Fish and other aquatic creatures

Rainbow crab


This representative of crustaceans is perhaps the most popular inhabitant of domestic aquaterrariums. But this statement is true for foreign animal lovers, and in our country it can be found not so often. And it is completely in vain, as it can decorate any living corner in a house or apartment. The name of this bright exotic beauty is the rainbow crab.


According to the structure of its body, the rainbow crab is a typical representative of a group of decapod crustaceans. But the color of his unusual, bright and attractive. The shell is painted in dark blue (for some individuals it is purple), the legs are red or orange, the large claws are usually gray, but there are also bluish. The belly of the crab is usually pale white, sometimes blue-streaked. The size of an individual can reach 20 cm in diameter.

Such a palette of colors and shades contributed to the presence of many names. According to the scientific classification, this crab

  • in Latin 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 (tri-color crab),
  • due to the fact that this crustacean leads mainly to the land way of life, it is also called the Land crab (land crab).

Place in the animal world

Indeed, Cardisoma armatum spends most of its life on land. The area of ​​distribution 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 itself digs holes, which serve as a refuge and a place for rest. Near this refuge, he spends most of his life searching for food.

If it is not nearby, the multi-colored arthropod is cheerfully sent in search of food in the nearest thicket. You can be sure: there he will definitely find something to feed.

But sometimes incidents occur when, returning to his sandy house, the “traveler” finds him occupied by another member of the species. In fact, why would an invader dig a hole for himself if he finds one already prepared?

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

But in the brackish ocean water this animal rarely enters. This happens only during the mating season and during the molt. However, in fresh water, he feels great, which allowed some scientists to consider the rainbow crab not only ground, but also freshwater.

Sex characteristics are mild, but experts determine the sex by the appearance of the abdomen - the back of the abdomen. If it is narrow in males, it is much wider in females and resembles an obtuse triangle in shape. In addition, females are often larger than males.

Home conditions

These conditions can not be called simple, as for the life of Cardisoma armatum in captivity, you need to equip the aquaterrarium. What does this mean?

Home Improvement. For the optimum content of the rainbow crab in a normal aquarium, 2 zones are arranged: water and coastal (land). This simulates natural habitat conditions.

The glass container may be shallow, since the water portion is filled to a level of 12–15 cm. Zoning may be equal (zones are approximately equal in area) or with the advantage of water cover.

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

That is why the optimum interior is a sandy land zone, fenced off from a water stone ridge (to prevent erosion of the coastline).

Sand should be a large fraction, can also be used as a small pebble, shell rock or small gravel. If you pour in ordinary 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 itself, is instilled into the ground at an angle of 45 °. It is funny to watch how an animal climbs there, captures the soil that has accumulated below and, pressing it against the body with its claw, brings it to the surface.

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

In addition, there should be a constant temperature in the aquaterrarium itself ranging from + 25 ° C to + 28 ° C. The level of pH balance must be maintained neutral, and the hardness may be increased, but not more than 20 °.

Constantly you need to monitor the purity of water, which is achieved using a filter. At the indicated low water level, an internal or external filter of medium or low power will be suitable, 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.

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

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

Behavior and Compatibility

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

As a rule, battles do not begin immediately, the escalation of tension occurs gradually. At first there may be attempts at capturing the mink, then the rivals will try to take food away from each other and only then the fight can begin. However, the matter does not reach serious battles.

To avoid conflict situations, some owners of several rainbow creatures arrange a separate dry zone for each occupant of the aquaterrarium. In this case, please note that for one animal at least 0.4 m² of its own territory is required.

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

In the water area home aquaterrarium you can start and ornamental fish. The rainbow crab perfectly calmly gets on with danios, barbs, swordtails and some other species of fish. Small turtles and shrimps also do not interfere with the "patriot" calmly go about their business.

As you know, almost all types of crabs are scavengers and gatherers. This means that they will never hunt for their food, but rather eat something that you can safely take.

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

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

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


If we talk about reproduction, then to achieve it at home is almost impossible. In nature, it occurs in sea water, taking into account all the features of the natural biotope. True, clear signs of mating behavior have been repeatedly observed by the owners of rainbow handsome men.

The life of a bright and slightly funny indigo crab at home is always a curious sight that can be watched for hours. It is noted that this higher crustacean has the intellect that allows it to recognize its owner and even take food from his hands.

Although it is sometimes not entirely clear who is the real master of the situation - a person or a large domestic crab, with calmness and dignity, accepting his care?

Aquaterrarium for crabs

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

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

In addition, in nature, the size of rainbow crabs is quite large - the diameter can reach up to 16 centimeters, so they need spacious aquaterrariums. For one 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 several crabs in tight spaces, as they will take food from each other.

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

Salt water to keep rainbow crabs or not? Often they are kept successfully in fresh water, but it should not be acidic, the pH should be 7.2-7.5, and the water should be quite hard - no less than GH 10. High mineralization helps the crabs to adapt. But at first, water is recommended, nevertheless, to add salt, it is desirable to use real sea salt. At 1 liter add 2-5 grams of salt. Salt water reduces the effects of nitrites and ammonia, which are harmful to crabs. Over time, the amount of salt is reduced and equip aquaterrarium plants.
The optimum water temperature when keeping rainbow crabs is 25-26 degrees.

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

Often on the Internet there are tips on the arrangement in the aquaterrarium of this sandy beach, in which crabs can dig holes, what they do in nature. But in fact, it often turns out that the sandy beach brings a lot of problems. In addition, to create it is not easy. A drainage washing system will be needed, otherwise the sand will instantly be filled with excrement, therefore the sandy beach will only bring harm.

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

In addition, rainbow crabs dig holes in the sand to create a shelter with a wet microclimate.

Rainbow crabs - lovers of digging mink in the sand.

In the aquaterrarium create a lot of all sorts of shelters for crabs, both underwater and land, so that they can hide, and were less aggressive to each other.

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

Plants in aquaterrarium with rainbow crab

Plants effectively remove nitrates from water, but crabs love fresh greens. The easiest way to immediately plant a large number of plants. Preference should be given to plants floating on the surface, since everything that is planted in the ground, crabs quickly pull out. As plants, you can use a rodentary, elodeyu, pemphigus, fern, nayas, duckweed, Japanese moss.

Aquaterrarium for the content of the crab must be filled with a variety of plants.

Feeding rainbow crabs

You can save the vegetation if you constantly feed your pets with spinach, lettuce, scalded nettle, dandelion leaves. You also need to give bananas, pears, apples, oranges, pumpkins, carrots, green peas. In addition, rainbow crabs are fed with fish feed, while tablets and granules are well suited.

Also in the diet should be crickets, bloodworms, meal worms, beef and chicken liver, squid meat, fish, mussels, tablets of glycerol calcium. A varied diet with a high calcium content will help crabs to shed.

What amount of live food should be in the diet of rainbow crabs? It should not be more than half the mass of the crab. A large amount of animal food can severely pollute water with nitrogen compounds that are harmful to crabs.

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

Why do rainbow crabs often die when kept in captivity?

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

Crab moult is the most serious challenge. In nature, this process is regulated at the hormonal level. At the beginning of the molt affects the nature of power, water temperature, light intensity. During this period, the crab should not be deficient in vitamins. Moreover, there should be no signs of poisoning by waste products that can accumulate in the water of aquaterrarium.

Crabs molt only in water. And not all aquarists provide their pets with all the necessary conditions for molting.

Most often, rainbow crabs die in captivity during the process of molting. Newbies get multi-colored, almost toy kids, without even thinking about the responsibility of their content. It is very difficult to imitate natural conditions in a house, which is why more than one molt often rainbow crabs do not tolerate.

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

It is interesting that during the molt not only the old cover is dumped, but also the back and front parts of the intestine. It is difficult to imagine how you can get out of your own stomach, but crabs manage to do it.

There are few data on how often the moltings take place near rainbow crabs. It is only known that young individuals molt much more often than adult crabs.

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

With a strong overheating of the crab molt begins, but the body is completely unprepared for this process. Therefore, you should not place the stones too close to the heat source on which crabs like to bask. If you touch the stone, it should be a little warm. Ate the stone hot, it is lowered below.

Rainbow crabs in nature

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

Crabs get food in the coastal zone, occasionally individuals find themselves in a forest, but they quickly come back so that other inhabitants do not encroach on the vacated dwelling. Amazing is the fact that these creatures always find their house. But water in the life of rainbow crabs is also present - during breeding and molting.

Features of the species

These crabs are not for nothing called rainbow, they really have an amazing color:

  • armor shield blue,
  • the claws are gray or blue,
  • the tone of the limbs varies from orange to bright red,
  • abdomen bluish-white.

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

It differs from other crustaceans of rainbow crabs in the way of feeding - they go not to the water, but to the land for food. To distinguish the sex of these animals is easy, just look at the form abdomen - in females it is wide, in males - narrowed.

Rainbow crab in aquaterrarium

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

  • the terrarium should be spacious - the size of the tank for one individual should be at least 40 to 50 cm,
  • the dwelling is divided into two zones - water and land,
  • для воды можно использовать обычный контейнер из пластика, предназначенный для пищевых продуктов,
  • глубина воды в емкости – не более 15 см,
  • дно резервуара следует засыпать грунтовым материалом – речным песком, мелким гравием, кокосовой стружкой.

Крабик-индиго не очень рад соседям, поэтому, если предполагается содержание нескольких особей на одной территории, следует каждого из них обеспечить необходимой площадью. If crustaceans are kept in cramped quarters, they will constantly conflict — over food or land. Battles can be very tough 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 you need, it will be diligently engaged in work - drag grains of sand to the water and empty them. Of course, the landscape of such activities of the inhabitants will change, the whole coast will be buried.

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

You can decorate the tank to your liking - put pebbles and shells on the bottom, only their crab will “lay out” as it suits him. The most convenient house for a rainbow crab is an aquaterrarium, but you can also use an aquarium for these purposes. In this case, a tank of 10-15 cm is filled with water and settles the land. It is on it that the pet will be more often - eat, sleep, just relax.

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

If the “patriot” still escaped, experts recommend spreading rags of damp cloth on the floor and arrange bowls with water. Crabs, though they live on land, cannot stay in dry air for a long time, they die. Most often, the owners find their pets at the separated sources of moisture, which saves the life of crabs.

Water quality and composition

This colorful handsome 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 water must be replaced, which helps to 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 water is replaced in it every day. Water parameters are as follows:

  • high mineral content
  • tough
  • with acidity - 7.2-7.5.

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

About suitable 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 he will begin to moult out of turn, which can cause 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 indicators. And for this purpose, a mobile 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 provided with proper care, then it can remain without claws and limbs.

Diet and feeding regimen

In its natural environment, the rainbow crab loves to eat vegetation, and also does not refuse insects and animals that have died recently. With a pet's home menu, you can make up the following foods:

  • greens and lettuce leaves,
  • cabbage of different varieties: broccoli, Beijing, Brussels, cauliflower,
  • cucumbers,
  • beets,
  • boiled carrots,
  • squash,
  • asparagus
  • green peas.

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

Also, the diet of the crab may consist of dry fodder that feeds fish or turtles, bloodworms, crickets, mealworms. Blue-red crab can not be called a gourmet, but he has special preferences. For example, he likes to feast on the leaves - oak, maple, as well as raspberries, experienced owners adapt and dry them, 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 eggshells, chalk, and powdered preparation to food. Feed crabs every 2-4 days, the portion should be small.