TankBud

Red knob sea star

Protoreaster linckii

Also known as African Sea Star, African Red Knob Sea Star, Red Spine Star, Red Knob Starfish

SaltwaterInvertebrate

Red knob sea star (Protoreaster linckii)
Diego Delso · CC BY-SA 4.0

Care at a glance

Temperature
75–81°F
24–27°C
pH
8.1–8.4
Adult size
11.8 in
30 cm
Minimum tank
53 gal
200 L
Temperament
Peaceful
Social behavior
Solitary
Swim level
Bottom
Difficulty
Easy
Breeding
No record
Rarity
Common
Reef safe
Not reef safe
Family
Oreasteridae
Origin
western Indian Ocean, along the East African coast and Madagascar, north to India and Sri Lanka

Overview

Not reef safe: as it grows it becomes an active predator of soft corals, sponges, tube worms, clams, and even other sea stars, so like its chocolate chip relative it is strictly a fish-only-with-live-rock animal, never a reef tank one. Small juveniles graze more on algae and biofilm and can look deceptively harmless, but that does not last, since the same animal turns predatory as it matures. Feed it chopped clam, shrimp, squid, or fish once or twice a week; it scavenges the rest of the time and will not go hungry between meals. Use a slow drip acclimation and keep salinity and pH stable during introduction, since like every sea star here it is intolerant of sudden water chemistry swings even though it is otherwise a tough, easygoing animal once established.

In the wild

Found along the western Indian Ocean, mainly the East African coast and Madagascar, north to India and Sri Lanka, with a small isolated population off Western Australia, on sandy and muddy seabeds from shallow tidal pools down to about 100 m. It forages slowly over open bottom day and night, so it needs a soft sand substrate to move across plus enough floor space that it is not constantly climbing over rockwork or other tankmates. A tank of at least 200 litres (53 US gal) suits one of these large, heavy-bodied stars long term.

Good to know

Easy to tell apart from other large sea stars by its thick gray body and the rows of bright red, knob-like tubercles running along each of its five arms, connected by thin red lines into a pattern that looks almost like a wired grid. It belongs to family Oreasteridae, the cushion stars, alongside the chocolate chip star, and grows into one of the largest sea stars in the hobby at up to about 30 cm across. Wild populations are also collected and dried for the curio trade, particularly in Tanzania, where mummified specimens are sold as souvenirs.

Did you know

Despite its armor-plated look, it is a slow enough mover that it can end up prey itself: large triggerfish and pufferfish are known to flip and eat sea stars in the wild, part of why FOWLR tanks built around those fish are a poor match for it.

Common questions

What size tank does a Red knob sea star need?

A Red knob sea star needs at least 53 gal (200 L). It spends most of its time in the bottom.

What temperature and pH does a Red knob sea star need?

A Red knob sea star is comfortable at 75–81°F (24–27°C) with a pH of 8.1–8.4.

How big does a Red knob sea star get?

An adult Red knob sea star reaches about 11.8 in (30 cm).

Related species