This is from Baensch's Marine Atlas, Vol. 3, p. 942. It describes
Astropecten phragmorus, which is apparently very similar to A.
polyacanthus. I've included all of the information that they provide
(except for availability and difficulty). Hope this helps. :-)

Habitat: Indo-Pacific; from the Red Sea to the Philippines. It lives
at depths of 5-25 m.

Sexual Differences: None

Social Behaviour/Association: This solitary animal usually remains
buried in the substrate during the day,
but at twilight it emerges and freely
roams through the night searching for
food on coralline sands and close to
reefs. Keep singly; it cohabits well
with fishes that do not sleep on the
bottom.

Maintenance: An aquarium with a 5-10 cm layer of sand where it [likes]
to burrow. Rock and coral edifications do not influence
maintenance.

Light Requirement: Sunlight zone (30,000 to 50,000 lux)

Breeding/Reproduction: Like other Astropecten

Feeding: Carnivore; inhabitants of the upper sand layer are "sniffed
out", dug up, and then stuffed into the elastic stomach. The
small bivalves it consumes with predilection can be offered
in captivity.

Specialties: Characteristically, this sea star is beige, brown, to
pink and often has dark irregular spots and several rows
of large teeth on the edges of the arms. Near the base
of the arms, there is a light to dark brown or reddish
line. Astropecten polyacanthus is extremely similar, but
its erect rows of spines are internally noncontinuous.

Temperatu 22dC - 27dC

Diameter: 15cm

Tank Length: from 50cm

Water Movement: moderate

Water Region: bottom



In article , says...
Acording to the Livequaria.com description, Astropecten polycanthus
do not have suction cups so they cannot climb glass/rocks. I am not
sure if Liveaquaria is right or wrong, but my star has suction cups and
does climb glass. Maybe I have something different, not Astropecten
polycanthus? I am currently trying to identify mine because since I put
it into the tank the substrate is dead-clean. No benthic animals whatsoever.
And before putting it in I have quite a live sand with a lot of miniature
brittle stars, copepods and other live forms. Now it is dead-dead.
I tried to feed my star recently to prevent it from eating critters form
the bottom of the tank but it just ignores completely chunk of shrimp meat
put underneath it and just walks away. Maybe not hungry anymore?
Or maybe not guily of this carnivore job?
If you can - please help me identify - you will find pictures he
www.polbox.com/p/pszemol/english.html - click on Sand Sifting Star.
If you have good marine invertebrate atlas, please check if Astropecten
polycanthus has suction cups or not... and what does it eat for real...
Thanks!


--
7y FW -- 33g & 55g
100 gallon reef-ready air tank. (Converting to reef)