CoralSaltwaterIntermediate

Lesser Starlet Coral

Siderastrea radians

Also known as: shallow-water starlet coral, starlet coral

A compact, tough starlet coral that sometimes rolls free like a living stone.

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About

The lesser starlet coral (Siderastrea radians) is a small but hardy massive coral found on shallow reef environments, where it tends to stay modest in size. Colonies rarely exceed about 30 centimeters across. What makes this species genuinely interesting is that some colonies become free-living, detaching from the substrate and slowly rolling around as rounded balls, essentially mobile lumps of living reef. Up close, the surface is covered in small rounded corallites, each roughly two and a half to three millimeters across, sitting deep within the skeletal structure. The septa are arranged in three distinct cycles, giving the surface a neat, organized look when you examine it closely. Coloration is understated, uniform light browns without much variation, so this is not a coral you keep for flashy pigmentation. Its appeal lies more in its interesting growth forms and its reputation for being reasonably tough compared to many SPS corals. It fits well into a reef system with good light and moderate water movement, and while it is not the easiest coral for a complete beginner, an intermediate keeper with a stable, established reef setup should find it a manageable and rewarding addition.

At a glance

Type: Coral
Water: Saltwater
Origin: Shallow reef.
Reef safe: Yes
Lighting: High
Flow: moderate

Care guide

Provide high-intensity lighting and moderate water flow in an established reef tank with stable parameters. Position on the rockwork or substrate where it receives good light penetration but is protected from excessive surge. Feed occasionally with fine plankton or coral-specific supplements, though this species relies heavily on photosynthesis. Monitor for tissue recession at the base, which can indicate poor flow or lighting. Avoid sudden changes in water chemistry or flow patterns. Some colonies naturally detach and roll. This is normal behavior, not distress. Ensure adequate calcium and alkalinity for skeletal growth. Avoid allelopathic corals nearby, as competition can stress the colony.

Breeding

Siderastrea radians spawns during specific seasonal periods, releasing gametes into the water column like many stony corals. Captive spawning occurs occasionally in established reef tanks but is difficult to control or document reliably. Fragging is possible by carefully cutting stable branches or sections with a diamond saw and allowing the cut edges to heal under strong light and flow. Success rates vary; provide excellent water conditions during recovery. Natural fission and daughter colony formation may occur in undisturbed, healthy specimens over time.