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|
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
One of the best ways to figure out how to keep an animal in captivity is to have a look at what its natural habitat looks like. After all, it has evolved to live there and will benefit from a similar environment in our home!
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.
All 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. This means you’ll need to set up a brackish aquarium if you want to keep them.
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. You don’t need a lot to go brackish: a simple salinity meter and some aquarium salt will get you a pretty long way.
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.
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.
Keep in mind that because red claw crabs need paludariums, the water area will be limited. The actual water volume can be pretty small, so keep that in mind while choosing tankmates. Calculate how much water is actually in your tank before you head out to buy fish.
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!
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