Rainbow Crab

Rainbow Crab 2021: The Complete Guide to Rainbow Crabs Care

Rainbow Crab

Rainbow crab are attractive pets because they are not watery at all, so you can enjoy both in the water and on the ground!

They are also impressive to look at, with their bright colors and eyes that look like glasses.

Although rainbow crabs are not very difficult to care for, they do need to have a dedicated tank and will need a paludarium or a tank that contains both aquatic and terrestrial elements.

We have compiled all the information you will need to properly care for your rainbow crabs. We’ll cover things like behavior, optimal tank conditions, diet, and much more.

Care level:Easy-Medium
Color form:Violet-blue carapace and orange-red legs
Life expectancy:Up to 8 years
Size:3-4 inches (7-12 cm)
Minimum tank size:20 gallons (for a single crab)
Tank configuration:Paludario
Compatibility:Not compatible with other species


In its shape, the rainbow crab represents a group of decapod crustaceans. But the color is unusual, bright and attractive. The shell is painted dark blue (for some people it is purple), the legs are red or orange, the large claws are usually gray, but they are also bluish. The crab’s belly is generally pale white, sometimes with blue stripes. The size of each person can be up to 20 cm wide.

Such a palette of colors and shades has contributed to the existence of many words. According to scientific classification, this crab.

  • in Latin it is called cardisoma armatum,
  • in English-speaking countries, it is called indigo crab (indigo crab), Patriot crab (patriot crab), tricolor or red, blue, land crab (tricolor crab),
  • Due to the fact that this crustacean mainly leads to the terrestrial life form, it is also known as a land crab.

Place in the animal world.

In fact, Cardisoma armatum spends most of its life on land. The range of this species is small: the coastal strip of some islands in the western part of the Pacific Ocean.

In the sandy soil, the crab digs holes, which serve as a refuge and resting place. Near this refuge, he spends most of his life looking for food.

If you are not nearby, the multi-colored arthropod is happily sent looking for food in the nearest thicket. You can be sure: there you will definitely find something to feed.

But incidents sometimes occur when, on returning to his sandy house, the “traveler” finds it occupied by another member of the species. Indeed, why would an invader dig a hole if it finds one already prepared?

In this case, the showdown will certainly begin, and victory does not always go to the true master of the house. Well, in this case, our rainbow crab will go away and skillfully dig up a new house. Even better than before!

But in brackish ocean water this animal rarely enters. This happens only during the mating season and during molting. However, in fresh water, it feels great, which allowed some scientists to consider that the rainbow crab is not only land, but also fresh water.

Sexual characteristics are mild, but experts determine sex by the appearance of the abdomen, the back of the abdomen. When smaller in males, it is much wider for women and resembles a heavy triangle in shape. Also, women tend to be larger than men.

Home conditions

These conditions cannot be called simple, since for the life of Cardisoma armatum in captivity, it is necessary to equip the aquaterrarium. What does this mean?

Home improvement. For the optimal content of the rainbow crab in a normal aquarium, 2 zones are arranged: water and coastal zone. This simulates the conditions of the natural habitat.

The glass container can be shallow, as the water portion fills to a level of 12 to 15 cm. Zoning can be the same (the zones are roughly equal in area) or with the advantage of water coverage.

Some owners of these arthropods fill the entire aquarium with 10 cm of water with the arrangement of stone hills protruding from the surface.

That is why the optimal interior is a sandy land area, fenced off by a water stone ridge (to avoid coastal erosion).

Sand should be a large fraction, it can also be used as a small stone, shell or small gravel. If you pour fine-grained river sand into the aquaterrarium, then with periodic cleaning of the soil, it will go to the siphon.

There are many examples when a piece of pipe, the diameter of which is slightly larger than the size of the crab, is driven into the ground at an angle of 45 °. It is funny to see how an animal climbs there, captures the soil that has accumulated underneath and, pressing it against the body with its claw, brings it to the surface.

Microclimate . In principle, a good aquarium is not an easy construction since the water in the “wet” zone must be constantly cleaned and heated up to +25 degrees (deviation in one direction or another is not allowed more than 2 ° C).

In addition, there should be a constant temperature in the aquaterrarium in the range of + 25 ° C to + 28 ° C. The equilibrium level of the pH should be kept at a neutral level, and the hardness may increase, but not more than 20 °.

You must constantly monitor the purity of the water, which is achieved by a filter. At the low water level indicated, an internal or external filter of medium or low power will be adequate, but it must necessarily have a biological filtration stage. The fact is that Cardisoma armatum does not tolerate an increased concentration of nitrogen-containing compounds in water (nitrites and nitrates). In addition to biofiltration to reduce the dose of harmful substances once a week, they organize a water change for about 1/5 of the total capacity.

The vegetation . As for soil plants, on land they will be dug up with a 100% probability. In this regard, if there is a desire to plant trees in the aquaterrarium, it is better to install potted greenery.

Aquatic plants are quite appropriate. They will not only serve as decorations, but they will become food for a colorful crustacean. Experts recommend planting moss, elodea, or Javanese horn poles in water.

Behavior and compatibility

The shape of the rainbow crab is complex, difficult. If the aquaterrarium contains two or more individuals of this species, then conflicts over the territory may arise.

As a general rule, battles do not begin immediately, escalation of tension occurs gradually. At first there may be attempts to capture the mink, then the rivals will try to remove the food and only then can the fight begin. However, the matter does not reach serious battles.

To avoid conflict situations, some owners of multiple rainbow creatures organize a separate dry zone for each occupant of the aquaterrarium. In this case, take into account that an animal requires at least 0.4 m² of its own territory.

In water, Cardisoma armatum is found during molting. In puppies, it occurs 1 time in 10 days and, as they grow, they are less and less. The adult molts once every 1.5-2 years. During the molting, the crab loses a lot of strength, it is under considerable stress.

In the aquatic area of ​​the home you can start aquaterrarium and ornamental fish. The rainbow crab is perfectly calm with danios, quills, swords, and a few other species of fish. Small turtles and shrimp also do not interfere with the “patriot” who goes about his business calmly.

As you know, almost all types of crabs are scavengers and foragers. This means that they will never look for your food, but instead will eat something that you can safely drink.

As the natural ration of these animals mainly includes vegetation, they gladly eat some vegetables (pumpkin slices, cabbage, sliced ​​carrots) and also vegetables: spinach, dandelion leaves, lettuce. You can also give fruits: bananas, pears, apples and even oranges.

The daily menu should include foods of animal origin, including frozen ones. It can be shrimp and mussels, pieces of chicken and beef liver, or traditional fish food – bloodworms, gammarus, crickets.

In principle, food should be varied and contain enough calcium, which contributes to a more relaxed passage of the molting period.


If we talk about reproduction, achieving it at home is almost impossible. In nature, it occurs in seawater, taking into account all the characteristics of the natural biotope. True, the owners of handsome rainbow men have repeatedly observed clear signs of mating behavior.

The life of a bright and slightly amusing indigo crab at home is always a curious sight that can be watched for hours. This superior crustacean is observed to have the intellect that enables it to recognize its owner and even take food from their hands.

Although sometimes it is not entirely clear who is the true owner of the situation: a person or a large domestic crab, calmly and with dignity, accepting their care?

Aqua Terrarium for crabs

Creating the conditions in the fence for the life of these beautiful crabs is not easy, since they spend more time on land than in the water. In the usual aquarium, without soil, crabs cannot exist.

Therefore, they are not contained in aquariums and aquariums. It can be done from an aquarium by filling the tank not completely, but 10-15 centimeters, and several stones should stick out of the water.

Also, in nature, the size of rainbow crabs is quite large: the diameter can reach up to 16 centimeters, so they need large aquariums. For an individual, the area should be 50 by 40 centimeters.

Rainbow crab (Сardisoma armatum).

Rainbow crabs compete with each other. It will be difficult to feed multiple crabs in tight spaces, as they will take food from each other.

It is recommended to use coral crumb and zeolite as soil, but a mixture of granite gravel with turf crumb is also suitable. The soil particles should not be less than 3-5 millimeters. If there is no soil, then the aquaterrarium should receive a good biofiltration system.

Salt water to keep rainbow crabs or not? They are often successfully kept in freshwater, but they should not be acidic, the pH should be 7.2 to 7.5, and the water should be quite hard, not less than GH 10. High mineralization helps crabs adapt. But at first, water is recommended, however, to add salt, it is desirable to use real sea salt. To 1 liter add 2-5 grams of salt. Salt water reduces the effects of nitrites and ammonia, which are harmful to the waist. Over time, the amount of salt is reduced and equips aquaculture plants.

The optimal water temperature for keeping rainbow crabs is 25-26 degrees.

Rainbow crabs are very sensitive to fluctuations in the temperature of the aquaterrarium.

Often on the Internet there are tips on the arrangement in the aquarium of this sandy beach, in which crabs can dig holes, which they do in nature. But in fact, it often turns out that the sandy beach brings a lot of trouble. Also, creating it is not easy. A drainage washing system will be needed; Otherwise, the sand will be filled with excrement instantly, so the sandy beach will only cause damage.

But why do rainbow crabs dig holes? This is necessary if they are far from the reservoir, so that from time to time it is possible to wet the gills and breathe. That is why the pits of the crabs are deep, they reach the groundwater. In artificial conditions of the crab there is no need for this, since the water is always close, and the crabs spend as much time as necessary.

In addition, rainbow crabs dig holes in the sand to create a safe environment with high humidity.

Rainbow crabs – lovers of mink vision in the sand.

In the aquaterrarium, a large number of all kinds of crab shelters are created, both underwater and on land, so that they can hide and are less aggressive towards each other.

A good option for shelters in the aquaterrarium will be a variety of caves, grottos, ceramic tubes, plastic hooks, flower pots and the like.

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Plants in aquaterrarium with rainbow crab.

Plants effectively remove nitrates from the water, but crabs love fresh vegetables. An easy way to quickly plant a large number of plants. Preference should be given to plants floating on the surface, since everything that is planted in the ground, the crabs are quickly removed. As plants, you can use a rodent, elodea, pemphigus, fern, nayas, duckweed, Japanese moss.

Aquaterrarium for the contents of the crab should be filled with a variety of plants.

Rainbow crab feeding

You can save greenery if you constantly feed your pets spinach, lettuce, nettle, dandelion leaves. It is also necessary to give bananas, pears, apples, oranges, pumpkins, carrots, peas. Also, rainbow crabs are fed fish food, while tablets and granules are very suitable.

Also in the diet should be included crickets, blood worms, mealworms, beef and chicken liver, squid meat, fish, mussels, calcium glycerol tablets. A varied diet high in calcium will help the crabs to shed.

How much live food should the rainbow crab’s diet contain? It should not be more than half the mass of the crab. A large quantity of animal feed can severely contaminate the water with nitrogen compounds that are harmful to crabs.

Due to the diversity of the diet with a high content of calcium, the crabs tolerate the molting process without any problem.

Why do rainbow crabs often die while in captivity?

The body of the crabs is encased in a hard shell. The crabs can only grow in small intervals when they drop the old chitinous cover. While the new shell has not yet hardened, there is an increase.

Molting the crab is the most serious challenge. Naturally, this process is controlled at the level of hormones. At the beginning of the molt affects the nature of the power, the temperature of the water, the intensity of light. At this time, the crab should not contain vitamins. Also, there should be no signs of poisoning from waste products that can accumulate in the aquaterrarium water.

Crabs molt only in water. And not everyone in the water provides their animals with all the necessary meltdown conditions.

Most of the time, rainbow crabs die in captivity during the molting process. Newbies turn multicolored, almost toy children, without even thinking about the responsibility for their content. It is very difficult to mimic natural conditions in a home, so rainbow crabs are often not tolerated by more than one molt.

As you can see, keeping rainbow crabs is not easy at all, it is a real job that requires responsibility.

It is interesting that during the molt not only the anterior covering is discharged, but also the anterior and posterior parts of the intestine. It’s hard to imagine how you can get out of your own stomach, but crabs manage to do it.

There is little data on the frequency with which molts occur near rainbow crabs. Only young individuals are known to molt much more often than adult crabs.

Another common cause of death for rainbow crabs is overheating or, conversely, severe hypothermia in the body. The death of rainbow crabs from heat shock can occur not immediately, but after a few days.

With a strong overheating of the crab molt begins, but the body is not prepared for this process. Therefore, you should not place the stones too close to the heat source where the crabs like to sunbathe. If you touch the stone, it should be a little hot. After the hot stone, go down below.

Rainbow crabs in the wild

You can find these crustaceans in West Africa, Southeast Asia, on the Pacific coast. Rainbow crabs belong to the amphibian species, they live in burrows dug into the sands, sometimes their length reaches one meter in size.

The crabs obtain food in the coastal zone, sometimes the individuals are in a forest, but they return quickly so that other inhabitants do not invade the unoccupied house. Unbelievable is the fact that these creatures always find their home. But the water in the life of rainbow crabs is also present, during reproduction and molting.

Characteristics of the species.

These crabs are not called rainbows at all, they really do have amazing color:

  • blue shield armor,
  • the claws are gray or blue,
  • organ tone varies from bright orange to bright red,
  • Bluish white abdomen.

In addition, the color of the males is brighter, more intense than that of the females. The average lifespan of these crustaceans is 10 years. In nature, individuals. grow Up to 20 cm in size, although when they live in captivity, both indicators turn out to be more modest: pets live less and they themselves are smaller.

It differs from other rainbow crab crustaceans in the way they feed: they do not go to the water, but to land in search of food. Distinguishing the sex of these animals is easy, just look at the abdomen shape – in females it is wide, in males – narrow.

Rainbow crab in aquaterrarium

In order for such an unusual pet to live comfortably, it is necessary to prepare a special tank for it and equip it according to the needs of the crustacean. The following requirements apply to a crab dwelling:

If the crustaceans are kept in small rooms, they will be constantly in conflict, for food or land. Battles can be very difficult and lead to the death of one of the opponents.

When selecting material for embankments, it is necessary to take into account the crab’s passion for digging shelters. If you provide your pet with everything he needs, he will diligently go to work: drag the grains of sand into the water and empty them. Of course, the landscape of such activities of the inhabitants will change, the entire coast will be buried.

It is possible to provide the room with a ready-made dwelling, for this it is enough to lay the clay tube under an inclination so that the crab has a chance to get into it. In this case, the pet will have a house and will not cause a disturbance. You should not use too fine sand, the particle size should be at least 3mm, which will facilitate the siphoning process.

You can decorate the tank to your liking: put pebbles and shells on the bottom, only your crab will be “laid out” as it suits you. The most convenient house for a rainbow crab is an aquarium, but you can also use an aquarium for these purposes. In this case, a 10-15 cm tank is filled with water and settles the earth. It is in this that the pet will most often be: eating, sleeping, just relaxing.

Crabs are very agile and agile creatures, which they often demonstrated in practice, escaping from the reservoir, clinging to the filtration system, a thermometer or the rough surface of the walls. To eliminate such problems, close the tank with a heavy, dense lid that the crustacean cannot move.

If the “patriot” still got away, experts recommend spreading damp cloth rags on the floor and fixing the bowls with water. Crabs, although they live on land, cannot stay in dry air for long, they die. Most of the time, owners find their pets in separate sources of moisture, which saves the life of the crabs.

Water quality and composition.

This handsome man of colors can live in fresh waters. To do this, it is necessary to install a filtration device in the tank so that it removes nitrites and nitrates from the water, which are considered harmful elements for animals.

Once a week, 25% of the water must be replaced, which helps reduce the concentration of harmful components in the aquatic environment. If a small tank with water is installed in the tank, which is the pool, then the water is replaced every day. The parameters of the water are as follows:

  • high mineral content
  • Lasted
  • with acidity – 7.2-7.5.

Almost all of the individuals that can be found in the market are wild crabs caught in the wild. To quickly adapt to the pet, it is recommended to add sea salt, which does not contain additional additives: 1 tablespoon to 5 l. Water

About the right temperature conditions.

The most comfortable krabik feels when the water temperature is from 24 ° to 26 ° С, air – from 27 ° to 29 ° С. If the pet overheats, then it will start to move out of turn, which can lead to the death of the pet. After all, as a rule, the animal’s body is not ready for such changes.

Therefore, it is extremely important to maintain the stability of the indicators. And for this purpose, a movable incandescent lamp is installed in the tank, which can be moved to the necessary areas, heating the favorite places of the inhabitant. If the pet is not properly cared for, it can remain without claws and limbs.

Diet and diet.

In its natural environment, the rainbow crab loves to eat vegetation and also does not reject insects and animals that have recently died. With the menu of a pet’s house, you can prepare the following foods:

  • Lettuce leaves,
  • cabbage of different varieties: broccoli, beijing, brussels, cauliflower,
  • cucumbers
  • beet
  • boiled carrots,
  • pumpkin
  • asparagus
  • green peas

It is forbidden to feed crabs with foods high in copper or starches: parsley, beans, potatoes, celery and pasta. Weekly, but not more often, you can feed your pet food containing animal protein: low-fat veal, chicken or beef liver, shrimp (they are given with shells), fish fillet.

Also, the crab’s diet may consist of dry forage feeding fish or turtles, bloodworms, crickets, mealworms. The blue-red crab cannot be called a gourmet, but it has special preferences. For example, you like to feast on the leaves: oak, maple, and raspberries; they are adapted and dried by experienced owners, preparing for the future.

In the pet menu, you can include fresh herbs and flowers – dandelions, clover, calendula, nettle. They are also recommended to stock up. It is important to provide the crustacean with the necessary amount of calcium. You can add crushed egg shells, chalk, and powdered preparations to food. Feed crabs every 2-4 days, the portion should be small.

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