Description
Yellow Cucumber (Colochirus robustus)
(Also known as the Yellow Sea Cucumber or Yellow Filter-Feeding Cucumber)
Overview
The Yellow Cucumber (Colochirus robustus) is a vibrant, compact sea cucumber prized for its bright yellow to golden-orange body and delicate, feather-like feeding tentacles. Growing to around 10–12 cm (4–5 inches), this species adds movement and colour to the reef aquarium while acting as a natural filter feeder. It belongs to the same genus as the Candy Cucumber (Colochirus crassus), sharing similar care requirements. Although peaceful and reef safe, it requires regular feeding with suspended planktonic foods and stable conditions to thrive long-term.
Origin
Native to the Indo-Pacific region, including Indonesia, the Philippines, and the Great Barrier Reef. Commonly found on reef slopes and lagoon areas with moderate current, where it extends its feeding tentacles to catch plankton from the water column.
Feeding
The Yellow Cucumber is a suspension feeder, filtering microscopic food from the water using its feathery oral tentacles. In aquariums, natural plankton levels are often too low, so supplemental feeding is essential:
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Live or concentrated phytoplankton (primary food source)
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Marine snow and zooplankton blends
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Fine powdered coral foods or microalgae (e.g. Reef-Roids, Reef Energy)
Feed 3–5 times per week, ideally by gently target-feeding near the tentacles with a pipette or turkey baster. Consistent feeding is crucial for long-term survival.
Water Flow
Moderate, indirect flow. Enough movement to deliver planktonic food to its tentacles, but not so strong that it prevents feeding or causes retraction. The cucumber should remain stationary in areas of steady but gentle current.
Lighting
Low to moderate lighting. Non-photosynthetic; lighting is irrelevant beyond providing natural day-night cues and supporting other reef life. Prefers shaded or partially lit areas under rock overhangs or coral branches.
Placement
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Position on rockwork or stable substrate in a moderate flow zone where it can anchor securely.
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Ensure powerheads, wavemakers, and overflows are covered with guards to prevent injury or suction accidents.
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Avoid unstable or high-traffic areas of the tank where it could be disturbed during feeding.
Tank Mates
Peaceful and fully reef safe. Compatible with:
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Clownfish, gobies, blennies, and small wrasses
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Reef-safe shrimp, crabs, and snails
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All types of corals and filter-feeding invertebrates
Avoid:
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Predatory fish (triggers, puffers, large wrasses)
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Aggressive or overly active tank mates that may disturb its feeding behaviour
Aggression
Completely peaceful. Like other sea cucumbers, Colochirus robustus may release mild toxins (holothurin) if stressed, injured, or dying. This is rare in stable reef aquariums but can be serious if it occurs. Handle gently, provide stable water quality, and ensure good oxygenation to prevent stress.
Experience Level
Advanced. Though peaceful and reef safe, it is a delicate filter feeder that depends on frequent feeding and pristine, stable water conditions. Best suited to mature reef systems with established plankton populations and experienced aquarists comfortable with target feeding.
Water Parameters
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Temperature: 24–27°C (75–81°F)
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pH: 8.1–8.4
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Salinity: 1.024–1.026 SG
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Hardness (dKH): 8–12
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Nitrate: <10 ppm
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Tank Size: Minimum 75 gallons (280L) for stability and adequate feeding opportunities
Maintain excellent water quality and gentle, consistent flow. Avoid rapid changes in temperature, pH, or salinity.
Reef Compatibility
Reef safe. Will not harm corals, fish, or invertebrates and contributes to the biological filtration of the aquarium by removing fine organic matter from the water. Ideal for peaceful, plankton-fed reef systems.
