Thai micro crab care guide
Also called: Micro crab, Thai micro spider crab, False spider crab, Pill-box crab
The Thai micro crab is a tiny, fully aquatic crab with a body about 0.4 inches (1 cm) wide and long, hairy legs. It is peaceful and fits nano tanks with shrimp, but it is shy, short-lived, sensitive to poor water and easily eaten by bigger fish.
Thai micro crabs need a tank of at least 5 gallons (19 L), a group of 5 or more, and water at 22–27°C (72–81°F) with a pH of 6.5–7.5. They grow to about 1 cm (0.4 in) and are peaceful.
Plan a tank with Thai micro crabsSee all tank mates
Thai micro crab quick facts
| Scientific name | Limnopilos naiyanetri |
|---|---|
| Family | Hymenosomatidae |
| Origin | Tha Chin River, central Thailand, among the roots of floating water hyacinth (almost all are wild-caught) |
| Adult size | 1 cm (0.4 in) |
| Minimum tank | 5 gallons (19 L) |
| Temperature | 22–27°C (72–81°F) |
| pH | 6.5–7.5 |
| Hardness (GH) | 4–12 dGH |
| Group size | 5 or more (group) |
| Temperament | Peaceful |
| Swims at | Bottom |
| Diet | Omnivore |
| Care level | Moderate |
| Lifespan | 1–1.5 years |
| Safe with plants? | Yes |
Tank setup
A group of five or six can live in a well-planted 5-gallon (19 L) tank, though 10 gallons (38 L) stays more stable. Give them moss, dense plants, floating plant roots and small caves. A sponge filter is ideal, and any other intake needs a foam cover. They are fully aquatic and don't need land.
How many Thai micro crabs in a tank?
The smallest common tank that suits Thai micro crabs is a 5 gallon. Here is roughly how many fit in each size when they are the only fish, based on adult size and waste output. Leave room if you want tank mates.
| Tank | Thai micro crabs (alone) |
|---|---|
| 3 gallon | Too small |
| 5 gallon | 5–363 |
| 10 gallon | 5–726 |
| 15 gallon | 5–1090 |
| 20 gallon | 5–1453 |
| 20 gallon long | 5–1453 |
| 29 gallon | 5–2107 |
| 40 gallon | 5–2907 |
| 55 gallon | 5–3997 |
| 75 gallon | 5–5450 |
| 125 gallon | 5–9084 |
What you need for Thai micro crabs
Sized for a 5 gallon tank, the smallest common size that suits a group of 5 Thai micro crabs. For a different tank or a mix of fish, use the stocking calculator for a list sized to your plan.
Tank and equipment
- 5 gallon aquarium (tank or kit) (opens Amazon in a new tab)Bigger tanks are more stable and easier for beginners. How to choose
- Adjustable heater, 25 W (opens Amazon in a new tab)Holds about 76 °F (24.5 °C) in a room at 68 °F (20 °C). A bigger heater can overheat a small tank if it sticks on. How to choose
- Aquarium thermometer (opens Amazon in a new tab)Check it daily: heaters can fail stuck on or off. How to choose
- Sponge filter for 10 gallons (opens Amazon in a new tab)Gentle flow, about 15–25 GPH, suits shrimp and snails, which prefer slow water. Needs a small air pump. How to choose
- About 15 lb of aquarium gravel (opens Amazon in a new tab)Enough for a layer about 2 in (5 cm) deep. Smooth gravel suits most community fish. How to choose
- Water conditioner (dechlorinator) (opens Amazon in a new tab)Removes chlorine and chloramine from tap water. Seachem Prime is a popular, concentrated choice. How to choose
- Liquid test kit (ammonia, nitrite, nitrate, pH) (opens Amazon in a new tab)Liquid kits are more accurate than strips. The API Freshwater Master Test Kit is the common choice. How to choose
- Gravel vacuum (siphon) (opens Amazon in a new tab)Cleans the gravel and does the water change in one go. How to choose
- LED aquarium light, about 16 in long (opens Amazon in a new tab)Match the light to the tank length. Basic LEDs grow easy plants. How to choose
Food and extras for Thai micro crabs
- Sinking pellets or wafers (opens Amazon in a new tab)Bottom feeders need food that reaches the floor.
- Caves and hides (opens Amazon in a new tab)Gives shy and territorial fish their own space.
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Water parameters
Keep them at 22–27 °C (72–81 °F), pH 6.5–7.5 and 4–12 dGH. Stability matters more than exact numbers, so avoid sudden swings in temperature or chemistry. Only add them to a mature, cycled tank, keep nitrate low and never use copper.
Best tank mates for Thai micro crabs
These popular species share Thai micro crabs' water needs and temperament. See the full list of 71 good matches.
Cherry shrimp
3 cm (1.2 in) · 20–27°C (68–81°F)
Nerite snail
2.5 cm (1 in) · 22–27°C (72–81°F)
Guppy
5 cm (2 in) · 22–27°C (72–81°F)
Neon tetra
3.5 cm (1.4 in) · 21–25°C (70–77°F)
Panda corydoras
4.5 cm (1.8 in) · 21–25°C (70–77°F)
Bristlenose pleco
12 cm (4.7 in) · 22–26°C (72–79°F)
Bronze corydoras
7 cm (2.8 in) · 21–26°C (70–79°F)
Zebra danio
5 cm (2 in) · 18–25°C (64–77°F)
Avoid keeping Thai micro crabs with
- Discus: They need different temperatures: Thai micro crab 22–27°C (72–81°F), discus 28–30°C (82–86°F).
- Pea puffer: Pea puffer is best kept in a species-only tank.
Feeding
They pick biofilm, detritus and soft algae off plants and moss, and also catch fine particles with the hairs on their legs. Feed powdered shrimp food, crushed algae wafers or small frozen foods such as daphnia a few times a week. Many keepers add a calcium source for molting.
Behavior
Very peaceful and shy. They hide by day and come out after dark, and several often share one hiding spot. They ignore fish and adult shrimp but may pick at tiny shrimplets. Any fish big enough to swallow them will, so keep only tiny peaceful fish, and avoid crayfish and other crabs.
Breeding
Females carry small eggs under the tail flap and release swimming larvae. Keepers have hatched larvae, but none have been raised to adults in home aquariums so far. Plan on buying new crabs rather than breeding them.
Tips from experienced keepers
- Don't use a net. Their legs are fragile. Scoop them out in a cup with some water instead.
- Acclimate slowly by drip. Most are wild-caught and stressed by sudden changes.
- Add plenty of moss and floating plants with roots. They feel safe and feed there.
- Look for them at night with a dim light. By day they hide and are hard to spot.
- A shed shell can look like a dead crab. Check before you panic.
Frequently asked questions
Can Thai micro crabs live with shrimp?
Yes. They are among the best crabs for a shrimp tank. They don't hunt adult shrimp, though they may eat a few very small shrimplets.
Can Thai micro crabs live with a betta?
It's a gamble. Some bettas ignore them, while others hunt them. If you try it, use a heavily planted tank and expect some losses.
Do Thai micro crabs need land?
No. Unlike most pet crabs, they live their whole lives underwater. A normal planted aquarium with no land area is ideal.
Sources
We checked these references when writing this page. Values are for healthy long-term keeping, not survival limits. Last reviewed 2026-10-13. See our editorial policy.