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, red claw crab owners often notice their crabs acting strangely and spending time upside down. This unusual posture can be alarming if you don’t understand the reasons behind it.
Common Causes for Upside Down Red Claw Crabs
There are a few common reasons why your red claw crab may end up upside down in its tank
Molting
Molting is one of the most frequent explanations for odd crab behaviors like going upside down, 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, weakening it. This allows the crab to more easily back out of the shell when it’s time to molt. The weakened shell can make it harder for the crab to keep its balance, causing accidental tipping.
After molting, the new soft shell requires 1-2 days to fully harden and gain normal strength and rigidity. The crab will be clumsy and slow moving as the shell hardens. An awkward, upside down posture is common as the crab tries to right itself with its soft new exoskeleton.
Tank Surface Issues
Sometimes the surface of the tank or habitat can cause problems that lead to an upside down crab. Loose or smooth gravel substrate can make it hard for a red claw crab to get 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 potentially lead to upside down crabs as well. Problems like limb loss, molting complications, infections, parasites, and even old age can weaken a crab. A weak crab is more prone to end up upside down accidentally due to poor coordination or muscle control.
Unfortunately, being inverted for long periods can worsen weakness in a sick crab. Blood and fluids pool in their upside down 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, they contort into 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 fall upside down accidentally. After struggling to get upright again, they may rest in the upside down posture before trying again. This is normal and doesn’t indicate a health problem.
What to Do About an Upside Down Red Claw Crab
If you notice your red claw crab spending time upside down, don’t panic right away. First assess the likely cause before intervening:
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Observe the crab’s movements and efforts to right itself. Clumsiness indicates molting or weakness.
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Check for signs of imminent molting like opaque bands on limbs or reduced appetite. Look for a cast-off old shell confirming a recent molt.
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Inspect the tank setup and decor. Remove 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.
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Consider supplemental feeding and partial water changes to support molting and 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 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 care adjustments, an upside down red claw crab can usually recover well whether due to molting, illness, or silly crab antics. Only very rarely does an upside down posture signal imminent death in an otherwise healthy crab. Stay observant of your crab’s behaviors and make thoughtful changes to get your red claw crab scuttling happily again soon!
Frequently Asked Questions About Upside Down Red Claw Crabs
Can crabs live upside down?
Studies estimate around 10% of breeding crabs may die each year after becoming stranded upside down on beaches, pushed by waves. Horseshoe crabs can survive upside down as long as their gills stay wet, but sunlight can quickly dry out and kill them.
How much water does a red claw crab need?
Most likely a 5-20 gallon tank will be appropriate, depending on the size and number of crabs. An overcrowded tank can cause stress and disease.
Do red claw crabs’ legs grow back?
Yes, crabs can regenerate lost limbs after a period of time, so declawing is seen as more sustainable than taking the whole crab.
Do red claw crabs need water changes?
Yes, partial 25% water changes every 2 weeks remove accumulated toxins and waste.
How does a red claw crab molt?
They periodically shed their exoskeletons. During this time they may seem inactive or hide more. Provide extra hiding spots and avoid disturbing them while molting.
Do red claw crabs overpopulate?
They can rapidly reproduce, leading to overcrowding if not carefully managed. Prevent this by only introducing a male during breeding season.
Do red claw crabs get sick?
Overcrowding and stress increase disease risk. Regular water changes and monitoring help avoid illness. They can also be quite predatory.
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 currently exists some controversy among crab enthusiasts about whether or not red claw crabs need brackish water to survive. In nature, they are usually found in areas where a freshwater river runs into an ocean or sea. Because these areas are a combination of fresh and salt water, aka brackish, it is thought that this is the ideal habitat for a red claw crab.
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 pet store attendant told me that the crabs I had purchased had been in their store (in fresh water) for at least 2-3 months. So I assumed that they were accustomed to that kind of environment and I didn`t want to cause them more stress by making them adjust to brackish water.
Origin: Thailand, Hong Kong, Singapore
Lifespan: ~4 years
Breeding: It is apparently very difficult to breed these kinds of crabs. But when ideal conditions are available the female crab will carry bright-red eggs in her belly which, in a few weeks, will lose their bright pigment and become grey. This is when the female is ready to lay the eggs and she should be moved to a different tank.
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. Although they are aquatic animals and spend most of their time in the water, they like drying up from time to time.
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. It is not certain what causes this, but a proper habitat might be able to prevent it from happening.
A very important thing I need to mention is keeping the water clean. This goes for any aquatic creatures, not just crabs. Just like humans are more susceptible to diseases if they live in a dirty environment, water creatures need their water as clean as possible at all times.