TankBud

Indo micro crab

Neorhynchoplax prima

Also known as Java giant micro crab, False spider crab, N. Rhynchophylla prima

FreshwaterCrab

Indo micro crab (Neorhynchoplax prima)

Care at a glance

Temperature
72–82°F
22–28°C
pH
6.5–7.8
Adult size
0.4 in
1 cm
Minimum tank
5 gal
20 L
Temperament
Peaceful
Social behavior
Social
Tankmates
With caution
Swim level
Bottom
Difficulty
Medium
Breeding
No record
Rarity
Very rare
Family
Hymenosomatidae
Origin
Bintan and Bangka islands, Indonesia

Overview

A peaceful, nearly invisible picker that sits in moss and root tangles combing biofilm and tiny particles off surfaces, best kept as a group of half a dozen or more so you actually see one now and then. It has no way to hurt a tank mate and is itself easy prey, so pair it only with dwarf shrimp, small snails, and nano fish that leave shrimp fry alone. Feed powdered fry food, crushed flakes, and a little frozen baby brine shrimp, and let the tank grow biofilm. Keep the water stable and the flow gentle, and never treat the tank with copper.

In the wild

The Indo micro crab was described from Pengudong on Bintan, the Indonesian island just south of Singapore. Ng and Chuang's 1996 description calls it a freshwater species, the first freshwater member of its genus found in Sundaland, and it is also known from Bangka Island off Sumatra. The marine species register flags it marine by default, which the description contradicts, so keep it in fresh water like the Thai micro crab, stable and mature above all. Give a group a tank of 20 liters or more with moss, fine leaf litter, roots, and a gentle filter, at 22 to 28 C and pH 6.5 to 7.8. It lives in and on the plants, not on open sand.

Good to know

Neorhynchoplax prima is a false spider crab in the family Hymenosomatidae, one of eight species that Ng and Chuang described as new in their 1996 revision of the Southeast Asian members of the family. The holotype is a male 6.8 by 5.7 mm, so the whole crab is smaller than a fingernail, a flat disc of a body on long thin legs, and it is a giant only next to the Thai micro crab. Nothing is published on its larvae, and there is no record of it breeding in captivity, so every crab in the trade is wild collected. Its name is simply Latin for first.

Did you know

One shop lists the same species twice, as the Indo micro crab and, at a higher price, the Java giant micro crab. Both are Neorhynchoplax prima, a crab described from Bintan, an island next to Singapore and a long way from Java.

Common questions

What size tank does an Indo micro crab need?

An Indo micro crab needs at least 5 gal (20 L). It spends most of its time in the bottom.

What temperature and pH does an Indo micro crab need?

An Indo micro crab is comfortable at 72–82°F (22–28°C) with a pH of 6.5–7.8.

How big does an Indo micro crab get?

An adult Indo micro crab reaches about 0.4 in (1 cm).

Related species