Blue Eye Long Spine Urchin [Diadema savignyi]

The Blue Eye Long Spine Urchin (Diadema savignyi) is an effective, nocturnal algae grazer suitable for mature, large marine tanks (30+ gallons) with stable water conditions, pH 7.7–8.5, SG 1.023–1.026). It requires ample algae for grazing but may need supplemental seaweed if food is scarce. Caution is needed as they are "bulldozers" that can topple unanchored rockwork. 

Care Requirements

Diet: Primarily herbivorous; they graze on algae and coralline algae. If natural algae is insufficient, they must be fed dried seaweed/algae sheets.

Reef Safe: Considered reef-safe, but their active grazing can sometimes annoy or damage delicate corals, and they may consume coralline algae.

Tank Setup: Requires a large, established aquarium (30+ gallons) with plenty of live rock for grazing and hiding during the day.

Water Parameters: Highly sensitive to copper-based medications and high nitrates.

Handling: Use caution, as their long, thin spines can break off in the skin, causing pain. 

Behavior & Compatibility

Nocturnal: Usually hides in caves or crevices during the day, emerging at night.

Tank Mates: Compatible with most fish, but avoid large, aggressive predators that prey on urchins, such as triggerfish and large wrasses.

Movement: Known to move large items (rock/frags) while foraging. 

These urchins are excellent for keeping algae in check and are often considered a staple of a mature reef cleanup crew, provided their, at times, disruptive nature is managed.