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Thai Micro Crab Care: Here’s What You Need To Know

Thai micro crabs, also called false spider crabs, are only found in one river in Thailand. Because they are only found in one place and are so small, they make an exotic and unique addition to your varied aquarium or shrimp habitat.

They are super adaptable and one of the only fully aquatic crab species in the world. They get the name of false spider crab because of their very long legs compared to their tiny shell (hardshell). These tiny creatures are a bit difficult to care for as they are completely helpless and need high-quality water.

If you’re interested in adding some variety to your tank, you’ve come to the right place to find out everything you need to know about Thai micro crabs, which have quickly gained popularity among aquarium hobbyists. Do you want to know more about this wonderful possible member of your aquarium? Keep reading!


The scientific name of the Thai micro crab is Limnopilos naiyanetri. In addition to false spider crabs, these tiny aquatic crabs are also known as pill-box crabs. Because these crabs are relatively discovery and are only found in one river in Thailand, it can be challenging to find these peaceful creatures online or in pet stores.


The Thai micro crab originates from the Tha Chin River, which is in Thailand’s Nakhon Pathom province, and they live in the roots of the water hyacinth plant. The genus Limnopilos is part of the Hymenosomatidae family and was first described to the scientific world in 1991, making it new to the aquarium scene.

It was briefly equated with Hymenicoides but after scientists discovered some distinctive features, it was once again classified with the genus Limnopilos.

Life span

Because the Thai micro crab has only been studied for the last 30 years or so, there is not much information about its life in the river. But in a controlled aquarium environment, a Thai micro crab can be expected to live for a year to a year and a half. If you take good care of them, they could last even longer.



Thai micro crabs are translucent gray and silver or brown, and their legs are like beige. They sometimes have a pattern on their shell. These micro crabs are equipped with 10 legs, which they usually stick under themselves.

As we mentioned before, those very long legs (relatively speaking, of course) are covered in shaggy bristles, just like the rest of their bodies, a feature that aids in food gathering.

Average size

As alluded to earlier, Thai micro crabs resemble spiders in that their legs are very long relative to their body size. But even with the long legs, the micro describes them well, they are tiny. It measures at most more than 0.4 inches, with a transparent silver-grey pattern.

The Thai micro crab, a scavenger, is covered in tiny hairs that help it grab hold of food particles. In its adult state, the shell of the Thai micro crab is just under half a centimeter wide. Those “long” legs we’ve been talking about are 1-inch carapace length (carapace width) is only about 0.4 inches long.

If you think that sounds small, you’re right. This species is the smallest known freshwater crab.

Expert Tip: Because they are so small, they are often preyed upon by larger, more aggressive animals and fish. They rarely feed on other creatures except for tiny baby shrimp and snails. Even the plants in your aquarium are safe with them, although the Thai micro crab has no defense in its tank.

Thai micro crab care

Thai micro crab care
Thai micro crab care

Thai micro crabs are friendly and social creatures, they prefer to be in groups with other Thai micro crabs. They differ from other crab species in that they are more territorial and sometimes the male’s fight. Thai micro crabs get along with each other and hide in common places.

A good way to care for your Thai micro crabs is to make sure they have a community of 5 or 6. These crabs enjoy the currents of their natural river environment, so if you can add a small powerhead to your aquarium to create some water flow in the tank, you will have some contained crabs that can stay active.


Thai Micro Crabs Shedding
Thai Micro Crabs Shedding

Like other crab species, Thai micro crabs shed their skin. However, due to their compact size and very slow growth, they do not shed as often. The process, however, is similar to the molting process of other crabs.

The molting activity begins with the Thai micro crab filling its shell with water, which helps separate the crab’s exoskeleton. The pressure of the water also opens the exoskeleton. As a new shell forms, the Thai micro crab crawls out from under the old one.

The Thai Micro Crab will look translucent after molting as it is still heavy and soft water. Hardening occurs over three days or so. Don’t be surprised if you find the old skeleton on the floor of your aquarium.

The already defenseless crab is even more vulnerable during molting time. It is a good idea to delay cleaning until the crab is finished molting to prevent any additional injury or stress to this little creature.

Tank size

The minimum tank size is 2.4 gallons. However, depending on the number of micro crabs you have in your aquarium, you may want a 5 gallons tank, which would fit a colony of half a dozen quite well.

Water parameters

You must recycle the aquarium water before adding your Thai micro crabs and make sure the tank is mature. You can mature a new aquarium by adding the water from an already mature tank to the new water, or several other accepted methods.

Failure to fully and carefully acclimatize Thai micro crabs to their new environment can be fatal. You have to check the water levels often and also change the water regularly, as well as watch for good bubbling on the surface of the tank.

Expert Tip: The recommended water temperature range for Thai Micro Crabs is 22-28 Celsius degrees (or 72-82 Fahrenheit degrees) and the best pH level is 6.5-8.0 and the water hardness should be between 6-15 kg.

What to put in their tank?

What to put in their tank?
What to put in their tank?

After making sure you have high-quality water conditions and a quality filter, you need to make sure you have plenty of plants (especially floating ones), caves, wood, and other decorations to make your Thai micro crabs feel cozy and have fun, the best hiding places.

Since they like to hide, you may want to choose colors that contrast with the color of your Thai micro crab, to ensure that you see them. In addition to floating vegetation, good plant choices for Thai micro crabs include ferns, anubias, and mosses are the long roots of these plants that simulate the hyacinth in its native environment.

Common Possible Disease

As we have seen before, not much is known about the common diseases of this species because it was discovered relatively recently. Despite this, it is known that they are susceptible to bacterial and fungal diseases. Another disease that not only affects the Thai micro crabs but the vast majority of the members of an aquarium is stress.

This disease can be fatal. To prevent these diseases from affecting our micro crabs, we must maintain the quality of the water in perfect conditions, and most importantly, avoid sudden changes in the parameters. If you manage to achieve the desired stability in the quality of the water, taking care of these crabs will be a breeze.

Another important thing that we must take into account to avoid stress in our micro crabs is not to overpopulate the aquarium, even with species compatible with crabs. This is because although they are peaceful they will be taken as potential enemies by our Thai crabs.

Food & Diet

Thai Micro Crabs Food and Diet
Thai Micro Crabs Food and Diet

As we have seen in the appearance section. Thai micro crabs are covered in bristly hairs so that they can filter water through them as they forage for food they will eat plant root particles and algae. They are omnivores and detritivores (organisms that feed on the dead matter), so they are not too picky about what they eat.

Shrimp feed and sinking pellets are good supplements for Thai micro crabs, and in addition to the particles they get from plant roots, they will forage on mosses and algae.
Thai micro crabs eat the particles that get stuck in their bristles as they clean themselves.

It is good to remember that the Thai micro crab is not aggressive and therefore does not hunt its food, but rather eats what it finds. If you have a new aquarium that doesn’t have a lot of biofilm and decay, your Thai micro crab would appreciate some dry plant-based food, blanched vegetables, and algae wafers.

If you are managing a mature aquarium, you may not need to supplement the diet of your group of Thai micro crabs, as there is likely to be enough food for them to scavenge. However, if you have dwarf shrimp, the crabs will lose the race for food.

Behavior & Temperament

Behavior & Temperament
Behavior & Temperament

When you introduce your new Thai micro crabs to your aquarium, you will find that they are shy and introverted. They like to have places to hide, even after they become more comfortable in their surroundings. They will be happy if you put some plants and caves in the tank so they can hide whenever they want.

Expert Tip: They are also nocturnal creatures, so you won’t see much of them during the day. Consider investing in a bright light bulb so you can see them at night.

As they settle into their new home, you can watch them chilling on the driftwood you’ve prepared for them or hanging out on the plants in the tank.


The Thai micro crab needs a peaceful environment because it is so small and has no way of defending itself from aggressive predators. Thai micro crabs thrive when living together in groups of 5 or 6, it makes them feel more secure.

They can also be paired with small schools of fish, soft fish such as Pygmy Corydoras, Otocinclus catfish or Zebra Danio, and small shrimp and snails. Avoid pairing Thai micro crabs in a tank with other types of crabs, which are sure to have for dinner.

Other poor choices for your Thai micro crab community are crayfish and other aggressive fish, such as cichlids.

Good tankmates

  • Small school fish Ramshorn snails
  • The Otocinclus catfish
  • Nerita snails zebra danio
  • Neocaridine Shrimp

Poor tank mates

  • Other crabs
  • Angelfish
  • The big catfish Tetras Goldfish Cichlids River Crabs

Thai Micro Crab Breeding

Thai Micro Crabs Breeding
Thai Micro Crabs Breeding

Until now, aquarium enthusiasts have not been able to breed with Thai micro crabs within the confines of a tank. Conception and gestation have not been problematic, however, the young of the Thai micro crab do not survive after hatching.

Something unidentified in the natural environment does not reproduce in captivity. What does Tha Chin River have that its aquarium doesn’t? Maybe it’s the water temperature. pH. hardness, current, or something else.

Some eager breeders speculate that there might be a particular nutrient in the natural environment, be it a type of algae or something in the hyacinth, that is missing in the aquarium. Others wonder if, like other crab species, the Thai micro crab lays its eggs on land in the natural habitat.

However, our evidence shows that like other aquatic crabs, the Thai micro crab holds up to 200 eggs within its abdomen. Therefore, the terrestrial option does not seem feasible, particularly as we know that the Thai micro crab is entirely aquatic. It has also been shown that baby Thai micro crabs need a beacon of light to connect.

So if you are trying to breed (not recommended until more is known about improving survival rate), use lighting above the tank to orient the babies. The fact is that at this time, although there have been cases of Thai micro crab eggs hatching and forming from larvae into baby crabs, the micro crabs have not survived much beyond a week.

The process of raising Thai micro crabs

Fertilization is internal. The sperm will expand from the male gonopod to the female. After fertilization, the female stores a group of up to 200 eggs in her abdomen (pleon), Thai micro crabs have an average of 70 hatched larvae.

It is interesting to note that after the eggs hatch, the female Thai micro crab does not release the larvae into the tank environment. Rather, she continues to hold them in her pleon until the end of the larval stage, at which point she releases the baby Thai micro crabs into the water. This gestation process lasts for several weeks.

When the larvae are released from the mother’s pleura prematurely, the baby Thai micro crabs are eaten by the male crabs. Because baby crabs are released later in development, they do not go through the seawater or brackish water phase.

The appearance of Thai micro crab eggs

Because the female Thai micro crab rarely opens her suit flap or her abdominal apron, it is challenging to get a good look at the crab’s eggs. The pleon is translucent so you can see the eggs through film. The eggs start with an orange tint and end with a gray color, with a yellow period between them.

Compared to the size of the Thai micro crab, its eggs are quite large. The eggs measure .5-7 mm while the mother crab measures 1 cm. That means that with 70 eggs at the smaller end of the range, the egg cluster is just under an inch larger than the king crab.
Distinctions between male and female Thai micro crabs

As you can imagine, the small size of the Thai micro crab makes it difficult to distinguish between males and females. In addition, they are incredibly fragile and cannot withstand the handling that a physical exam entails.

But if you have a magnifying glass, and you can put the Thai micro crab in a position where you can see its underside, you will notice a difference in the bottom flap. Males have a narrow, tapered lower flap, while females have a broader lower flap.

Other than that, it’s almost impossible to tell the difference, unless, of course, you’re looking at a female carrying a cluster of eggs or larvae. You might wonder why you keep a little crab that likes to hide in your aquarium.

What fun is that? But Thai micro crabs aren’t completely invisible and when they do come out. they look great, hanging on a floating plant or searching the bottom of the tank for food. Additionally, the Thai Micro Crab is a gentle and personable member of your aquarium community.

It contributes to a healthy biome. it’s not a threat, and let’s face it, it’s great to have a little aquatic spider dancing in your aquarium.

Expert Tip: Keep in mind that if you want to enjoy your micro crabs, use a smaller tank. They are so small that they will get lost in a large aquarium.

Can Thai micro crabs live with bettas?

Limnopilos naiyanetr is the scientific name for Thai Micro Crabs, popularly known as “false spider crabs.” These are small, totally aquatic crabs that have only been discovered in one river in Thailand so far.

They are omnivores and detritivores (organisms that devour dead materials), so they don’t have a lot of food preferences. Thai micro crabs will eat shrimp food and sinking pellets and particles they acquire from plant roots, and they will graze on moss and algae.

The betta (Betta splendens), is commonly termed as the Siamese fighting fish. This is a freshwater fish native to The Tropical, specifically in Cambodia, Thailand, and other places. Betta splendens species is typically recognized as a betta due to its worldwide popularity as a pet.

This is a cause of their varied and vivid colors, variable morphology, and minimal maintenance requirements, they are among the most widely accessible aquarium fish in the world. No, they aren’t even close to being compatible. Fiddler crabs prefer a brackish environment and will try to catch any fish they come across.

Are Thai micro crabs shrimp safe?

This is a question that many people may be asking, and the answer is not always very clear. While most crabs that are consumed in the United States are safe, this is not always the case with crabs from other countries. In general, most crabs that are consumed in the United States are safe.

However, there are a few exceptions. For example, some crabs from Thai and Hawaii may contain toxins that can make people sick. In addition, some crabs from other countries may contain bacteria or parasites that can make most people sick.

If you really are looking for a safe and delicious seafood option, shrimp may be a better choice. Shrimp is a good source of protein and omega-3 fatty acids, and they are low in mercury. In addition, shrimp are easy to prepare, and they taste great with a variety of sauces and seasonings.

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