Being a recent addition to the aquarium hobby, crabs are quickly gaining popularity every year. These astonishing crustaceans have a lot of character, personality, and can be great pets, even for beginners.
Due to every growing need, these FAQs cover the most commonly asked questions hobbyists have on crabs.
General Questions about Crabs
1. Are crabs suitable as pets?
Yes, they are. In my opinion, crabs make fabulous pets for young and old alike.
They are beautiful, exhibit fascinating behaviors, easy to keep and feed. Crabs do not require a lot of attention and maintenance. In addition, they are relatively cheap.
Of course, there are also some downsides that you should be aware of when selecting one. Such as their messy nature, being antisocial, etc.
2. Can you raise crabs at home?
Yes, depending on the species, it is even possible to breed them at home.
3. What are the most common types of pet crabs?
Depending on the habitats, there are several crab species that dominate the pet fancy. The most common types of pet crabs are:
4. What are the best ones to start with?
This is a difficult question to answer because choosing a species is a personal decision. In addition, many beginner hobbyists have their own ideas and preferences about the aquarium, paludarium, or terrarium they would like to have.
Based on this, I would simply recommend starting with the most common and popular types of pet crabs I have already mentioned before.
5. How long can I expect my crab to live?
A crab’s lifespan depends on the species since their life expectancies widely vary. However, if we are talking in general, the average lifespan of pet crabs is 2 – 5 years.
Their life expectancy depends on many factors such as breed variation, feeding, living conditions, shipment stress, etc.
Under optimal conditions and good care, crabs can live a long and happy life.
6. Do veterinarians treat pet crabs?
Unfortunately, unlike many other pets, crabs do not have well-developed veterinary services. As far as I know, crabs are not included in vet school programs and they do not even know how to properly care for them.
Crabs have different physiology. Because of their calcified shell (exoskeleton), there is little anybody can do, when they get sick or infected. Also, crabs do not have blood pressure, so, it is not possible to even take a test.
7. How to tell the difference between a male and a female crab?
It is fairly easy to tell the difference between male and female crabs. All we have to do is to look at the underside (abdomen shape).
Males have a narrow and slimmer plate while females have a broad plate on their belly.
In some crab species, there can be other pointers as well such as:
- general size (males are bigger),
- color differences (males are often more colorful),
- behavioral patterns (males are usually more aggressive),
- claws (males have bigger or asymmetrical claws), etc.
However, keep in mind that many of these traits are only present in mature adults and belong to a particular species.
8. Do crabs sleep?
Yes, sleep is fundamental to all animals including invertebrates and crustaceans such as crabs.
In terms of behavior, sleep is generally characterized by indifference to the outside world. In terms of brain wave activity, sleep is composed of several different stages and is associated with slow waves of electrical activity in the brain.
According to the experiments, crustaceans also exhibit slow waves, as well as the behavioral signs of sleep such as:
- Complete absence of movements.
- Loss control over some part of their body (their antennae often lower down).
Crabs sleep with their eyes open as they have no eyelids.
9. Are crabs nocturnal?
Yes, most crab species are nocturnal creatures. Even though they can also be active during the daytime, experiments show a negative reaction to light intensities corresponding to daylight illumination.
Therefore, the nocturnal habits show the crab’s true nature. For example:
- The true peak of their activity starts at dusk. In the wild, nocturnal behavior is a form of adaptation to avoid visual predators whilst feeding.
- Crabs have compound eyes which allow them to see in the dark.
- Molting, breeding, and mating are usually done at night.
10. Do crabs have a heart?
Yes, many invertebrates, including crustaceans like the crabs, have neurogenic hearts. It means that the heartbeat is received by a nerve impulse coming from a nerve ganglion situated near the heart.
11. Do crabs have brains?
Yes, crabs have a brain located between their eyes. However, this is a very rudimentary ‘brain’ because it consists of nerve cells concentrated in a set of ganglia.
The ganglia interconnect by bundles of nerve fibers that transport the signals at high speed.
Interesting fact: Even though the crab’s brain has some overall control over the animal, some parts of their body are controlled by small nerve clusters at the end of each segment (walking legs, pleopods, etc.). Thus, in some situations, crabs can do quite well even without the brain being present.
12. Do crabs feel pain?
Whether crabs feel pain or not has been a subject of discussions for many years. The main problem here is that definition of pain cannot be fully applied to crabsbecause of their nervous system.
For a long time, scientists presumed that these animals simply reacted mechanically. In other words, there was no implication that central processing and decision-making are involved in responses.
Nonetheless, according to the latest research, it is believed that invertebrates may experience some form of pain.
13. Is boiling crabs alive cruel?
Yes. That is why, to eliminate any chances of inhuman treatment, some countries decided to legislate for crustaceans to be stunned or knocked out before boiling them. This way they won’t feel any possible pain.
14. Do crabs have emotions (feelings)?
There is still ongoing debate about the nature of emotions in animals (especially invertebrates).
15. Are crabs in the lobster family?
Lobsters and crabs share a single evolutionary origin but their evolution separated 500 million years ago.
Lobsters belong to the family Nephropidae and Homaridae. Whereas crabs belong to the infraorder of Brachyura.
Questions about Feeding Crabs
16. What do crabs eat?
Generally, crabs are opportunistic omnivores that can feed on a variety of food items (either living or decomposing) including vegetables, plants, algae, insects, animals and detritus.
Crabs are not fussy eaters. Basically, they will eat just about anything they can get their claws on.
Just keep in mind that, protein and calcium are crucial for growth and calcification.
17. How often should I feed my crabs?
Adult crabs should be fed every day or two to prevent them from starving and picking on tankmates.
Young crabs require more frequent feeding to grow and molt. Therefore, we should feed them every day.
18. How long can a crab go without food?
Crabs are capable of going up without food for a long period of time (1 – 2 weeks). However, it is still not recommended to leave them without food for more than 1 week.
Besides stress, lack of food can have other negative effects on your pet’s overall health such as:
- decreased growth rate,
- molting problems,
- immunity system failure,
- increased aggression,
- cannibalization, etc.
Even though crabs are very hardy animals and some species can survive without food for several weeks, keeping them without food for that long is like pushing your pets to the limit.
Questions about Keeping and Housing Crabs
19. How can I tell if my crab is stressed?
You can tell if your pet crab is stressed by paying close attention to stress-related symptoms. Some of the most common signs include lethargy, strange behavior, decreased appetite, discoloration, decreased growth, and molting problems.
It is important to figure out what is causing them and act immediately. It is important to remember that stress can weaken crab’s immune systems and make them more susceptible to diseases and inhibit their ability to fight illness.
20. How do I keep my crab happy?
Unlike many other pets, crabs do not complain or demand attention. Therefore, it is important to know their natural requirements.
To keep them happy, technically, we need to keep them healthy. For that, we need to give them a healthy proper diet, adequate enclosure, appropriate environment, and tankmates.
21. Can I keep crabs in planted tanks?
I understand that plants can make any tank look more attractive and appealing. However, keeping crabs in planted tanks can be a serious challenge.
The point is that most crab species are very destructive, especially, large species. Do not be surprised when they will eat, cut, and shred every plant they can get.
You need to do your research beforehand!
22. Where should I house my crab?
Appropriate housing is crucial in maintaining a healthy pet. Do not set the tank as a walk-through zone! Your crab will be more comfortable when kept in a quiet place away from the noise, excitement, and other stress factors.
Ideally, their location should be away from direct sunlight, and without sudden environmental changes.
23. Can I add freshwater crabs to my aquarium immediately after purchasing them?
The answer at this point is definitely NO! Aquarium is not just a basin with water.
One major thing to achieve while setting up an aquarium is to make it safe, healthy, and habitable for any aquatic pet — and this is possible only through cycling. Only then can the crabs be added.
24. How big should be crab habitat?
That depends on the size of all the species of crab. For example:
|Species||Tank size (minimum)|
|Thai Micro Crab||5 gallons (~20 liters)|
|Tangerine-head crab||5 gallons (~20 liters)|
|Red Apple Crab||5 gallons (~20 liters)|
|Red Devil crab||5 gallons (~20 liters)|
|Red Mangrove crab||5 gallons (~20 liters)|
|Marble crab||5 gallons (~20 liters)|
|PomPom Crab||5 gallons (~20 liters)|
|Vampire crab||5 gallons (~20 liters)|
|Fiddler crab||10 gallons (~40 liters)|
|Emerald crab||10 gallons (~40 liters)|
|Red claw crab||10 gallons (~40 liters)|
|Halloween Moon Crabs||15 gallons (~60 liters)|
|Sally Lightfoot Crab||15 gallons (~60 liters)|
|Black land crab||15 gallons (~60 liters)|
|Thai Devil Crab||15 gallons (~60 liters)|
|Arrow crab||20 gallons (~80 liters)|
|Panther Crab||20 gallons (~80 liters)|
|Matano Crab||20 gallons (~80 liters)|
|Rainbow Crab||20 gallons (~90 liters|
25. Do crabs clean tanks?
I would not say that crabs can be a good clean up crew. Even though they are a pretty good job at eating the leftover food and decaying plants, crabs are also pretty messy animals.
26. Can freshwater crab live in tap water?
Yes, most crab species are pretty tolerant of poor water quality and can live even in tap water.
Important: The tank should be cycled anyway. Do not add crabs in an uncycled tank. It is also highly recommended that the water in the tank should be free from chlorine and any other harsh chemicals that can be found in most residential tap water.
27. Why do crabs die?
Crabs can die from direct causes such as old age, disease, aggression (fights with tank mates), malnutrition, failed molting, bad water parameters, inappropriate temperate, etc.
In most cases, all these causes are interlinked with each other. For example, lack of nutrition may result in that crab will not store enough calcium in the gastroliths (calcium stones) as a result it may lead to failed molting.
28. Why do crabs go to sleep in ice?
Crabs are cold-blooded animals. It means that their body temperature varies with the temperature of the environment. Their metabolism is directly correlated with the temperature.
Crabs go to sleep because, at low temperatures, all the chemical reactions in crabs slow down until their metabolism just does not work.
29. What would happen if you put a terrestrial crab in freshwater?
Land crabs can stay in water for some time but, eventually, they will drown.
30. Can marine crabs live in freshwater?
No, they can’t. They will die. Marine crabs cannot tolerate freshwater and vice versa.
31. Do freshwater crabs need a filter?
Yes. We need to use a filtration system to keep the aquarium water clean. If there is no filter, water changes should be done more often to control water quality.
Questions about Handling Crabs
32. Can pet crabs be tamed?
No, crabs cannot be tamed in the sense we normally associate with that word.
33. Can I play with my pet crab?
Many hobbyists would love to play with their pet crabs, however, you should not do that!
Remember, crabs do not like to be handled. There are no exceptions. They are not pets you can play with. Do not take them out just because you want to.
34. Do crabs recognize or bond with their owners?
No, they do not.
Crabs are wild animals and are not adapted to living with humans. They are also not capable of bonding with the owner. The best you can get from them is that they may recognize you as a low threat. Everything else is just beyond their abilities.
Strictly speaking, crabs are not smart animals and, generally, operate on their instinctual nature. They do not understand and do not have long-term memory to learn – this is just beyond their abilities and nervous system.
35. Can crabs cut off fingers?
No, crabs can’t cut off fingers. Do not believe it.
Generally, their claws are not sharp and/or strong enough to even break your skin.
Interesting fact: Researchers found out that Coconut crab (Birguslatro) has the strongest grip of any animal. These crabs can squeeze with the force of 1,765 newtons. For comparison, the average human grip is 300 newtons. crocodile jaws. Whereas crocodile jaws can bite down with a whopping 16,000 newtons.
36. How should I handle crab?
The best and safest way to properly hold crabs is to pick them from behind so the claws are facing forward. After that, there are 2 options:
- use your thumb and one finger to put on either side of the crab’s shell.
- put your index finger on top of the crab and slip your thumb underneath the back end of the crab and place it on the abdomen.
Be gentle. Do not squeeze your fingers, it can harm the crab. You should NEVER pick crabs by the claws and legs!
37. Why do crabs rip their own arms off?
Crabs can lose limbs by autotomy. This is a reflexive voluntary removal of body parts by the animal caused either by stress or a predator threat.
Losing legs or claws is pretty normal in the crab’s world because they can always regrow it via molting.
Questions about Compatibility with Tankmates
38. Does my crab need a friend?
Generally, crabs are territorial creatures and do not exhibit social behavior. Their ‘social phases’ are usually restricted to interactions only during mating.
In any case, you have to decide if you have the room to properly care for your pets.
39. Do crabs get lonely?
No, the absolute majority species of crabs do not get lonely, even if it might seem otherwise. Crabs are solitary animals and, as such, they do not mind living alone at all.
It may sound funny, but only hermit crabs are actually quite sociable and enjoy the company.
40. Can I keep several crabs together?
It depends on the species and the size of their enclosure. Multiple crabs can be kept together as there is plenty of room for each crab.
For most species, it is strongly recommended to keep only one male with multiple females. Male crabs rarely can be kept together because they will fight with each other.
41. Can crabs live with crayfish?
No, it is strongly not recommended to keep crabs and crayfish in the same tank. These animals have the same temperament, many species are aggressive and territorial. Therefore, they are not recommended to keep together.
42. How do you stop crabs from fighting?
I need to say right from the beginning that it is not possible to completely eliminate their aggressive behavior. However, there are several ways to reduce it:
- One way is simply to get a bigger tank with A LOT of hiding places. This is the key factor of their survival. It can be all types of leaves, rocks, wood, plants, PVC pipes, and other decorations to enrich the environment in your tank.
- Keep your crabs well-fed all the time. Do not make them hungry. Otherwise, it will increase their aggression and cannibalization.
- If it is possible, do not keep males together.
43. Can crabs live with dwarf frogs?
Generally, frogs and crabs are not compatible.
Most frog species have very sensitive porous skin. There is a very high chance that crabs can damage it. As a result, it may lead to bacterial infections which are often deadly for frogs. In addition, large crabs will try to eat small frogs.
Note: Some frogs species can be too aggressive as well. For example, African Clawed Frogs are strong enough to pull off the legs and claws of the crabs.
44. What are the best crab tank mates?
It is not possible to predict their compatibility without knowing the crab species.
For that, I strongly recommend reading my article “Aquarium Crabs and Tankmates. Possible or Not?”.
45. Can I keep crab with Puffer fish?
Absolutely not! It is not possible to keep them together because their natural diet consists mostly of snails, invertebrates (shrimp, crayfish, crab), and insects.
Hard shell will not save the crab. Actually, it will help Puffer fish to keep their constantly growing teeth short.
Questions about Molting and Behavior of Crabs
46. Why Do Crabs Make Bubbles?
Crabs make bubbles at the mouth for several reasons. They do this to protect their gills against dehydration when their gills expel carbon dioxide, or as a defensive mechanism to avoid predation.
47. How do crabs grow?
Crabs have external exoskeletons (shells) that limit their growth. Therefore, to grow in size, they have to shed their old shells. The process of replacing the exoskeleton is often called molting.
Molting is an inherent cyclic process that occurs in all crustaceans and consists of 4 phases:
48. Do crabs eat their old shell?
Yes, crabs usually eat their old shell later. They will consume the entire exoskeleton to recycle necessary minerals and salts to aid in the calcification process.
49. Why has my crab lost its color?
There can be many reasons why crab can lose its color. For example, stress factors, poor water quality, age (too young), malnutrition, before molting, poor genetics, etc.
50. Why do crabs hide after molting?
During the early post-molting stage crabs need to hide because they are too soft to protect themselves and thus may be more vulnerable to bacteria, viruses, or predators.
This is by far the most dangerous stage for the crabs in their life.