Crabby Isopods (Giant Nguyen) Care Guide

The Crabby is one of the largest Cubaris available in the UK, and one of the few premium species whose appeal survives being photographed badly. It is broad, deep orange, flared with pale yellow down each side, and substantial enough that you spot it the moment you lift a piece of cork. It is also scarce, expensive and sold under two different names, which is why people struggle to find it.

Quick answer

Crabby Isopods are an undescribed Cubaris from the limestone cave systems of southern Vietnam, also sold as Giant Nguyen. Adults are among the largest Cubaris in the hobby. They want 22 to 27°C, high and steady humidity of 70 to 80%, deep calcium-rich substrate and genuine airflow. They breed slowly, they are a poor first Cubaris, and in the UK they typically sell around £120 for a starter group.

One animal, two names

You will meet this species as the Crabby and as the Giant Nguyen, and both refer to the same undescribed Cubaris. European keeper circles tend to use Giant Nguyen; UK retail more often uses Crabby, a nod to the broad, flared, faintly crab-like outline. Listings shorten these variously to Crabby Isopod, Cubaris sp. 'Crabby' and Cubaris sp. 'Giant Nguyen'.

This matters practically rather than academically. Availability is thin, stock surfaces under whichever label the seller prefers, and if you search only one name you will miss half the listings in the country.

Appearance and size

The colour reads first: a rich orange-red across the back, edged with pale yellow flaring down each side. Against dark substrate and brown leaf litter that contrast is what makes the species a display animal rather than a collector's curiosity.

The build is the other half of it. Where most Cubaris are neat and compact, the Crabby is broad-shouldered and visibly heavy, and mature animals have real physical presence in an enclosure. Disturbed, one shuts into a solid orange marble the way all Cubaris do, then unrolls in its own time once it decides the coast is clear.

Where it comes from, and why that governs the care

It is a limestone cave animal from southern Vietnam, and almost everything sensible about keeping it follows from that.

There is no published physiology for Cubaris. No thermal preferendum, no measured water-loss rate, nothing. The literature on terrestrial isopods rests on roughly six temperate and Mediterranean species, so every number quoted for a cave Cubaris in this hobby, ours included, is an extrapolation. We would rather say that plainly than publish confident figures we cannot support.

What we can lean on is the habitat itself, which has been measured. McClure, Lim and Winn (1967, Pacific Insects 9(3)) recorded terrestrial isopods in Dark Cave at Batu Caves, Malaysia: the cave interior averaged 24.5°C with a monthly range of 23.0 to 25.0°C, while the surface outside reached daily maxima of 28.8 to 30.3°C. Tropical cave humidity has been measured at a mean above 97%, with the deepest passages saturated.

Two things follow. A cave is not hot, it is stable - its whole annual swing was around two degrees, smaller than the surface managed in a single day. And a cave is wet throughout, which is why cave Cubaris are the one group where we do not insist on a genuinely dry end in the enclosure. For everything else in our range, a moisture gradient needs a dry end below 65% or the animals cannot detect it at all. Cave species are the documented exception.

Care

Temperature

Hold 22 to 27°C, and prioritise steadiness over the exact figure. Swings are what cost people colonies with this species. In most UK homes that means supplementary heat for part of the year, on a thermostat, and no heat at all through a warm summer - see our guide on how hot is too hot, because a British July can now push a closed room past the top of that band without any help from you.

Humidity and airflow

High and steady, around 70 to 80%, balanced against real airflow rather than sealed in. Damp like a wrung-out sponge, never wet. If you are unsure, run slightly drier and open up the ventilation: stagnant saturated air causes far more losses in this group than a slightly dry tub does.

Cross-ventilation through mesh set into two opposing walls works better than a single vent, because it moves air through the box rather than letting it sit.

Substrate

Give them depth to burrow, around 15 cm. The base wants to be nutritious as well as moisture-retentive: flake soil, white-rotted hardwood and organic topsoil, with crushed limestone worked all the way through rather than sprinkled on top. A large, heavily calcified isopod needs calcium constantly available, not offered occasionally.

Coco coir is the usual shortcut and we would leave it on the shelf. It holds water beautifully and feeds nothing.

Pack the surface with hardwood leaf litter, cork flats and tubes, and a few limestone chunks for cover.

Skip the water dish

Misting and a permanently damp corner cover everything they need. Standing water invites drownings, particularly of mancae, and adds nothing a damp substrate does not already do.

Should you buy one?

Suitable for: keepers with a season or two of Cubaris experience, collectors who want size and colour in one animal, and anyone with a stable warm room and the patience for slow breeding.

Not suitable for: a first isopod, or a first Cubaris. At this price the cost of learning on them is high, and the things that go wrong - swings in temperature, a sealed humid box, thin substrate - go wrong slowly and are hard to reverse once a small colony has stalled. Start with something forgiving and work up. Our Dairy Cow guide is a better first stop, and the Cubaris care guide covers the group properly.

Buying one in the UK

Availability is the real constraint. This is a recent arrival, colonies are slow to build, and stock appears and vanishes. A few practical points:

• Search both names. Crabby and Giant Nguyen will surface different listings.
• Expect around £120 for a starter group in the UK. Substantially cheaper usually means either a very small count or a misidentified animal.
• Buy captive-bred. Everything we sell is UK-bred, which matters more for a species this scarce than for a common one.
• Check the count and the guarantee. We add 20% over the number you pay for and guarantee live arrival.
• Order early in the week. We post Monday to Thursday so nothing sits in a depot over a weekend, and in hot or freezing weather we hold shipments rather than risk them.

Browse Crabby Isopods, or see the full Cubaris collection.

Frequently asked questions

Are Crabby and Giant Nguyen the same isopod? Yes. Two trade names for the same undescribed Cubaris from southern Vietnam. Neither is more correct than the other, because the species has never been formally described.

How big do they get? They are among the largest Cubaris in the hobby, and noticeably broader than typical species in the group. Individual size varies with conditions and age, and we would rather not publish a precise figure we have not measured across a decent sample.

Do they need a heat mat? For part of the UK year, usually yes, on a thermostat. Through a warm summer, no. The band you are aiming for is 22 to 27°C and a modern sealed room can exceed that unaided.

Why are they so expensive? Scarcity and slow breeding. They arrived in the UK recently, colonies build slowly, and demand for large colourful Cubaris is high. Price tracks availability rather than difficulty.

Can I keep them with other isopods? We would not. One species per enclosure is the safer rule generally, and at this price the risk of a faster-breeding species outcompeting them is not worth taking.