Thai Micro Crab Care Guide And Best Tank Mates

Species Overview

Common Names: Thai Micro Spider crab, False Spider crab, Micro crab, Freshwater Spider Crab, Laos Micro Spider Crab, Pill-box crab

Scientific Name: Limnopilos naiyanetri

Adult Size: 0.4 inches

Life Expectancy: 1 to 1.5 years


Family: Hymenosomatidae

Origin: Thailand

Social: Peaceful

Minimum Tank Size: 5 gallons

Diet: Omnivore/Detritivore

Breeding: Egg-carriers

Care: Medium

pH: 6.5 to 8.0

Hardness: 6 to 15 dKH

Temperature: 70 to 80 F

The Thai Micro Crab is one of the easiest and most fascinating pet crustaceans you can grow in your home aquarium. They require little maintenance and can be kept by starters in the aquarium industry.

These crabs are small and can grow to be as long as 0.4 inch, therefore, they do not require a lot of space. These interesting crustaceans thrive in various water conditions, making them a very useful hook for your aquarium setup.

Here’s everything you need to know about these amazing little guys.


The Micro Crab, also known as the Thai False Spider Crab, is native to Thailand, Tha Chin River where they lie in the roots of hyacinth. It has been introduced to many countries in Asia, including Japan and South Korea.

The crab is a member of the Hymenosomatidae family of false spider crabs. Its scientific name is Limnopilos Naiyanetri. This crab was named after Professor Phaibul Naiyanetr who worked in the biology department at the University of Chulalongkorn in Bangkok.

The micro crab is a new species that was first described in 1991. It was later introduced in the aquarium industry in 2008.  

Therefore, most details about it like breeding might still be under some research. For instance, so little is known about avoiding the high mortality rate of the newly born Thai Crabs, despite the efforts to imitate its natural habitat.

In Thailand, these crabs are kept due to their small size and ease of maintenance.  However, they are rarely found in fish stores and are largely found in the wild and natural habitats.

This is because breeding them in an aquarium remains a challenge since, after hatching, their babies do not thrive in captivity.


The crab resembles a spider with its long body and ten long legs. They grow up to 0.4 inch long but can live for as long as 1.5 years if properly cared for.

When fanned out, their size increases to about 5 centimeters.

The micro crabs’ appearance is not as vibrant as other aquarium pets, but they are fascinating to watch them as they swim in their tank. They are silvery-gray in color with brown tone legs which are slightly transparent.

The legs are longer than the rest of the body and have claws, which the Thai crab uses for capturing food.

Male and female Thai micro crabs look similar but there are some differences between them as well. Males have large heads while females have smaller heads with less developed eyesight compared to males.

Males have longer antennae while females do not have long antennae like males do. Females also have more rounded bodies than males and a pointy carapace.

The micro crab can grow to be about half an inch long, but most of their growth happens during molting when they shed off their exoskeleton. Molting happens by filing the carapace with water, which cracks the exoskeleton and hardens it so it can grow bigger.

During molting time, it appears to be translucent with a soft body and thus becomes more vulnerable because it cannot protect itself from predators while in this state. However, after the molting process, their bodies will harden little.

You can tell if they have molted if, by looking at them from above, you can see that their carapace and exoskeleton have cracks on them.

Tank Size And Water Parameters

The Thai Micro Crab is a hardy and beautiful freshwater fish. It will thrive in any tank setup, but it is particularly well suited to nano tanks of about 5 gallons.

This is an ideal tank size for a group of 6 crabs because filtration will be well maintained in the tank.

Since they are small creatures, they do not need a lot of space. However, the size of the water tank will depend on the number of micro crabs that you want to bring in.

The most important aspect is to avoid overcrowding them especially if you plan on adding other tank mates.

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These small tanks can be kept in the home as long as they have a Dkh level of between 6 and 15.  The secret is to replicate their natural environment as much as possible so that they don’t notice any changes, otherwise, it might stress them out.

The Crab is not picky about water parameters, so there’s no need for you to worry about keeping the water too hard or too soft or letting your tank get too acidic or alkaline. While they are not picky about water parameters, the temperature must be maintained between 70°F and 80°F.

The only thing you should keep in mind is that these fish prefer warmer waters and a neutral pH balance (pH Levels: 6.5 to 8.0). This means that you may need to keep checking these requirements in your tank if you want these little guys to thrive without issues.

You should also note that these micro crabs are very sensitive to nitrates, thus a nitrate level of more than 10ppm will not be favorable to them. To avoid this scenario, you should set up the tank earlier enough and leave it to cycle for some time before introducing the crabs.

Similarly, avoid any toxins such as chemicals from copper traces or any other element. This will ensure that your crabs are comfortable and have a larger lifespan.

Food And Diet

The Micro Crabs are omnivores. They are fed with algae, as it is easy for them to digest it and also provides them with the necessary nutrients and vitamins.

Mosquitoes and other bugs that live on the surface of the water and feed on algae are a favorite treat for the crabs too. The crabs pick up the bugs with their claws and scoop them directly into their mouths

It is important to have thick vegetation in your tank since crabs love to hide there. You can also find them hiding in the rocks or driftwood.

If you have floating plants that are not too tall, it will be easier for them to hide beneath.

Crabs are generally easy to keep algae-free in a well-maintained aquarium because they do not swim much and thus do not stir up sediment in the tank very often. However, if you notice lots of algae growing on their shells then this may mean that there is too much light entering your aquarium causing more algae growth than usual.

If your crabs are eating algae all the time, then they will have a hard time getting enough protein for their bodies. If this happens, then you need to cut back on the number of algae that they are eating and give them more food with higher protein content.

In this case, you might need to occasionally give them lie or frozen bloodworms and daphnia to complement their dietary requirements.


The Micro Crab is a great choice for a small community tank. They are docile and shy, hiding under the plants and only coming out to explore.

They tend to be shy when first introduced to the tank, but once they get used to their new surroundings, they will become more outgoing.

They do not like bright lights or sudden movements so they should be kept in a dimly lit room with subdued lighting or covered with plants. They also tend to be very curious so they may jump into your hands if you try to move them around too much or touch them up by accident.

They are nocturnal and can only be seen at night scavenging for food. If you want to catch a glimpse of them, you will have to use light.

Not to mention, they can be motionless for hours, thus making it more difficult to see them.

The micro crab is often found on coral reefs or in shallow seas near the coastlines but can also be found as far as 6 miles offshore. It usually lives on rocky reefs, where it hides during the day but comes out at night to feed on small fish and other animals that live in the area.

They are not aggressive towards other tank mates, but in large numbers, they can eat all your plants. They will often display aggression only when mating or defending their territory from other males in their breeding area.

In a peaceful community tank, they are great companions for other small fish like corydoras catfish, tetras and other small tropical fish.


The Micro Crab reproduces by laying eggs which are carried by females until they hatch into tiny larvae called zoea.

This Crab is a very difficult animal to breed in captivity.

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A large number of crabs are produced from the eggs laid by the female. The eggs are orange in color and gradually turn yellow and then eventually grey.

The female holds the larva into the pleon until the end of the larva stage. However, most babies don’t survive.

This is because the zoea stage lasts for 9 days only and it seems impossible to raise them past this stage.

No research has established reasons for the high mortality rate, but it is suspected that the eggs may be too small and therefore hard to maintain. It is also suspected that there may be some sort of parasite present in them that attacks the young crab.

Other scientists speculate there might be a nutrient that is not available in the aquarium but is present in the natural environment. The lack of this nutrient is then what is causing the high mortality rate.


There are three main diseases that affect the micro crab: stress, bacterial infections, and fungal infections.

The stress response of micro crabs is triggered when they are exposed to stressful conditions for a long period of time. Stressful situations include poor water quality, overcrowding, changes in salinity and food availability, high oxygen demand and decreased light intensity.

When these factors occur together, they cause an increase in metabolic rate and can lead to reduced immunity. If stress continues for too long, it can result in death.

The survival rate of micro crabs is therefore dependent on their ability to tolerate stress and recover from it quickly.

Fungal Diseases include white spot disease, black spot disease, and red spot disease. They are caused by a fungus that grows on the crustacean’s body and causes serious damage to the crab’s health.

They cause lesions on the body of the shrimp causing them to become discolored or lose their color altogether. The crabs show symptoms such as weak coloring, loss of appetite and behavior changes.

Bacterial infections include DML (diplostomum malum), MCL (mycobacterial keratitis), and CMV (cytomegalovirus). They are caused by bacteria that infect the crab’s body causing ulceration on the surface of its shell.

The infected crustaceans will then die off within a short amount of time unless treated properly with antibiotics or antivirals.


Because of their small bodies, the micro crabs are vulnerable to a lot of predators and harsh environmental conditions. However, when put in optimum water conditions, they can live for 1.5 years.

If you intend to keep them in your water tank, you should be very cautious of the water since they are highly sensitive to any changes in the water.

Tank Mates

The Thai micro crab is a small, delicate creature that needs the right tank mates to thrive. Many small tank mates can be introduced at the same time so that they do not compete for food or space.

For example, if you are adding more shrimps and snails, the micro crabs will eat the shrimp and snail eggs. In addition, since these crabs are sensitive creatures, they should be kept in a well-planted tank with plenty of hiding places.

One of the most important things to consider when choosing a tank mate is whether or not it will eat your Crabs. Here are some of the most peaceful tank mates that can share a tank with the little peaceful creatures.

1. Cherry Shrimp

Cherry shrimp are peaceful little crustaceans that will not bother other fish in your tank so long as there is enough room for them to swim freely around the aquarium. However, they should be kept with other non-aggressive fish, so they do not become overstocked.

The Cherry Shrimp needs similar care conditions as Micro Crab. Due to their ability to eat algae in the tank and their peaceful nature, Cherry shrimp can cohabit well with the micro crabs without any major issues.

2. Pygmy Corydoras

Pygmy corydoras are an ideal tank mate for micro crab. They are small, peaceful and active fish that will not cause any problems to your micro crab.

The pygmy corydoras should be kept together in the same tank because they are a community fish that live together in a group.

Pygmy Corydoras are omnivores. They will eat sinking flakes or frozen foods and should be fed sparingly as they can easily become obese if fed too much or too quickly.

3. Harlequin Rasbora

A Harlequin Rasboras is peaceful and make good community fish that thrive with other peaceful species. They can be kept with other small peaceful non-aggressive crustaceans like the Thai Crab.

Their size and peaceful nature are elements to consider, which make them ideal tank mates.

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Harlequin Rasboras and micro crabs have the same tank requirements. They prefer soft water conditions, but they also do well in slightly harder water as long as they have plenty of oxygen.

They lay eggs in dense vegetation near the surface of the water where they hatch after two days or so.

The Harlequin Rasbora is an omnivore and feeds on both plants and meaty foods. However, it does prefer meaty foods over plant matter. It will accept most types of pellets, flakes and flake food. Freeze-dried blood worms are also a good diet for your Harlequin Rasbora.

4. Cherry Barb

Cherry Barb is fairly peaceful in the aquarium that will lie in harmony with micro crab. They should be kept in groups of at least four to six individuals.

Cherry Barb is a fantastic fish for the aquarium.  It is an omnivore and just like the micro crab, it will eat most small food pellets, flake foods, and frozen foods.  It will also eat crustaceans, worms, snails, and small insects. 

Frequently Asked Questions

Can Micro Crabs Live With Shrimp?

Crabs and shrimp share many commonalities in their biological makeup, behavior and environmental requirements. Micro crabs are a great addition to your shrimp tank!

Not only do they help keep the ammonia levels down, but they also do a lot of cleaning for you. The Micro crab does well in tiny tanks along with shrimp. They do not get big and have no problems fighting with other tank mates, unlike other crabs who can easily upset an established tank.

Do Micro Crabs Breed?

If you have been keeping a micro crab in an aquarium for a while, and you want to breed them, firstly it must be a male and female crabs at the same time. And then, you need to do something that they love, feeding them well.

They do breed but babies might not survive.

Do Micro Crabs Escape?

The crab is quite nervous so be sure not to scare it by touching it. Sometimes crabs will make movements like they’re about to run but it’s just their natural instinct to survive and what they do every time they feel threatened.

Those who have these crabs as pets should ensure that the crabs have plenty of space and shells available for them to escape into when they feel threatened.

Are Micro Crabs Aggressive?

The micro crabs are actually not aggressive at all, they will allow even smaller fish to share the same tank. Micro crabs need to be conditioned over a period of time before they get used to other creatures in the tank, but they display no hostile behaviour if you do choose to introduce them.

Micro crabs can get aggressive with their claws, and it is better to keep them in a large enough tank with wide and long spaces for them to retreat into.

Do Micro Crabs Need A heater?

The micro crabs do not require a heater. They can be kept at room temperature, but they will suffer if the temperature drops below 70 degrees F (21 C).

In warmer locations, a heater is not needed. The crabs are more active when they are warm and will move around more.

They also like to be kept in water that is between 73-78 degrees Fahrenheit. If the water is too cold they will stay in one place and become inactive, but if it’s too hot they won’t stay still either.

How Long Do Micro Crabs Live?

If the micro crabs are fed well and are nurtured in great water conditions without being threatened by other creatures, they can lie to a maximum of 1.5 years.

Will Crabs Eat Shrimp?

Yes, crabs eat shrimp. However, the crab will only eat shrimp when it is small enough to fit into its mouth. If the shrimp is too big for the crab’s mouth, it will be ignored.

Final Thoughts

Overall these crabs make great fish tank companions and loyal pets. When choosing a tank mate for these crabs, it is important to do some research on what kinds of fish and other aquatic animals are safe for them to be with.

If you don’t want your Thai Micro Crab to become lunch, then consider some of the tank mates that we’ve outlined above.

These little beauties are a great invertebrate to have as a beginner because they are resilient to temperature changes, very peaceful and can be housed with most other small-sized tank mates. If you do choose to get them, adhere to this care guide for tips to set up their new home and what to feed them.


Passionate fishkeeper. Nature lover. Creative thinker. Music junkie. Adventurer.

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