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Red Clawed Crab Care: Diet, Size & Lifespan Explored

In this world, there are over 4,500 species of crab, but none are as breathtaking as Red Claw Crab. From their beautiful dark shells to their practically glowing red claws, the Red Claw crab has become something of a designer pet.

Due to the rise in the demand for this rather gorgeous crustacean. I have taken on the task of creating a beginner’s guide to everything one might need to know about the Red-Claw Crab. Call this the Red Claw Crab 101 Guide!

The Perisesarma Bidens (the scientific name for the Red Claw Crab species) are small crabs with dark, almost black, shell save for their claws which are bright red thus lending to their memorable name. They are located natively in the Indo-Pacific region from Japan and Fiji to Zanzibar.

They are particularly comfortable in shallow rivers and estuaries, specifically those that connect with the vast sea. Whilst they can survive in freshwater, it is not ideal for them too and instead require brackish water in order to live up to their full lifespan. According to many owners of the Red Claw Crab they say that the crabs are colorful in their character albeit defensive and timid.

Let us start with the first point of contention about this absolutely adorable fellow and that is their lifespan. In the wild it is currently believed that Red Claw Crabs live on average about two years, however, more studies need to be conducted in order to prove this. In captivity, however, they have been observed to live anywhere between two and five years if appropriate conditions are met.

This displays that, unlike many other pets, the red claw crab is a relatively short-lived species. Like with all species with short life spans, this tends to be tied with how they mate. Thus onto our next point.

Breeding Red Claw Crabs in captivity is challenging to say the least. While there have been some reports of successful breeding occurring, the eggs that are laid hardly hatch. Those that don’t normally survive. There could be many reasons for this.

For starters, it could have something to do with the fact that many Red Clawed crabs in captivity are taken from the wild and kept as pets in adulthood, instead of when they are very young. This can lead to undue stress that leads to problems such as infertility in animals.

There is also the added factor that when the crabs give birth to fertile offspring, with the eggs hatching, it isn’t uncommon for the parents to feast on the larvae instead of letting them grow up. With all these factors compounded together, it can be assumed that breeding Red Claw Crabs is nigh impossible.

Since we are already talking about how the crabs eat their larvae, why don’t we move on to the food that they need in order to survive? Red Claw crabs are, for the most part, predators and hunters, unlike most other crab species which tend to be scavengers. Despite the fact that they tend to hunt their food, they are omnivorous in nature, similar to prehistoric humans.

This means they also spend a good amount of time in the wild foraging as well as hunting. They aren’t particularly picky with their food either, eating whatever it is that you choose to give them. It is recommended that you feed them, as well as all pets, a varied diet that consists of different kinds of native protein and vegetables.

They particularly enjoy brine shrimp, bloodworms, pieces of raw fish, peas, leafy greens, or spinach-provided that none of it is seasoned. Before you feed your Red Claw Crab anything though, make sure you check for specific proteins that may be harmful.

One of these proteins to look out for is Thiaminase. If your Red Claw Crab gets too much Thiaminase in their diet, they may get sick due to how Thiaminase blocks the metabolism of the protein Thiamine. This lack of absorption can lead to many health issues.

On the other side of the spectrum, key nutrients to look out for would be calcium and iodine, which are plentiful in the wild for the Red Claw Crab and help keep their shell and claws strong.

On the topic of claws and shells, shall I share with you common traits that are in the appearance of the Red Claw Crab? As stated multiple times these crabs are very eye-catching. Their bright red claws, which contrast immensely against their rather mutely colored bodies, make them a sight for sore eyes.

Red Claw Crab Appearance
Red Claw Crab Appearance

Most often these dully colored crabs will have spots polka-dotting their body, this allows them to camouflage rather easily in their native habitat. Allowing them to avoid predators from above that might be looking for a tasty (and crunchy) snack. Another notable feature about these cuties is that they have two eyes placed upon long antennae-like stalks.

These eyes allow them to look around them a total of 360 degrees, a much larger range than a human’s 180-degree vision. To add to this somewhat alien-sounding appearance they also have a grand total of ten legs with only eight of them being for actually walking in their sandy environments.

The claws themselves tend to have a fade about them, oftentimes having yellow or orange mixed in with that famous red.

There are some subtle variations between males and females, like in most species. Not only are their undersides different, like with all crabs, but males will tend to have more vivid and thicker claws. This vividness can witness the best in just how much color they have with males practically glowing with how many colors they have on those pincers of theirs.

Red Claw Crab Size
Red Claw Crab Size

Now some may wonder how big is this crab actually? Well, I can tell you they certainly aren’t the largest of crab. They can have a leg span of up to 4″ (10 cm) and a carapace usually of no more than 2″ (5 cm). In this way, you can see that the Red Claw Crab is dwarfed by other well-known crabs such as the Alaskan Snow Crab and the Blue Crab.

With all this knowledge under your belt, you may think that you can just leave a crab in a freshwater tank and then sit back and relax and enjoy the sight of such a beautiful crustacean. Maybe pop a few pieces of raw fish in there that don’t have that much Thiaminase. but have a lot of protein, and call it a day. Well, you’d be sorely mistaken.

As easy as I have, perhaps, made it sound Red Claw Crabs are hardly that easy to take care of. They need daily monitoring and their enclosures need to be carefully constructed with no detail overlooked. If you are hoping to really see the animal thrive, you will need to ensure that the crab feels as comfortable as possible, which means a trip down full proper care is a requirement.

Let’s start with tank size. In my opinion, you should use less of what I call ’fish logic’ and more of what I call ’reptile logic’ when it comes to tank size. What this means is that you want to take into account how much the species travels in the wild more so than how much the species won’t travel in captivity.

Reptiles are prone to moving large distances in order to hunt for food, think Ball Pythons and Garter Snakes. Most fish won’t find a need to do this in captivity, so they won’t. However, since the Red Claw Crab isn’t a food-motivated species, being more motivated over land and territory, that isn’t the case. You can’t just give them food and expect them to become complacent.

Instead, they like to wander around and lay claim to their land. As such it is recommended that you have a tank that can hold between five and ten gallons, with ten being the stronger recommendation. Of course, you can always go bigger than ten but it is a good standard to think of for now.

A ten-gallon tank should be more than enough space for one male and a few females to live together pleasantly. If you can have a tank that allows for both land and water ecosystems then that is ideal. A nicely sized enclosure, however, is not all that you need. You also need to make sure that the water is just like.

Similar to Beta fish, Red Claw Crabs are very picky when it comes to what water they choose to thrive in. In order to understand what type of water they find to be the most comfortable, we need to look at how they live in the wild.

Ordinarily, the water that you find Red Claw Crabs in is shallow and brackish, which means that you may have to replicate this in your aquarium. Your water should also be slightly alkaline as it can also be found in swamps and estuaries.

Now you may be wondering how in the world do you get Brackish Water? Do you collect it? No, you don’t. And please don’t try to collect brackish water for your tank. It can have some nasty parasites in it. As a matter of fact, you can make brackish water at home!

Simply add 1 -2 tablespoons of marine salt to a gallon of freshwater, then mix until it is dissolved completely, and there you go. You have a gallon of brackish water. Simply upscale this to fit your 10+ gallon tank.

The total amount of salt needed in a 10-gallon tank would be about 10-20 tablespoons of marine salt. Make sure it’s marine salt, as iodized salt (or any other kind of salt) will not dissolve properly and will only make your crab sick.

Some other things to keep in mind are water temperature pH levels, and water hardness. The temperature should be between 70 F (21 C) and 88 F (31 C) with the ideal being the median of the two. 79 F (26 C). The hardness of the water should be between 8 and 25 dGH and the pH levels should fall between 7.5 and 8.5 on the scale.

As you can see, the water itself is very demanding for this rather tiny species of crab, and it may be hard to find anything else that’ll thrive alongside them.

Enough of all this tough to understand science stuff. Let’s take a break from all that and talk about the decorum, shall we? Setting up the actual aesthetic of the tank is the most fun of bringing in any new pet into your home. Just remember that these crabs need land and water in order to thrive to the best of their ability, with the ratio being 3 parts water and 1 part land.

By putting in some chunks of land, the crab will be able to relax and feel comfortable, hopefully in small amounts of concentrated light. The first step to any good enclosure for any terrarium-based animal is the substrate. These crabs prefer sandy floors, so start there. The sand substrate will allow them to dig. burrow, and scavenge.

Not only that but their legs are practically built to walk across sandy floors. Another benefit to the sand substrate is that if they ingest any of it on accident, it won’t make them sick via impaction.

If you don’t have a tank that doesn’t have landmasses (paludariums usually have built-in shelves but they can be a bit expensive) then you can make some by using floating objects such as small pieces of wood. You can also make some landmasses by observing how it is done in nature and replicating it, similarly to a shoreline.

If you aren’t particularly skilled in building stuff, however, then driftwood and rocks are as good of an option as any. Just make sure that if you are taking these items from the wild that they are sterilized first you don’t want to potentially get your crab sick.

Not only is driftwood and a few rocks good for when the crab gets frightened and wants to hide, it’ll also aid them when they need to molt.

You may be thinking that plants are probably good to add in there too, but I’d second guess that if I were you. Unless you find plants that’ll grow quickly and that the crab can eat. doing so may not be smart as the crab’s claws are known to uproot plants and rip them to shreds. If the plant flourishes that way, then by all means, but otherwise consider other alternatives to plants.

You can always opt for silk plants, as they are cheaper and do not leave too many particles in the water for your filter to take care of.

Speaking of filtration, a marine filtration system is a necessity. If you wish to go with an environmentally safe option than the normal carbon filters in most pet stores, then please consider one that can be ‘charged’ and reused over and over again in rotation. One option that uses harmless bacteria over potentially harmful and wasteful carbon is floss, cut to size for the filter, with purigen.

These cartridges can be ‘recharged’ so to speak every month (soaking them in a 50/50 water-bleach solution and then soaking them for 24 hours in de-chlorinated water) and swapped out in rotation, thus becoming more cost-effective and better for the environment. No matter what filtration system you choose to use, you will need to do a 10% water change regularly, every week if possible.

In order to do the water change properly, it is recommended you get a siphon. Why? Well because all the clean water will most likely be at the top of the tank, with the dirty water being at the bottom. As such you need to remove the dirtiest water from the bottom while leaving the cleanest water at the top.

Just make sure that your crabs are clear when you do this, you don’t want to frighten them by sticking a hose in their substrate. Now on top of the tank, you’re going to want a very strong lid, one that latches specifically. Because of the curiosity and territory-driven nature of these crabs, they may try to get out of their enclosure.

This can be problematic as only an hour without water could lead to dehydration and even death!
To continue on the grim death subject train, let’s talk about the possible diseases that the Red Claw Crab can contract. There is a bit of good news, and some bad news, as to be expected. On the good side, they are extremely resilient against disease.

They have been observed scavenging on diseased fish without any adverse side effects. Despite this, they can experience vitamin deficiencies, fungal infections, and bacterial infections. Thankfully, many of these issues can be resolved with the proper treatment and are rather easily avoided by taking proper care of them.

It is worth noting though that overcrowding and stress, similarly to with any living organism, can cause the rate at which the Red Claw Crab grows ill to increase. Regular water changes, ensuring that all crabs are comfortable, and a proper diet should, for the most part, prevent or cure most illnesses that the crabs may face in their lives.

In terms of living, the crabs live very interesting lives. That is! if they let you observe them. The Red Claw Crab is a nocturnal species, so unless you are a night owl, don’t expect to see them wandering around exploring. During the day they tend to hide, resting away until the sun sets, that’s when they come out to play or really explore and set territorial boundaries.

At first, they may not emerge from their hiding spots at night, but after enough time growing accustomed to the enclosure, and to you, they should begin to exhibit more curious behavior. If you watch them at night you’ll be able to watch them burrow around in the substrate, scavenge for food, or show off their more aggressive colors.

Be careful as if they feel a crab, fish, or even a human, is encroaching on their space they may grow hostile. Up those claws go and they’ll either attack, leading to a loud bonk on the glass, or go into hiding. They are known to kill tank mates that aren’t the same species as them, so be careful what you put into the tank. All part of the territorial aspect of their species I suppose.

On the topic of Red Claw Crab Tank Mates, we must explain one thing. These crabs should only be cohabitating with other individuals of their species.

Not only because they are extremely territorial, but because of the fact that their tank requirements make it very hard for them to have suitable tank mates that can survive their entire life not only running from such an aggressive crab but also just living in the brackish water.

If you do choose to have fish in the tank that isn’t other Red Claw Crabs, then you need fast swimmers who can thrive in brackish water and tend to stick to the top of the water instead of going down into the depths. Mollies, Flagfish, and larger Gobies tend to do the best here, just remember you need a land section so underwater exclusive species may struggle.

If you really don’t want to have your Red Claw crab be lonely, then just pair it up with other Red Claw crabs. So long as there is at max one male per tank, this should be fine. Having more than one male will cause them to fight and leave only one male left. This can happen with females too, but having just two should keep them from doing so.

It is recommended you have just one male and either one or two females to avoid aggressive behavior. If your tank has more than enough hiding spots then each crab will have their own section to relax, thusly allowing them to keep to themselves without all the fighting. They each have their own territory, and that’s all that matters.

Red Claw Crab is a lovely pet
Red Claw Crab is a lovely pet

In conclusion, the Red Claw Crab is a lovely pet for the more experienced fish keepers. So long as you keep all of this in mind then you will be able to care for this species with ease.

If you have any questions feel free to leave a comment. So tell me, do you think you would like to care for this species? I personally will stick to my more docile reptiles and axolotls! A lot less bright red claws flying that way!

About Rencel Leyran