Diadema setosum
Source: Oceanreef.dk - Kasper Hareskov Tygesen
Diadema setosum
Source: JJPhoto.dk
Diadema setosum
Source: JJPhoto.dk


Latin name Diadema setosum
Common name Long-spined sea urchin
Family Echinoidea - Diadema
Origin East Indian Ocean, Australia, Indonesia, East Pacific, Central/West Pacific
Max length 60 cm (23.6")

As aquarium fish

Minimum volume 200 l (53 gal)
Hardiness Average
Suitable for aquarium Suitable for most aquarium
Reef safe Always reef safe
Aggressiveness Peaceful


  • Microalgae (Eg. spirulina)
  • Macroalgae (Eg. seaweed / nori)

Overturns corals

This species will overturn pieces of corals and corals which are not fully attached. 

Effective algae-eaters

This species can eat large amounts of algae (relative to their size) from rocks, like green hair algae and filamentous algae.

As it doesn’t eat every algae type, in case of a specific algae plague, find out more precise information.

Family description (Echinoidea)

Sea urchins are often used to keep various algae at bay. 

They are very effective algae eaters, and will eat anything from coralline algae to green hair algae.
Sea urchins must not be kept in an aquarium with few algae, as they may starve to death. 

Sea urchins should be acclimatized slowly, due to sensitivity towards changes in salinity.

References and further reading

About references

Diadema setosum - Wikipedia - (English)

Ronald L. Shimek. 2004. Marine Invertebrates (PocketExpert Guide) - TFH Publications / Microcosm Ltd. - (English)
Ronald L. Shimek. 2003. Sea Urchins, A Testy Subject - Reefkeeping Magazine - (English)
Bob Fenner. Some Spines Now! Sea Urchins (and Sand Dollars), the Echinoids, Pt. 1, Pt. 2 - Wet Web Media - (English)


algae eater, destructive, herbivore
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