Short Spine Urchin - (No Online Purchases)

The Short Spine Urchin (also called the collector urchin or sea egg) is a popular marine aquarium species because of its peaceful nature and algae-grazing habits. Here’s a concise care guide using Australian spelling.

Overview

• Scientific name: Tripneustes gratilla
• Common names: Short Spine Urchin, Collector Urchin
• Origin: Indo-Pacific reefs
• Maximum size: Around 10–15 cm diameter
• Temperament: Peaceful
• Reef safe: Generally yes, though may move loose corals or decorations
• Difficulty: Moderate

Aquarium Requirements

Tank Size

• Minimum 200 litres
• Larger systems are more stable and provide more grazing area

Water Parameters

• Temperature: 24–27°C
• Salinity: 1.024–1.026 SG
• pH: 8.1–8.4
• Alkalinity: 8–12 dKH
• Calcium: 380–450 ppm
• Magnesium: 1250–1350 ppm
• Ammonia/Nitrite: 0
• Nitrate: ideally under 10 ppm

Urchins are highly sensitive to sudden parameter swings, especially salinity and pH.

Diet

The Short Spine Urchin is mainly an algae grazer.

Feeds on:

• Film algae
• Hair algae
• Coralline algae
• Seaweed sheets (nori)
• Algae wafers

Supplement feeding is important once natural algae becomes limited.

Behaviour

• Mostly nocturnal but often visible during the day
• Known for carrying shells, rubble, or coral frags on top of its body as camouflage
• Excellent cleaner for algae control
• Can dislodge unsecured rocks or corals

Compatibility

Generally compatible with:

• Reef fish
• Corals
• Snails
• Shrimp
• Other peaceful invertebrates

Avoid:

• Triggerfish
• Large wrasses
• Pufferfish
• Predatory crabs

These may nip at or attack the urchin.

Important Care Notes

• Acclimate slowly using drip acclimation
• Never expose to air for extended periods during transfer
• Stable calcium and alkalinity are essential for spine and shell health
• Ensure rockwork is secure

Signs of Stress

Watch for:

• Dropping spines
• Lack of movement
• Fading colour
• Detached tube feet

These often indicate poor water quality or starvation.

Lifespan

With proper care, Short Spine Urchins can live 5–10 years or longer in a well-maintained marine aquarium.