Red claw crabs are fascinating pets that can live happily in a tank or aquarium at home. With their bright colors active nature, and quirky behaviors they are fun and interesting to observe. However, sometimes red claw crab owners notice their crabs acting strangely and spending time upside down. This unusual posture can be alarming if you don’t understand the reason behind it.
Reasons Why Red Claw Crabs Go Upside Down
There are a few common reasons why your red claw crab may end up upside down in its tank
Molting
One of the most common reasons for odd crab behaviors like going upside down is molting. Red claw crabs need to shed their exoskeleton periodically in order to grow. The molting process leaves them vulnerable until their new shell hardens. An upside down crab may be getting ready to molt or recovering after a recent molt.
During pre-molt, the crab extracts calcium from its old shell, making it weaker. This lets the crab more easily back out of the shell when it is time to molt. The weakened shell can make it harder for the crab to keep its balance, causing it to accidentally tip over.
After molting, the new soft shell needs 1-2 days to fully harden and gain its normal strength and rigidity. The crab will be clumsy and slow moving as the new shell hardens. An awkward, upside down posture is common as the crab tries to right itself with its soft new exoskeleton.
Surface Issues
Sometimes the surface of the tank or habitat can cause issues that lead to an upside down crab. Gravel substrate that is too loose or smooth can make it hard for a red claw crab to get good traction to stay upright. Similarly, algae growth on decorations and tank walls creates slippery spots.
Uneven or unstable decor like rocks, logs, and plants can also cause crabs to accidentally tip over if they can’t get a solid grip. And if the water level is too high with minimal decor poking above the surface, the crabs may struggle to find a good spot to perch securely.
Illness or Weakness
An underlying health issue can also potentially lead to upside down crabs. Problems like limb loss, molting complications, bacterial infections, parasites, and even old age can weaken a crab. A weak crab is more likely to end up in an upside down position accidentally due to poor coordination or muscle control.
Unfortunately, being stuck upside down for long periods can further exacerbate weakness in a sick crab. Blood and fluids pool in their inverted limbs and organs instead of circulating normally. Over hours or days, this can starve tissues of oxygen and further impair the crab.
Normal Behavior
Sometimes red claw crabs may simply flip themselves over intentionally and hang out upside down for a while. This is totally normal behavior, especially in young, healthy, active crabs.
Red claw crabs use their paddle-shaped back legs to groom themselves and pick food out from under their shell. To reach all areas with their legs, they need to contort into some strange positions, including flipping upside down. It lets them flexibly clean and scratch their entire body.
Red claw crabs also flip over to right themselves if they do accidentally fall upside down. After struggling to get upright again, they may need to take a rest break in the upside down posture before trying again. This is normal and doesn’t necessarily indicate any health problem.
What to Do About an Upside Down Red Claw Crab
So if you notice your red claw crab spending time upside down in its enclosure, don’t panic right away. Take a closer look at the situation to determine the likely cause before intervening:
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First assess if the posture seems intentional or accidental. Watch the crab’s movements and efforts to right itself. Clumsiness likely indicates molting or weakness.
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Check for signs of imminent molting like opaque whitish bands on the limbs or reduced appetite. Also look for a cast-off old shell which confirms a recent molt.
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Inspect the tank/aquarium setup and decor. Remove any loose substrate and scrub algae off slippery surfaces. Stabilize decor and adjust the water level as needed.
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Monitor water quality and tank mates closely. Isolate the crab if aggressive tank mates could be harassing it and causing it to flip.
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Consider supplemental feeding and 30-50% water changes to improve water cleanliness and nutrition. This supports molting and overall health.
Only after determining the likely cause should you intervene directly:
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Gently flip an accidentally upside down crab right-side up. But let an intentionally upside down crab be.
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Avoid handling crabs for a few days before/after molting since their shells are fragile.
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Move pre-molt crabs to an isolation tank with soft sand substrate if they are struggling to stay upright.
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Consult an exotic vet for persistent weakness/illness after improving husbandry and nutrition. Medication or supplements may help.
With close observation and a few adjustments to care, an upside down red claw crab can usually recover well whether due to molting, illness, or just silly crab antics. Only very rarely does an upside down posture indicate imminent death in an otherwise healthy crab. Don’t panic, stay observant of your crab’s behaviors, and make thoughtful changes to get your red claw crab scuttling happily again soon!
Red Claw Crab – Care sheet
I’ve tried to put together a little information about Red Claw Crabs and how to care for them.
Common names: Red Claw Crab, Mangrove Crab, Red Crab
Scientific name: (Peri)sesarma bidens
Temperature preference: ~25 degrees Celsius
I’ve found 3 websites and they all listed different temperature ranges: 21-29, 24-27, 22-25. My crabs seem to be thriving at a temperature of about 24-25 degrees Celsius.
Water hardness: 20 DgH
pH: 7.5 – 8.2 (neutral)
Water type: freshwater or brackish
There is some disagreement among crab fans right now about whether or not red claw crabs need brackish water to live. In nature, they are usually found in areas where a freshwater river runs into an ocean or sea. Because these places have both fresh and salt water, which is called “brackish,” red claw crabs are thought to be able to live there best.
This is what I think about the issue. Most crabs that we are buying from the pet stores are kept in fresh water. They were also bread in captivity, maybe in brackish water but maybe not. The worker at the pet store told me that the crabs I bought had been there (in fresh water) for at least two to three months. I thought they were used to that kind of environment, and I didn’t want to add to their stress by making them get used to brackish water.
Origin: Thailand, Hong Kong, Singapore
Lifespan: ~4 years
Breeding: It is apparently very difficult to breed these kinds of crabs. But if the conditions are right, the female crab will carry bright red eggs inside her. After a few weeks, the eggs will lose their color and turn gray. She should be moved to a different tank at this point because she is ready to lay eggs.
Here is an article by someone who has successfully bred these crabs.
Diet: omnivorous
Can eat anything from fish and shrimp to plants and vegetables. As a staple food I chose sinking pellets made for crabs and lobsters. Occasionally I feed dried shrimp, baby carrots, and lettuce. I also plan to introduce broccoli in the future.
Substrate: preferably sand because they like to burrow. Gravel is okay too but a bare bottom tank is not recommended.
Dry area: It is crucial that the crabs have a dry area that they can climb up on. They are aquatic animals that spend most of their time in water, but they like to dry off every once in a while.
I like feeding them on land, especially pellets that get mushy fast and make the water dirty.
Crabs experience a phenomenon called “Creeping Death”. When this happens they may go stiff, flip over on their back, sometimes they drop legs and claws. Most likely, the crab will die after going through this, but some lucky ones bounce back. This might not happen if they have the right habitat, but no one knows for sure what causes it.
A very important thing I need to mention is keeping the water clean. This goes for any aquatic creatures, not just crabs. Animals that live in water need their water to always be as clean as possible, just like people who live in dirty places are more likely to get sick.
my crab is hanging upside down
FAQ
Can crabs live upside down?
How much water does a red claw crab need?
Do red claw crabs legs grow back?
Do red claw crabs need water changes?
Red claw crabs require regular water changes to maintain optimal conditions. Aim for a partial water change of 25% every two weeks to remove any accumulated toxins or waste.
How does a Red Claw Crab molt?
Red claw crabs periodically shed their exoskeletons through a process called molting. During this time, they may appear inactive or hide more frequently. It’s important to provide them with extra hiding places and avoid disturbing them during the molting process.
Do Red Claw Crabs overpopulate?
Red Claw Crabs have the potential to rapidly reproduce, leading to overpopulation if not carefully managed. To prevent overcrowding in your tank, it is crucial to practice responsible aquarium management and take necessary precautions. One effective method of preventing overpopulation is to introduce a male crab to the tank only during the breeding season.
Do red claw crabs get sick?
Overcrowding and stress have been known to increase the chances of disease in Red Claw Crabs, so make sure to keep these creatures comfortable. Regular water changes and heavy monitoring of water conditions can help you avoid illness as well. Red Claw Crabs can be quite predatory.