red claw crabs are certainly a unique species. If you like to keep an array of different animals in aquariums, the red claw crab may be a whole new ball game in terms of entertainment and care.

Yes, they may seem pretty defensive and even shy, but there’s no doubt about it, red claw crabs are some of the most characterful crustaceans out there.  

Red claw crabs are originally from regions in Asia, while their habitats are mostly found in estuaries and shallow rivers. This is why they are regarded as brackish creatures, as their habitat tends to be slightly salty. 

One misconception about these crabs is that they are freshwater crustaceans, but this is not the case.

Yes, they can survive in a freshwater environment, but their life expectancy will not be as long as in their natural habitat.

That is why they must have some brackish water to live in.

Over the last few decades, red claw crabs have increased substantially in popularity. However, there remains an abundance of misconceptions about these vibrant creatures.

Like many invertebrates, red claw crabs are totally unique and require specific care and needs.

Before we look at the lifespan of red claw crabs, here are some quick and helpful stats to give you a better understanding of what tanks they require:

  • Minimum tank size – A leg span of up to 4 inches (10 cm)
  • Minimum gallons – 10 gallons
  • Strata – Benthic
  • PH value – 7.5 – 8.5
  • The hardness – dKH 8+
  • Tank’s temperature – 75 degrees Fahrenheit – 80 degrees Fahrenheit (24 degrees Celsius – 27 degrees Celsius)

Red Claw Crab – Lifespan 

The lifespan of a red claw crab in captivity is typically between two and two and a half years. However, some can live longer than this.

As with all aquatic creatures, these crabs are very sensitive to water, so in order to live for 2.5 years, they still require the best possible environment to live in. 

As we have mentioned, red claw crabs are unique and special invertebrates. That is why they need unique and special care.

Unfortunately, due to misconceptions and poor educational resources, red claw crabs are often advertised as freshwater aquatic creatures. But, they are not. Red claw crabs must have brackish water and fresh air to thrive healthily. 

If you keep red claw crabs in a freshwater environment or with little access to fresh air, they will live for a considerably shorter time. In fact, they may only live for a few months.

Although getting their environment right in the beginning, you still need to maintain the water’s condition regularly and keep on top of things.

If their brackish water is not looked after sufficiently, the crabs could become stressed, catch diseases, and, even, die.

Red Claw Crab – Size

Red Claw Crab - Size

The red claw crab is not a large species. In general, a typical red claw critter will measure around 4 inches. This measurement is taken in leg span.

Because of their small stature, many refer to these as ‘mini crabs.’ Also, their carapace is very small, with their main body only measuring approximately two to two and a half inches in width.

As we said – mini crabs! 

Red Claw Crab – Appearance

When you first lay your eyes upon red claw crabs, you will be bedazzled by their wonderful and unique features.

Compared to many other crustaceans, red claw crabs are exquisite and truly stand out from the crowd.

Nevertheless, as with most crustaceans, the red claw crab’s main body is generally a neutral brown color with a few spots to act as camouflage.

There may also be a few dark black patches that spread across the top of their heads, too. This is usually situated in the center of their carapace.

Looking at the two sides of their heads, you will see two, large, bulging eyes, almost like antennae. 

As for their most identifiable feature, it has to be their vibrant red claws, but their tips can sometimes be orange or yellow, as well.

Of course, the brightness and color can alter between one crab to the next, but every single red claw crab has red claws.

Overall, these critters sport ten legs, with the first eight being used for walking in sandy regions. These are not as colorful as their claws and are particularly pointed. 

As for the sexes, there are only small differences between male and females. The male red claw crabs tend to have thicker, meatier claws and typically have more vivid colors.

But, as with most crab species, turn the red claw crab upside down and you can distinguish males from females from their undersides.

Here, you will see a flat flap. In males, this is either pointy or triangular, whilst with females, it is broader and more rotund. 

Red Claw Crab – Behavior

Although naturally timid, red claw crabs are active little creatures when left alone, such as in the night. More often than not, red claw crabs prefer to be alone and will spend a lot of time at the bottom of their tanks.

Here, they will scavenge for food and move very quickly, as if they are in a rush to get somewhere.

Watch them do this and you will soon see how tactful their red claws are, allowing them to be excellent climbers.

When in water, these crabs move around with ease. They are always on the offensive if they see another red claw crab. When this happens, they will raise their claws and get ready to defend for their lives.

This can make for an entertaining few minutes! 

But, entertainment can quickly turn nasty as red claw crabs can attack and injure another if it feels threatened. However, the females are more relaxed than the aggressive, dominant males.

More often than not, males will chase other females off if they see them. Nonetheless, if your little red claw crabs have enough space and hiding spots, they will be less aggressive. 

It’s important to note that an aesthetically pleasing tank is not of top priority for these little guys and girls. They are natural hunters, so can be pretty destructive to everything around them.

They generally prefer to hide amongst plants, especially when they feel uncomfortable. Red claw crabs also molt, so they usually hide in plant shelters to molt for a few days.

After this, they start to rearrange their tank’s environment to suit them. 

Red Claw Crab Care Guide

Red Claw Crab Care Guide

Now, let’s find out how to care for red claw crabs safely and effectively. These critters require unique conditions to thrive.

Their habitats need to be crafted with precision and, once prepared, they must be monitored very closely. 

You’ll be pleased to know, though, that preparing the habitat is not too hard, once you know what you’re doing. First thing you need to know is the tank size, so let’s study this.

Tank Size

In general, the tank size for red claw crabs should be at least 10 gallons. Whilst it is possible to keep these crabs in 5 gallon tanks, there is no harm in having larger environments for them.

Yes, they may be small creatures but they need a lot of space to swim around, explore, and claim their territory. 

10 gallon tanks are generally large enough for a male and two females. But, the more space they have, the better. If needed, go for an even bigger tank.

Remember, red claw crabs are extremely territorial and can be aggressive so, having more space lowers the risk of altercations between them. 

Water Environment 

The parameters of the water in your red claw crab’s tank is one of the most important factors to get absolutely right.

For these crabs to stay healthy and happy, their tanks need to replicate their natural environment. 

Most red claw crabs are found in shallow Asian waters, mostly in mangrove swamps near coastlines.

Therefore, your tank’s water should be like these waters – brackish, hard, and somewhat alkaline. 

Out of these conditions, brackish, maybe the most important element.

To make the tank water brackish, add some marine salt to it for a little salinity. Compared to ocean water, this is around a sixth of its saltiness. 

To get the water precisely right for your red claw crabs, follow these guidelines:

  • Water temperature – 70 degrees Fahrenheit – 88 degrees Fahrenheit (ideally, aim for the middle of this)
  • Water hardness – 8 – 25 dGH
  • pH levels – 7.5 – 8.5
  • Gravity – Specifically, 1.005

Even when you have their water setup perfectly, the work doesn’t stop there. You must perform regular tests on the water to ensure it is meeting the right requirements.

Setting Up The Tank And Its Interior 

You can be forgiven for thinking setting up a tank for crustaceans can be an arduous process. But, it doesn’t have to be! Putting together a tank for red claw crabs can be pretty fun!

As we mentioned before, red claw crabs require both land and water to remain healthy and happy. In ideal circumstances, their tanks should have a water to land ratio of approximately 3 to 1.

So, their tanks should be filled primarily with water but with some land formations, so your little friend can have a place to relax.

To build the perfect tank environment for red claw crabs, start by adding some sand substrate. We recommend sand for red claw crabs as they love to scavenge, dig, and burrow.

And, because sand is so easy to maneuver, they won’t have to work too hard when doing so. 

If you’re using a traditional aquarium, you can set up a landmass using sand. You may find that some already have built-in shelves to make it easier to build landmasses.

If not, you can use floating perches. 

When it comes to the water, we suggest adding several decorations that are natural to a red claw crab’s environment. Examples include driftwood and rocks.

With these, the crabs can use them if they feel threatened or scared for any reason. Think of these decorations as safe havens for your little pets.

As well as this, these decorations will be very important for when the crabs begin to molt. 

You should also add plants. Just bear in mind that red claw crabs are renowned for uprooting and shredding plant leaves.

Their claws are very sharp and it will take them no time at all to completely decimate the plants in their tanks.

One plant that red claw crabs adore is Java Ferns so consider adding these.

But, if you try real plants and they are destroyed quickly by angry red claw crabs, try using silk plants instead. 

Hugely important is a strong filtration system. We recommend utilizing a marine filtration system for the best conditions.

These can cycle the water more efficiently without causing any change to the salinity levels. Nevertheless, we also recommend doing a 10 percent water change once a week to maintain good water levels. 

Finally, you need to find a strong, durable lid to place on top of the tank. Red claw crabs may be quite docile most of the time but they are also incredibly apt at escaping.

Some have been seen crawling up inlet tubes and escaping through the smallest of gaps. If this happens, the crab may not live for very long, as they will quickly dehydrate without access to water.

Therefore, ensure your tank’s lid is on firmly so they can never get out without your help. 

Food And Diet

Although red claw crabs are pretty predatory, they are omnivores. Therefore, they will eat almost anything you give them.

When they are predatory, however, it is usually more to do with their territories rather than food. 

A healthy red claw crab diet should be varied with proteins and vegetables.

In particular, bloodworms are a favorite snack for red claw crabs as well as uncooked pieces of fish, shrimp, and whole brine shrimp. 

When in the wild, these crabs tend to eat a lot of mangrove leaves every day. This is why you may see them chew on any plant leaves you put in their tanks.

As well as shrimps, fish, and mangrove leaves, regular commercial food can be fed to fed claw crabs, too.

Algae pellets and sinking fish food will be enjoyed by the crabs but, in general, they prefer other types of food. 

Tank Mates

You should not keep red claw crabs with another species. Because they are territorial, they are known to fight. Also, their brackish environment means other species may find it hard to live in such conditions. 

Although some aquarists have kept peaceful fish in the same tanks as red claw crabs, they have been fast-swimming species that stay mostly at the top of the water.

If you want to go down this route, ensure the other fish species meets these criteria. Examples of fish that could work well are Mollies, larger Gobies, and Flagfish. 

Overall, your best bet would be to keep just a small number of red claw crabs in the same tank, such as one male and two females.

You should not keep more than one male red claw crab with another, as they will become aggressive and fight. 

In Summary

Red claw crabs are one of the most fascinating and exciting species of crustaceans to own.

But, they come with particular requirements and conditions to live happily and healthily.

We hope this guide has given you a better idea of how to care for your new red claw crabs properly so they live happy, long lives.–2Q
Jose Viacrucis

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