Long-Spined Urchin
Diadema setosum
A reef-grazing urchin with impressively long spines and a sharp sense of self-defense.
About
The long-spined urchin (Diadema setosum) is one of the most recognizable echinoderms in the Indo-Pacific, ranging from the Red Sea across to the South Pacific islands and Japan, and even showing up as an introduced species in the Mediterranean. In the wild it occupies shallow reef environments from the surface down to considerable depths, where it plays a genuinely useful role as an algae grazer, keeping growth in check on live rock and reef structures. In the aquarium, it delivers that same service. A mature specimen will work its way methodically across rockwork and glass, rasping away unwanted algae. The spines are the first thing anyone notices, dramatically long relative to the body, and they are not just for show. This urchin can detect the approach of tank mates and will pivot its spines toward anything it perceives as a threat, so keeping it with curious or nippy fish is asking for trouble. And careless hands during maintenance will regret the encounter. Being nocturnal, it tends to tuck into crevices during daylight and becomes more active once the lights go down. It is a reasonable choice for a hobbyist with some reef-keeping experience who can provide a suitably sized system and exercise a bit of care during tank maintenance.
Similar species
Other invertebrate you might consider
From the same region
Share the same natural habitat. Great for a biotope-themed tank
Frequently asked questions
- How big does the Long-Spined Urchin get?
- The Long-Spined Urchin reaches about 8–10" as an adult.
- What size tank does the Long-Spined Urchin need?
- A minimum of 55 gallons is recommended for the Long-Spined Urchin.
- What water parameters does the Long-Spined Urchin need?
- The Long-Spined Urchin does best with a temperature of 72–82°F, a pH of 8–8.4.
- Is the Long-Spined Urchin aggressive?
- The Long-Spined Urchin is semi-aggressive. It can work in a community with careful tankmate choices and enough space.
- What does the Long-Spined Urchin eat?
- The Long-Spined Urchin is a herbivore. It needs a plant-based diet such as algae, blanched vegetables, or spirulina-based foods.
- How long does the Long-Spined Urchin live?
- With good care, the Long-Spined Urchin typically lives 3-5 years.
- Is the Long-Spined Urchin reef safe?
- The Long-Spined Urchin is generally considered reef safe.