Cubaris sp. "Rubber Ducky"
A striking yellow-and-grey isopod from Southeast Asia — beautiful but demanding, and not the beginner species some sellers claim.
About this species
Cubaris sp. "Rubber Ducky" is a cave-dwelling isopod originally collected from limestone caves in Thailand. Its distinctive yellow head and segmented grey body have made it one of the most sought-after species in the hobby. Like all isopods, it is a terrestrial crustacean that breathes through gill-like pleopods — desiccation is the primary killer.
Be honest with yourself about this species: it is not a beginner isopod despite its appeal and despite what some online sellers suggest. Rubber Duckies need stable tropical conditions with high humidity and excellent ventilation simultaneously — a combination that takes experience to maintain. They breed slowly, tolerate little environmental fluctuation, and die quickly when conditions slip.
Enclosure
A well-sealed enclosure with controlled ventilation is essential. Use a plastic tub with a tight-fitting lid and small ventilation holes — enough airflow to prevent stagnation but not so much that humidity drops. Many keepers use modified food containers or specialist isopod tubs. Include limestone or calcium-rich rock to mimic their natural cave habitat.
Provide plenty of cork bark hides and leaf litter. Sphagnum moss helps maintain humidity. Keep the enclosure away from direct sunlight and temperature swings.
Substrate
Cubaris species benefit from a calcium-rich substrate:
- 50% coco coir
- 20% organic topsoil
- 15% crushed limestone or calcium powder
- 15% sphagnum moss
The substrate should be consistently moist but never waterlogged — think wrung-out sponge. Depth of 5–8 cm. Top with oak or beech leaves and pieces of sphagnum moss. Never use softwood (pine, cedar) in any form — it is toxic to isopods.
Feeding
- Dried hardwood leaves (oak, beech) — primary food
- Cuttlefish bone — critical for calcium; leave in the enclosure permanently
- Small amounts of vegetable: courgette, carrot, sweet potato
- Protein once weekly: dried shrimp, fish flakes
- Bee pollen — many Cubaris keepers report good results as a supplement
Remove uneaten fresh food within 24–48 hours. Mould growth can be fatal in the enclosed, humid conditions Rubber Duckies need.
Breeding
Rubber Duckies breed slowly compared to Porcellio or Armadillidium species. Females carry small broods in their marsupium, and new mancae appear infrequently — expect a few young every couple of months at best. Do not disturb the colony or substrate unnecessarily. Building a colony takes patience; starting with at least 10–15 individuals improves your odds of establishing a breeding group.
Common mistakes
- Buying too few — starting with 5 or fewer often results in colony failure
- Treating them like Porcellio scaber — they need fundamentally different conditions
- Letting humidity drop below 70% — their pleopods dry out and they suffocate
- Poor ventilation despite high humidity — stagnant, wet air breeds mould and bacterial issues
- Temperature swings — a stable 22–26°C is far more important than hitting exact numbers