Thai Micro Crab Care Guide

Species Snapshot

  • Species Name: Limnopilos naiyanetri
  • Common Names: Thai micro crab, false spider crab, freshwater spider crab, pill-box crab
  • Size: 1cm width, 2.5cm leg span
  • Lifespan: 1 to 1 ½ years
  • Native Distribution: Thailand

Whether you’re looking for a compatible species to add to your shrimp tank or a unique addition to your community tank cleanup crew, Thai micro crabs are a great choice. These tiny crabs are friendly and fairly easy to care for, as long as you provide the proper diet and tank parameters. If you’re looking for an invertebrate that’s easy to breed, however, you may want to stick with shrimp.

Anatomy and Appearance

Known by many names, Limnopilos naiyanetri is most commonly referred to as the Thai micro crab. These little crustaceans only grow to about 1cm in width with leg spans reaching up to 2.5cm. Their bodies are semi-translucent and range in color from light brown to grey.

Thai micro crabs have flat, circular carapaces but what sets them apart from similar species is the bristle-like hairs known as setae lining the carapace. These help collect detritus from the crab’s environment that could serve as food or camouflage.

These crabs are often confused with spider crabs because they have ten long legs. For the most part, however, Thai micro crabs keep their legs tucked under their bodies. While there isn’t much size difference between male and female micro crabs, the females have more rounded bodies. The carapace of a male Thai micro crab is likely to be narrower and somewhat pointy.

Ideal Aquarium Setup

Thai micro crabs are tiny freshwater crabs that do well in nano tanks and other small freshwater habitats. Because they’re so small, they’re quite sensitive to changes in tank conditions. It’s important to maintain high water quality through a good filtration system and regular water changes.

Tank Size

Because they measure just 1cm in width, Thai micro crabs don’t need a significant amount of space. That being said, it’s always better to provide aquarium inhabitants with more space than they need. Thai micro crabs should be kept in an aquarium no smaller than 5 gallons for a group of 5 or 6 crabs. If you plan on keeping your crabs with fish, of course, the tank will need to be much bigger.

Water Parameters

While Thai micro crabs are adaptable to various water parameters, it's best to mimic their natural habitat as much as possible. These crabs are native to one specific river in Thailand where the environment is tropical and the water fairly neutral in pH.

The ideal tank parameters for Thai micro crabs are:

  • Temperature: 72 to 82
  • pH Level: 6.5 to 8.0
  • Water Hardness: 6 to 15 dKH

It’s best to add micro crabs to an already established tank so as to avoid sudden changes in water quality or chemistry. These crabs are particularly sensitive to ammonia and nitrate as well as certain chemicals and heavy metals like copper. Perform frequent water changes to keep the water quality in your crab tank as high as possible.

Tank Décor

Aim to create a natural look with the décor in your Thai micro crab tank. Keep in mind that these crabs come from a heavily planted natural habitat, so they’ll do best in a planted tank that provides plenty of opportunity for foraging.

Include a variety of rooted and floating plants in your micro crab tank. Rooted plants will provide your crabs with shelter and all of the plants will collect biofilm that your crabs can eat. Solid filtration is essential to keep your crabs and your live plants healthy but avoid anything with suction that is too strung as well as strong currents in the water.

Diet and Feeding

In the wild, Thai micro crabs are omnivores – they’ll eat just about anything. In the home aquarium, these crabs are scavengers and will consume everything from biofilm to uneaten fish food. Thai micro crabs use the filaments on their carapace and legs to collect food, though you may also see them feeding directly from plants and algae.

It’s wise to feed your crabs once a day to ensure they get the nutrients they need. Sinking algae wafers, shrimp pellets, or powdered foods are ideal. You may also want to provide protein-rich foods from time to time like live or frozen bloodworms.

Temperament and Tank Mates

Thai micro crabs are incredibly docile, so they’re unlikely to cause trouble with shrimp or other tank mates. They’re very shy by nature and are likely to spend much of the day hiding. These crabs do best when kept in groups of at least 5 or 6 of the same species.

If you’re keeping these crabs with other aquatic species, stick to small, peaceful species like guppies and small barbs or tetras. Avoid keeping Thai micro crabs with large or even medium-sized fish that might see them as a snack.

Some aquarium hobbyists have had success keeping their micro crabs with bettas but be careful about this pairing because betta fish are carnivorous.

Breeding Thai Micro Crabs

If you’re hoping to breed your Thai micro crabs, you should temper your expectations. This species is notoriously difficult to breed and there are no documented instances of reproduction in captivity. What makes breeding Thai micro crabs tricky is that they release free-moving larvae, and it is unknown whether they develop in freshwater or saltwater.

There is some anecdotal evidence of Thai micro crabs breeding in aquarium settings simply because the crabs do it of their own accord. The trouble is that the baby crabs die before they reach maturity. No sound method has been discovered to significantly improve mortality rates.

Other Interesting Facts

  • Thai micro crabs are a very low-maintenance species – they don’t require brackish conditions like some crabs and they’re adaptable to various temperatures. They aren’t picky about water parameters but should be protected against sudden changes in water quality.
  • Unlike many crabs, Thai micro crabs are fully aquatic – they do not need access to land because they spend the entirety of their lives underwater.
  • There’s not a lot known about the diseases to which Thai micro crabs are prone, but they can be affected by the same fungal and bacterial infections as other crabs. Stress is a common trigger for disease and is often brought on by poor water quality, so keep your crab tank clean.
Like most invertebrates, Thai micro crabs molt from time to time. If you spot what looks like a dead crab in your tank, it could be just a molted shell.
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