Crabby isopods (Cubaris sp. "Crabby," also sold as "Nguyen" or "Giant Nguyen") are widely regarded as the largest Cubaris kept in captivity. They come from caves in Southern Vietnam and are named for their chunky, crab like build and broad golden orange armor. They are a collector species for keepers who value size and rarity, not a species you buy to watch out in the open. This guide covers how to set them up, keep them stable, and get a colony breeding.
Crabby Isopod Quick Facts
- Scientific name: Cubaris sp. "Crabby" (also "Nguyen" or "Giant Nguyen")
- Origin: Southern Vietnam (cave habitat)
- Adult size: Up to about 2.8 cm
- Care level: Intermediate
- Temperature: 70 to 80°F
- Humidity: Moist side kept damp at all times, with a clearly drier side
- Ventilation: Moderate, cross ventilated
- Breeding rate: Slow, small broods
- Activity: Nocturnal and shy, hides under bark, rolls into a ball when disturbed
- Lifespan: Commonly reported at 2 to 3 years
What to Expect From Crabbies
Set your expectations before you buy. Crabbies spend most of their time hidden under cork bark and leaf litter, and they roll into a tight ball when disturbed. You will see them most at night or when you lift a hide. That is normal behavior for this species, not a sign that something is wrong.
They are also slow to build. Sources and keepers agree that a Crabby colony takes months to settle and start producing, and broods are small. If you want a species that is constantly on display, look at our Ember Bees. If you want the biggest Cubaris in your collection, Crabbies are worth the patience.
Enclosure Setup
A 6 to 10 quart tub works for a starter group. Crabbies are big animals, so give a growing colony more floor space over time rather than packing them in. Use cross ventilation (holes or mesh on two opposite sides) so air moves through the bin without drying it out.
Give them 3 to 4 inches of substrate. We use our own ABG style mix in every bin: 12 parts sphagnum moss, 6 parts coco fiber, 4 parts orchid bark, 2 parts charcoal, and 2 parts worm castings. The full recipe is in our ABG substrate guide.
On top of the substrate, add:
- A thick layer of hardwood leaf litter, topped up as it gets eaten
- Decaying hardwood
- Cuttlebone for calcium, available at all times
- A culture of Tropical Pink springtails to keep mold and leftovers in check
Add generous cork bark flats. Crabbies like to wedge under bark pressed against the substrate, and plenty of hides helps a shy colony feel secure.
Humidity and the Moisture Gradient
Like other cave Cubaris, Crabbies want humidity. Keep roughly half to two thirds of the bin damp and let the rest stay drier, so the animals can choose. A clump of damp sphagnum on the wet side helps hold moisture. Mist the damp side when the surface starts to dry, using dechlorinated water.
Published humidity numbers for this species vary, so watch the animals instead of chasing a number. If they all pile on the wettest spot, the bin is too dry. If they all retreat to the driest corner, it is too wet or too stagnant.
Temperature
Normal room temperature works, roughly 70 to 80°F. Avoid long stretches below the mid 60s, which slows breeding, and keep them out of direct sun and away from heaters.
Feeding
Leaf litter and decaying hardwood are their main food and should always be available. On top of that, we rotate small amounts of fish flakes, freeze dried shrimp, and an occasional piece of soft vegetable. Offer a little at a time and remove anything uneaten after a day or two, since leftover food molds quickly in a humid bin.
Keep cuttlebone in the enclosure at all times. A large, heavily armored isopod needs steady calcium to molt cleanly.
Breeding
Crabbies are a slow, patient species. Females carry small broods in a pouch until tiny live young (mancae) emerge. To give a colony the best chance:
- Start with a group of mixed sex adolescents and leave them alone for the first several weeks.
- Keep temperature and moisture stable. Swings stall breeding.
- Keep calcium and leaf litter topped up.
- Avoid lifting every hide to check on them. Constant disturbance stresses a shy species.
A shipped colony usually needs time to settle before it produces. Months, not weeks, is a normal timeline for a new group.
Common Mistakes
- Expecting a display species. Crabbies hide. Judge the colony by health and breeding, not by how many you see.
- Wet and stagnant bins. Moisture without airflow invites mold and mites.
- Letting the whole bin dry out. Keep the damp side damp.
- Skipping calcium. Failed molts often trace back to missing calcium.
- Overfeeding protein. Small amounts, removed promptly.
Common Questions About Crabby Isopods
How big do Crabby isopods get?
Adults reach up to about 2.8 cm, which makes them one of the largest Cubaris in the hobby.
Are Crabby isopods the same as Nguyen isopods?
Yes. Crabby is the trade name used here in the US. The same animal is also sold as Cubaris sp. "Nguyen" or "Giant Nguyen."
Why are my Crabby isopods always hiding?
That is normal. Crabbies are nocturnal and shy, and they spend most of their time under bark and leaf litter. As long as they are eating, molting, and not crowding into one extreme corner, the colony is fine.
How fast do Crabby isopods breed?
Slowly. Broods are small and a new colony can take months to settle. Stable conditions and minimal disturbance help most.
Are Crabby isopods good for beginners?
They are intermediate. The care itself is standard Cubaris care, but their slow breeding and shy nature make them better for keepers who already have a colony or two going.
Where to Buy Crabby Isopods
All Crabby Isopods at Creature Cache are captive bred and ship FedEx Priority Overnight with a 100% live arrival guarantee. Shop Crabby Isopods and pair them with a Tropical Pink springtail culture, or join the Creature Club for restock alerts and 10% off your first order.
More reading: How to Set Up Your First Isopod Enclosure, our ABG substrate recipe, and our springtail care guide.
Questions about your animals? Email us anytime at info@creaturecache.com.