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Caresheet: Red Claw Crab | Perisesarma bidens

June 18, 2015
perisesarma bidens

Red claw crabs are very interesting to keep and a very easy impulse buy, but unfortunately there is still a lot of misinformation about their care to be found in aquarium stores and on the Internet. They are often kept in freshwater community aquariums, but their ideal habitat is actually a single species low-end brackish paludarium!

Keep reading for more information about keeping red claw crabs and setting up a suitable home for them.

Note: Red claw crabs need brackish water. A list of freshwater crabs can be found here.


Tank size 23.5"/60cm paludarium
Temperament Aggressive
Diet Omnivore
Temperature 75-80°F/24-26.5°C
pH 7.5-8.5

Perisesarma bidens, red claw crab, red clawed crab, mini crab. They’re also sometimes still referred to as Sesarma bidens or (Pseudo)sesarma moeschi.

Red claw crab natural habitat

Red claw crabs are naturally found in mangrove swamps in Asia. In these estuaries, rivers flow into the sea, creating a mix of fresh and salt water. The water is quite shallow, temperatures are tropical and the ground is usually covered with fine sand. This gives us some great guidelines for what a red claw crab paludarium should look like!

Red claw crab appearance

With a size of no more than around 4 inches (10cm), red claw crabs stay smaller than some of the other crab species available in aquarium stores, which is why they’re sometimes referred to as “mini crab”. Males are easy to tell apart from females: their characteristic red claws will be larger and the underside of their shell is pointy instead of broad and round.

Red claw crab requirements

As mentioned before, red claw crabs are not fully aquatic and should ideally be housed in at least a 23.5/60cm paludarium with plenty of access to land. They are also not freshwater crabs: water salinity should actually be around 1.005. As with all types of tropical aquarium setups, the water should be heated, filtered and cycled. Water changes should be done regularly. For more information about setting up a brackish aquarium or paludarium (which is actually not as difficult as it sounds), check out this post.

Mimicking the natural habitat of your red claw crabs is quite easy and results in a very beachy looking paludarium. The land area should be sandy. Multiple hiding places are a must because crabs need a quiet place when they are molting and vulnerable. For a realistic effect, you can add rocks, aquarium plants such as Java fern that can withstand brackish water and mangrove ornaments. Real mangrove is possible too, but it’s not the easiest plant to grow and it gets very large.

Important! Red claw crabs are the ultimate aquarium escape artists. When setting up their tank, seal off any and all possible escape routes or you will find your crabs on your floor sooner or later. They dehydrate very quickly, so this can potentially be fatal. The water line should never be up to the rim of the tank, keep openings for filter/heater cords as small as possible and avoid placing decorations in a way that allows the crabs to climb all the way to the top of the tank.


DSC02185 by captkodak on Flickr.

Red claw crab tankmates

When choosing red claw crabs it’s very important to try to avoid getting multiple males, as territorial fights are not uncommon and can sometimes result in injury or death. In a 23.5″/60cm paludarium, 1 male and 2 females or 3 females should work well. It’s easiest to keep your red claw crabs in a single species setup, but if your water area is large enough it is possible to keep additional tankmates.

When choosing, keep in mind that crabs do hunt fish, especially when they’re slow or sick. Tankmates that can withstand low-end brackish water and aren’t bottom dwellers, such as guppies, should be able to avoid any nippy claws.

Red claw crab diet

Although red claw crabs do actively hunt, they are not strict carnivores. A healthy red claw crab diet should include plenty of proteins such as bloodworms and small pieces of uncooked fish or prawn. This should be supplemented with veggies like leafy greens, peas and spinach. Red claw crabs will usually also eat regular fish food, algae pellets and commercial crab foods like Hikari crab cuisine, which should help supply them with enough calcium to grow and molt succesfully.

Red claw crab behavior

Although they do spend a portion of their time hiding, especially when molting or scared, these crabs are very fun to watch and interesting to keep once they come out. If you use a soil substrate you’ll see your crabs displaying their natural scavenging behavior for most of the day. When they encounter another crab or a fish they will usually get defensive, raising their claws and chasing the intruder away.

Some aquarists report their crabs getting used to them and losing their fear after a while. However, if you ever have to handle your red claw crab for any reason don’t forget that they will still pinch hard enough to startle you!

Red-clawed crab

Red-clawed crab by Björn König

Breeding red claw crab

Breeding red claw crabs is unfortunately very challenging and virtually impossible to do at home. Similar to some other invertebrate species like Amano shrimp, red claw crabs start their lives as larvae and will likely not survive in your aquarium. Females will often carry eggs, but these don’t hatch or the young die off almost instantly.

If you have any more questions about keeping red claw crabs or if you want to share your own experiences, be sure to leave a comment below. Happy fishkeeping!

Cover photo: meanandpinchy

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  • Reply Alyssa January 16, 2018 at 4:38 am

    Hi! I have a question. We have our red claw crab set up with a “beach” and a large shop ornament to hide in. He liked it for a few days, but no he has stopped moving much. We have only had him for a week, and I’m concerned about temp. I have a water heater but it’s still only at 72. I have another on the way by mail because the store didn’t offer a large range.

    But my main question, is do they need the air temp to be 75 F as well? I live in a northern climate and the house temp is currently at 69 F. Could this cause lethargia?

    Thank you!

    • Reply Mari January 19, 2018 at 5:46 pm

      Hi! I’d expect things to improve temperature-wise once you get the new heater and can get the water temp up a bit. Obviously that will also raise the air temp a bit to what is probably an acceptable level.

      As for inverts and lethargia – it can also be related to molting, which can cause issues especially with new crabs. They don’t always receive proper care at the aquarium store and as a result are sometimes too weak/nutrient depleted to molt properly. In any case, it’s normal for them to remain in hiding for a while when they’re attempting to molt. If it really is molting there isn’t much you can do, it either works out or it doesn’t.

      Finally – did you cycle the tank before getting the crab? The water area should be cycled properly like any other aquarium. Have you performed a water test with a liquid test kit to check whether the water values are still where they should be?

      I hope the crab is doing better by now! Good luck.

  • Reply Jeanna December 18, 2017 at 4:06 am

    Hi Mari! I’ve never had a crab before, but I’m in a marine biology class and I came across these crabs for a project I was working on, they seem cute so I was interested in getting two or three! I read everything extensively and I have some questions to ask, I don’t want this to be an impulse buy and I really want to know how to care for the crabs the right way. First, will a 20.2×10.5×12.5 tank be suitable enough for the crabs? Second, how often should I change the water and where should I keep the crabs when I do change it? If I got two male crabs would it be super dangerous to keep them in the same tank? How many ornaments sound I buy and how much sand if I’m using the tank size listed above? I’m sorry if these are a lot of questions, I hope you can answer most of them!

    • Reply Mari December 21, 2017 at 12:00 pm


      Are those measurements in centimeters or inches? If it’s cm that definitely won’t cut it unfortunately, if it’s inched then I think you should be fine. Water changes completely depend on the way you set up the tank, but you usually do a weekly water change based on how much nitrate has built up. There is no need to move the crabs when you change the water, as you won’t replace all of it so they just stay in there.

      I would definitely try to avoid getting two males – you can sex them relatively easily (described in the article). Hide-wise, I’d do at least two caves or other hiding places per crab. As for sand, that also depends on what you want to do with the tank. You’ll need to get enough to provide a nice big land area for the crabs.

      I’m not sure what a marine biology class entails, but just to be sure: don’t forget to cycle the tank, even though the crabs won’t be in the water all the time it should still be filtered and heated.

      Good luck! Nice to hear you’re doing your research 🙂

  • Reply Amir November 15, 2017 at 2:32 am

    Hey i had 3 red claws in a setup but i put plastic walls inbetween and they all somehow climbed into the center area why and how

    • Reply Mari November 22, 2017 at 11:42 am


      As you can read in the article, red claw crabs are very good climbers. I’m not surprised they managed to climb the plastic wall. Why do you have plastic walls in between anyway?

  • Reply Emily June 20, 2017 at 4:07 am

    I have just recently got a crab and it molted not long ago. For a couple days now he’s barely been moving and has been going upside down, a few times I thought he has been dead. I don’t think he’s eaten for a few days and I left for the weekend and when I came back he was upside down in the same spot I left him, yet still moving his claws and mouth (he won’t move his legs). He’s just recently molted about a week ago so I’m not sure if he could be trying to again. It’s been at least four days of not moving anything but his claws. He has also spewed out a black liquid from his mouth, and his belly flap was open at one point (not sure if it’s a male or female but I’m pretty sure female). Do you know what’s going on?

    • Reply Mari June 20, 2017 at 12:10 pm

      Hi! I’m sorry to hear your crab isn’t doing well 🙁 If your water values look normal (have you checked?) and your setup is in order I think you might be dealing with a bad molt here. This can happen when an invertebrate is in bad health and/or has a calcium deficiency. It might not have enough energy to recover or not enough calcium to produce a proper new shell. Besides keeping the water clean and maybe offering food once in a while I don’t think there is much else you can do for now. I hope it recovers!

  • Reply Jesus May 9, 2017 at 7:12 pm

    Hi, I have one red clawed crab, this hasn’t happened yet but what would it mean if a crabs claws start turning a darker color, also I have one of those habitats for hermit crabs, it’s like 2-3 feet long and 1 and 1/2 foot wide, is this a good enough space or should I get it something better

    • Reply Mari May 10, 2017 at 11:08 am

      Hi! I’m not sure about the claw thing, it might have to do with the molting cycle. As for the hermit crab habitat, if it’s just a regular glass tank that can hold water for the aquatic part it should be fine. 🙂

      • Reply Jesus May 10, 2017 at 3:11 pm

        Yeah it can hold water, also how do I keep my water warm, from what I’ve been told these crabs prefer warm water, I’m constantly changing the water to keep it some what warm, or is cool water fine?

        • Reply Mari May 10, 2017 at 3:34 pm

          You use an aquarium heater just as you normally would! If you’re not familiar with maintaining an aquarium it would be a good idea to read up on that a bit. For example, even though red claw crabs don’t spend all of their time in the water the tank should still be fully cycled.

          Good luck!

  • Reply Llama March 24, 2017 at 11:36 am

    Great page very insightful I’ve had 2 red claw crabs for just over a week due to an impulse buy and they are sloop interesting to watch there is very little or contradicting information around the internet on how to care for them but this page is defiantly the best help I could find thank you .
    Going to introduce them to fresh prawn tonight see how they like them

    • Reply Mari March 24, 2017 at 2:06 pm

      Glad it was helpful to you! Good luck with your new crabs. 🙂

  • Reply Kaleb January 24, 2017 at 11:45 pm

    A few questions. Do they breathe in or out of water? Do they need to be fed in or out of water? How often will my crab come out of water and use the beach I’ve made for it?

    • Reply Mari January 26, 2017 at 2:44 pm

      Hi! I think they have gills and can breathe both underwater and out of the water but I’m not entirely sure. You can feed them both underwater and out of the water (also depends on what kind of food you’re giving, whatever is more convenient!). They usually spend around half their time out of the water.

      Hope that helps!

  • Reply Deebs November 21, 2016 at 12:42 am

    My crabs keep dying and I’m really not sure why. The tank is healthy and clean and water is brackish and everything but every crab I got keeps dying :-/

    • Reply Mari November 23, 2016 at 2:48 pm

      I can’t really help you out without more info! Is the tank cycled and what are the water values? What is the salt grade? What does the layout look like?

  • Reply Joe August 30, 2016 at 6:23 pm

    Hey, I want to know if I can have them in a slightly salinated water with some land and house with some crays and turtles

    • Reply Mari August 31, 2016 at 5:58 pm

      Hi! No, crays/crabs and turtles cannot be combined. Crays and crabs can’t either. Sorry!

  • Reply Michael C August 4, 2016 at 11:57 pm

    Why did my female Biden die with her eggs? 🙁 she was perfectly fine but she did turn into a brownish color and lost a claw for some strange reason 🙁 help?

    • Reply Mari August 9, 2016 at 9:50 am

      I can’t tell you much about that without more specific info, sorry! You could try asking on an invertebrate/aquarium forum.

  • Reply Andi June 4, 2016 at 9:50 am

    Is it normal for the crabs to be a sandy color a few days after molting? My female just molted and she is paler than usual, but still very active.

    • Reply Mari June 4, 2016 at 2:05 pm

      I’ve never seen a red claw crab right after molting so I can’t confirm whether a sandy color is normal, but a lighter color in general is definitely normal yes! Their new exoskeleton is still relatively soft and weak.

    • Reply Stephen July 31, 2016 at 6:09 am

      I have a female red claw introduced a male an within the hour she just stopped all movement I can touch her an she moves but it is almost like just a twitch what is this can they go from fine to moltin just in the blink of an eye

      • Reply Mari August 1, 2016 at 11:16 am

        That doesn’t seem like she’s molting. Have you done a water test?

  • Reply kenny May 22, 2016 at 5:57 pm

    hi there, nice website.

    one of my crabs had a big fight and lost his 2 claws, you have anny idea how and what to feef him?
    don’t want to loose him 🙁

    kind regards

    • Reply Mari May 29, 2016 at 7:37 pm

      Sorry about the late reply, I was out of town for a few days. How is the crab doing? Just feed calcium-rich foods. Crabs aren’t supposed to fight so be sure to reassess your setup!

  • Reply blucanary April 9, 2016 at 12:19 pm

    I’m considering getting a thirty gallon tank for a figure 8 puffer, and I’m wondering if these would make good cleaners, as I’ve heard that the puffers get very messy

    • Reply Mari April 9, 2016 at 10:52 pm

      I suggest doing a little more research on the puffer! You’ll find out that their diet consists almost entirely of crustaceans, so not an ideal combo at all 😉 these crabs are also not great cleaners. With puffers and all aquarium fish, the cleaning is ultimately up to you! Vacuuming the bottom of the tank frequently, keeping up with water changes and removing any uneaten foods quickly are the key here. Good luck!

      • Reply blucanary April 10, 2016 at 10:25 am

        aw darn
        i knew that they ate crustaceans, but I keep dwarfs with cherry shrimp w/o too much trouble, and the cherries save me the trouble of cleaning for the most part

        • Reply Mari April 10, 2016 at 10:33 am

          We keep a dwarf puffer with cherry shrimp too, but they really can’t be compared with any of the larger puffer species. None of those can be kept with any tankmates, they’re pretty much killing machines unfortunately haha. :/

          • blucanary April 10, 2016 at 12:31 pm

            oh okay

  • Reply caroline murray March 4, 2016 at 7:22 am

    sorry another question can I keep a lobster or other crabs with the red claws please??

    • Reply Mari March 4, 2016 at 12:43 pm

      Hi! Great to hear you’re thinking about getting some red claw crabs. I’m sorry about the dead link – Fish Girl’s Koi Pond was changed to Fish Girl Writes, you can now find my guest post with all the info you need to set up a brackish paludarium for your red claw crabs here 🙂 it should answer all your questions relating to setting up the tank. Also be sure to have a look at the article about cycling an aquarium, as this has to be done with brackish aquariums as well.

      As for your question about tankmates – that doesn’t sound like a good idea. I don’t know of any peaceful, small brackish crayfish/lobsters and other crabs will surely end up causing trouble. As mentioned in the caresheet, red claw crabs are best suited to a single species setup! If you had a larger tank there would have been some brackish fish species that could work in the aquatic part, but unfortunately for a 60L I would definitely recommend just the crabs. But don’t worry, they provide plenty of action and your tank won’t become boring!

      • Reply caroline murray March 5, 2016 at 8:34 am

        Thanks for all your help and the links were very helpful to I cant wait to get my tank and get it set up. thanks a lot 🙂

  • Reply caroline murray March 4, 2016 at 7:20 am

    Hi thanks for the info sheet I have bought a 60 ltr tank waiting for it to arrive to have it for the red claw crabs. I have a tropical fish tank with fish and have had a marine tank years ago. would like some advise on how to set it up and how long to wait till I get crabs please the link above doesn’t work unfortunately many thanks
    caroline 🙂

  • Reply Kate February 11, 2016 at 6:18 pm

    Thanks for the info. I have a red claw crab which I bought four days ago. He was moving about fine in the tank then once I made access for him to go out of the water on a piece of wood he hasn’t yet come down. He does sometimes go on the side of the wood so gets wet and I’ve put some food up where he is but the wood is only about 2″x2″ and he has just been up there for days. Is this normal? Should I be worried or put him back down into the water?

    • Reply Mari February 13, 2016 at 2:44 pm

      No, there is no need to worry. As mentioned in the caresheet, red claw crabs are not fully aquatic and will spend a lot of time on land. You may actually want to provide a bit more land area! Also, is the water in the tank brackish?

  • Reply Elwood January 5, 2016 at 12:46 am

    Thanks for the info

  • Reply Payton January 4, 2016 at 7:54 pm

    I have a five gallon tank that I am setting up for them I already have a ten gallon tank full of fish I want to set up an old five gallon tank for the crabs how many crabs would be acceptable for this tank

    • Reply Mari January 4, 2016 at 8:52 pm

      As mentioned in the caresheet, 15 gallons is unfortunately the minimum size for red claw crabs! In a five gallon, none would fit.

      • Reply Payton January 5, 2016 at 2:32 am

        I got a 15 gallon tank for the crabs like u said and set it up I fed them lettuce because they were eating my live plant what are som other vegetables I can feed them the crabs screen very happy

  • Reply Elwood December 29, 2015 at 1:23 am

    I am a some what experienced aquarist with two 125 gal and two 55 gal other tropical tanks running. I am also experienced with some salt water years ago.
    I am starting up a tropical crab aquarium . It is a 20 gal. half full of water with 1 table spoon of salt to 5 gal of water. My question is, with such a low water level in the tank how do I create & keep a biological bacteria filter going with out using a under gravel or over the edge box filter? Thank You

    • Reply Mari January 2, 2016 at 3:40 pm

      Sounds like a fun project! You could use a normal internal filter and replace part of the sponge with biological filter material or you could go for an external filter, those have tons of room for biological filter material. You’ll also need to use a bit more salt, maybe around 1 table spoon per five LITERS instead of gallons. Be sure to get a device to measure salinity too!

      • Reply Elwood January 5, 2016 at 12:45 am

        Thanks for the info

      • Reply Julian munoz November 25, 2016 at 10:13 am

        I was wondering if my red clawed crabs can eat a unique blend of pellets, dried shrimp, and mealworms .

        • Reply Mari November 25, 2016 at 11:01 am

          I’m missing the greens here, they’re not carnivores! Veggies like leafy greens and peas should be included in their diet. I’m also not sure how nutritious dried shrimp are, try going for fresh shrimp instead. As for the mealworms, not sure about those honestly! I don’t know enough about them to figure out whether they work well in red claw crab diet.

          Good luck!

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