Asterina starfish (Aquilonastra spp.) care guide

Group
Other invertebrates
Other names
Asterina starfish (hitchhiker), Asterina sp., Aquilonastra burtoni, Aquilonastra corallicola, Mini starfish
Family
Asterinidae
Origin
Indo-Pacific and Red Sea; arrives on live rock and frags
Water
saltwater
Maximum size
1.5 cm
Temperature
22–28°C
Temperament
peaceful
Reef safe
with_caution

Care

Asterina starfish are the tiny, pale, often flattened starfish, usually under 1.5 cm, that appear on the glass and rocks of many reef tanks. They mostly belong to the genus Aquilonastra (over 20 species), which was split from Asterina in 2004, so hobbyists still call them asterinas. Most species have five arms, but the ones that split in two (fission) have five to eight arms of uneven length, which is a good identification feature. How it arrives: almost always as a hitchhiker on live rock, rubble or coral frags. Because the fissiparous species reproduce by splitting, numbers can rise quickly when there is plenty of film algae and leftover food. Harmless or not: most asterinas are harmless, helpful grazers of film algae, biofilm and detritus. Some kinds, however, have been seen eating zoanthids, Acropora, Montipora and other coral tissue, especially when numbers are high. Watch them, and if they are eating corals, remove them by hand, trap them, or add a natural predator. Harlequin shrimp eat only starfish and will clear them, but they must then be fed other starfish, so use them only if you can keep them fed. Some wrasses also eat them. They are a common hitchhiker rather than a livestock item, but can be passed on to other reefers who want them. Copper: copper-based medicines and some plant fertilisers are toxic to shrimp, snails and most other invertebrates. Never dose them in a tank holding this animal, and check the label of any treatment or fertiliser before use. Sources: Wikipedia (en.wikipedia.org/wiki/Aquilonastra). Checked October 2026.

Diet

Grazes film algae, biofilm, detritus and leftover food on glass and rock. Some forms graze coral tissue, especially when food is short or numbers are high.

Breeding

Many species reproduce asexually by fission: the starfish splits in two and each half regrows its missing arms, so uneven arms are normal. This is why numbers can boom in the aquarium without any help. Our sources do not describe their sexual reproduction.

Compatibility and tank mates

Reef safe with caution: harmless in most tanks but some populations nip corals (zoanthids, SPS). Eaten by harlequin shrimp and some wrasses. Harmless to fish.

Last updated 8 October 2026. Community-edited care guide on Aquatic-Auctions.

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