A relatively recent addition to the aquarium hobby, Thai micro crabs are quickly gaining popularity. They are appreciated among shrimp keepers for their very peaceful nature and similar requirements to shrimp, which make them a great option if you're looking for tankmates for your (dwarf) shrimp colony.

Keep reading for everything you need to know about Thai micro crabs and keeping them in your home aquarium!

Scientific nameLimnopilos naiyanetri
Common namesThai micro crab, Thai micro spider crab, false spider crab, pill box crab
Difficulty levelModerate
OriginThailand

Thai micro crab natural habitat & appearance

Natural habitat

As mentioned, the Thai micro crab hasn't been available in the aquarium hobby for very long (it was first introduced to the market in 2008, specifically). That's not surprising, given the fact that it was only discovered in 1991! It was the first member of its genus, Limnopilos, to be described scientifically.

At first, it was assumed this was a mistake and that the Thai micro crab actually belonged to the existing genus Hymenicoides. In 2007, though, the original description was validated when it was discovered Limnopilos and Hymenicoides really aren't the same. Today, there are three known species of Limnopilos, with the Thai micro crab (Limnopilos naiyanetri) being the most well-known.

As its name suggests, this crab is naturally found in Thailand. Specifically, as far as we can tell, it has only been spotted in a single river called the Tha Chin. Here, it inhabited the roots of floating water hyacinth plants, which interestingly aren't even a native species in this river.

The IUCN Red List has not classified this species, but unfortunately, it is known that its natural habitat is threatened by pollution.

Appearance

They're not called "micro" crabs or pill box crabs for nothing. These guys are TINY! Their carapace is usually less than 0.5" in diameter, and even with the legs included, they don't tend to surpass 1".

Thai micro crabs are greyish to beige in color, with spidery legs and small claws. They're notably hairy, with their "fur" probably allowing them to catch edible particles.

Thai micro crab

Setting up a Thai micro spider crab aquarium

Requirements

As mentioned in the introduction, Thai micro spider crab care and requirements are relatively similar to those of dwarf shrimp. A large aquarium is not needed for these crabs. A small colony (up to 10) can be sustained in an aquarium of at least 5 gallons (19L), as long as it's fully cycled and heated. A sponge filter should be adequate.

This being said, because they don't respond well to low water quality, keeping these crabs in a slightly larger tank (10+ gallons) might be easier. A larger volume of water will be easier to keep stable.

Like dwarf shrimp, Thai micro spider crabs can be quite shy. They need plenty of hiding places to feel safe. Adding decorations and plants is a good idea. As mentioned, this species was discovered in plant roots, so try some floating plants with long roots to match their natural habitat.

Did you know? Thai micro crabs are nocturnal, so no worries if you don't spot yours much during the day. You could install a night light on your aquarium to see them out and about after dark.

Water quality

Thai micro crabs can be rather fragile, which means the aquarium should have had time to properly mature before they are added. A close eye should be kept on the water quality at all times.

Do regular water tests using a liquid test kit and perform weekly water changes using temperature-matched water.

pH: 6.5-7
Temperature: 71.5-82.5 °F (22-28 °C)
Hardness: 70-150 ppm

Limnopilos naiyanetri crab
Thai micro crab

Tankmates

Thai micro spider crabs are extremely docile and should always be surrounded by similarly calm tankmates. (Dwarf) shrimp like cherry shrimp or Crystal Reds would be the ideal choice, as these require very similar conditions in the aquarium

You can also keep them with small peaceful fish species such as pygmy Corydoras and Microrasbora. Never combine your Thai micro spider crabs with larger fish that might have a taste for crab legs, as they are completely defenseless. Those tiny claws are for eating, not fighting!

Like most inverts, the Thai micro crab appreciates the company of its own kind. They should be kept in small groups of at least three to help them feel safe.

Thai micro crab diet

Thai micro crabs have small hairs on their claws. In the wild, these are used to catch any small food particles the crabs can find while foraging among aquatic plants. They're omnivores and definitely not picky when it comes to food: detritus, small bugs, and plant bits are likely all welcomed.

In the aquarium, your crabs will spend much of their time foraging for micro-organisms in plants and algae. Be sure to supplement their diet with a high-quality food to prevent them from going hungry. Shrimp foods contain all the nutrients your crabs need and should work well.

thai micro crab

Breeding Thai micro spider crab

When these crabs hit the market, it quickly became clear that their reproduction is similar to that of lower-order shrimp: they don't produce fully developed mini-copies of themselves, but larvae that must metamorphose multiple times first.

At first, some aquarists thought that Thai micro crabs were like Amano shrimp in that their larvae hatched in freshwater, but then needed brackish water to develop before moving back to fresh. It now appears, though, that they're more like ghost shrimp—spending their entire life cycles in freshwater. This has apparently been confirmed by the scientist who discovered them.

Whatever the case, Thai micro spider crab breeding is definitely not an easy task. It seems no aquarist has managed to do (and document) it yet, although some appear to have come quite close. There have been reports of baby crabs popping up in heavily planted tanks, but no specifics on the process.

Female crabs do become pregnant (gravid) and even get as far as releasing their larvae, but in the end, these just die before they can mature. An interesting project, so be sure to give it a shot! You may make aquarist history.

Frequently asked questions

Can Thai micro crabs live with African dwarf frogs?

We're not huge fans of the idea. Although Thai micro crabs may be a little too big to fit into an African dwarf frog mouth, these frogs are still bug eaters, so it's not an ideal match.

How long do Thai micro crabs live?

Unfortunately, these crabs are not all too long-lived. Their lifespan is usually around a year and a half.

Buying Thai micro crab

Thai micro spider crabs are still relatively new in the aquarium hobby. Although some aquarium stores seem to have caught on not everyone sells them yet.

The Shrimp Farm sells Thai micro spider crabs with live arrival guarantee and ships them right to your doorstep for a low flat shipping rate. You can order your crabs here!

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HYMENOSOMATID, T. N. S. O. PRELIMINARY DESCRIPTIONS OF ONE NEW GENUS AND THREE NEW SPECIES OF HYMENOSOMATID CRABS FROM SOUTHEAST ASIA (CRUSTACEA: DECAPODA: BRACHYURA).

Ng, P. K. (2007). On the taxonomy of the genus Hymenicoides Kemp, 1917 (Crustacea: Decapoda: Brachyura: Hymenosomatidae), with resurrection of Limnopilos Chuang & Ng, 1991, and descriptions of two new species.

Patoka, J., Bohatá, L., Karella, T., Marková, J., Yuliana, E., & Yonvitner. (2019). Invasive potential of pet-traded pill-box crabs from genus Limnopilos. Diversity, 11(6), 91.