Starfish, also known as sea stars, come in many different colors, patterns, and sizes. There are some amazing-looking species out there, but one of our favorites is this one: the little orange-red biscuit starfish (genus Tosia). Its beautiful, scale-like pattern makes this one a real stunner.
Many starfish have a reputation for being almost impossible to keep alive in the aquarium. Does this also apply to biscuit stars? How do you care for one in your tank? Let’s find out!
| Name (Common, Scientific) | Biscuit starfish, biscuit sea star, Tosia australis, Anchitosia queenslandensis |
| Minimum tank size | 100 gallons |
| Minimum group size | 1 |
| Temperature | 68-72 °F |
| Salinity | 1.023-1.025 |
| pH | 8.1-8.4 |
| Difficulty level | Hard |
What is a biscuit starfish?
Taxonomy
Although the name “biscuit starfish” is used for many members of the large sea star family Goniasteridae, in the aquarium hobby, the name mostly refers to a specific genus in this family called Tosia.
Currently, there are three recognized species of Tosia biscuit starfish:
- Tosia australis
- Tosia magnifica
- Tosia neossia
Of the above, T. australis is the one you’re most likely to stumble upon at your local aquarium store. We haven’t seen the other ones for sale ourselves.
However, there’s another biscuit starfish often kept in the aquarium that we should talk about here: Anchitosia queenslandensis used to belong toTosia, but was moved to its current genus, in which it’s still the only species, in 2007. Many aquarists still refer to it by it as a Tosia, and it’s very similar in terms of looks and care.
This move wasn’t surprising, by the way. Tosia is redefined regularly, and species may be added or removed as scientists untangle the genetic relationships between the different biscuit stars. At one point, there were over ten recognized species, compared to the current three!
In this care guide, we’ll take “biscuit starfish” to mean Tosia australis and Anchitosia queenslandensis.
Did you know? There’s a third sea star that belongs to the same family and is very visually similar to our biscuit stars: Goniaster tessellatus, sometimes called the West African biscuit starfish. However, since this species occurs in different parts of the world and in a different habitat type, its care isn’t the same and we’re not including it here. If your starfish has spikes, then it’s a G. tessellatus, not one of today’s subjects!
Appearance
Their appearance is no doubt what aquarists like most about sea stars of the family Goniasteridae, which also includes such popular aquarium starfish as the red Fromia.
They’re generally colorful, with interesting geometric patterns that look somewhat like rows of differently-sized scales. Biscuit starfish are no exception, and their colors and patterns can be highly varied.
Most of the biscuit starfish for sale for the aquarium are orange or red, with lighter veining between the “scales”. They have short, rounded arms that give them a boxy look, and they’re small. In fact, their maximum diameter of 2″ is about the same as an average biscuit (or cookie in the USA), which explains their common name.
A rainbow of starfish
While Tosia australis is often orange, it can also sport shades of brownish-purple, white, black, and grayish—plus more different patterns than we can count. Anchitosia queenslandensis doesn’t show quite as much variation within the species, but it can range from orange to a bright red.
Scientists figure that the colors and patterns differ between local populations for camouflage purposes, based on the ecological niche the sea stars fill in a location, and depending on the amount of light that penetrates at the depth they inhabit (among, possibly, other reasons).
A sandy substrate, for example, requires different patterns for effective camouflage than a rocky one. Individual stars can’t change color in their lifetime, but the population as a whole can adapt over time.
On top of this, marine biologists are aware that they probably don’t know everything about (Anchi)tosia starfish yet. All those different colors within T. australis, for example, may indicate that there are different species that need to be described and separated. Time will tell!
Natural habitat
As the scientific denominations of “australis” and “queenslandensis” suggest, biscuit starfish are naturally found in Australia. They also occur in New Zealand, and Anchitosia queenslandensis has been found in the waters around Japan and Papua New Guinea.
In their natural habitat, these starfish are considered shallow-water species, typical sights in rock pools, on pier pilings, and similar intertidal zones. They’re not really found on deeper reefs and in more turbid waters.
Biscuit starfish aquarium
As we mentioned earlier, most starfish are difficult or even impossible to keep in the aquarium (that’s also why we compiled a special list of the easier starfish species). They tend to be difficult to feed and end up starving. The good news is that the biscuit starfish is actually an OK aquarium candidate for the experienced aquarist!
Although these are small creatures, they need a roomy aquarium. This isn’t so they can move around, but because the more space there is, the more edible morsels can develop, helping to prevent starvation.
For this reason, it’s also important to only introduce biscuit starfish into mature set-ups. The older the better, and as long as the water quality is high, it doesn’t matter if the tank is a bit crummy. What looks like grime to us, can be a tasty meal for your sea star.
Aside from tank size and maturity, your biscuit star won’t need much. It’ll appreciate the presence of some crevices to hang out in, but that’s about it. These starfish spend most of their time sitting motionless, though sometimes they zoom across the tank at surprising speeds to get to some edible morsel they’ve detected!
Water quality
One of the reasons we only recommend these starfish for seasoned aquarists is the fact that they’re quite sensitive. Keep water quality, pH, and salinity under control! They may like a crummy tank, but they hate dirty water.
Also be mindful of temperature. This species isn’t for the toasty tropical aquarium; it likes things cooler and will likely start to struggle above 75 °F.
Tip: Although it’s not technically a true starfish, the superficially similar banded serpent star makes a much better choice for small tanks than a biscuit starfish. It’s also much easier to keep alive, so start here if you’ve never kept sea stars before.
Biscuit starfish compatibility
Most aquarium inhabitants will leave starfish alone, although there are some exceptions. The most notable is the harlequin shrimp, whose entire diet consists of sea stars!
Aggressive fish like puffers and triggerfish don’t make good tankmates either, nor do some large wrasses, and large hermits. The green brittle star, which looks like a starfish but isn’t, might also hunt biscuit starfish.
Additionally, you should avoid species that require hot, tropical water temperatures. As we mentioned in the section on water quality, biscuit stars like things a little cooler.
As for whether a biscuit star will pose a threat to its tankmates, the answer is usually no. Unlike most starfish, which hunt clams and snails, this species will leave shell dwellers alone. It’s also not prone to nibbling on corals like some of its cousins, such as the beautiful but fussy chocolate chip starfish.
Are biscuit starfish reef safe or not? We’d say 90% yes. Although some aquarists have seen their biscuit stars sitting on coral, most report this only happens if the coral is already dead or dying, and it’s rare to see it unless the starfish is very hungry. It’s not even always clear whether it’s actually eating the coral!
Tip: Try not to keep more than one starfish per tank unless you’ve got a LOT of space available. It’s already hard to get them enough to eat without two or more stars competing with each other.
Biscuit starfish diet
If you’re interested in keeping a biscuit star, pay attention here please!
Most starfish, including these, are constantly slowly starving in our tanks and likely to kick the bucket in under a year. This being said, a biscuit starfish can be kept alive if you know what you’re doing and stay on top of things.
Researchers have found that biscuit starfish feed on sessile invertebrates. Their favorite meals in the wild include sponges, bryozoans, sea squirts, and tunicates. They don’t seem to eat eat detritus, dead or dying organisms, mollusks, crustaceans, or anything else that other starfish generally like, so supplemental feedings with fish food and such are out.
Now, aquarists have mentioned that their biscuit stars also appear to eat algae and sometimes encrusting corals. We think this is the result of hunger: they’d probably much rather feed on encrusting sponges and the like.
Unfortunately, it’s not really clear what kind of sponges these starfish prefer. The only named species in the studies we read was Aplysilla rosea; the rest of the sponges the biscuit stars were seen eating weren’t named or may not even have names. Aquarists’ experiences suggest they’re not too picky, although folks are generally still kind of groping in the dark when it comes to biscuit starfish diet.
We recommend breeding a steady supply of easy sponges like pineapple sponges (Sycon sp.), blue sponges (Haliclona sp.), and the various random encrusting sponges that tend to pop up on live rock. You can do so in your tank’s sump or a small separate set-up. You can try bryozoans as well, but those are a bit more challenging to grow.
Request: If you see your biscuit starfish eat an identifiable sponge or bryozoan, please let us know! We’ll include the name here so other aquarists can try it.
Breeding biscuit starfish
Unfortunately, we don’t know of anyone who has successfully bred biscuit starfish. It’s hard enough to keep starfish alive, and since their larvae are planktonic, they’re very fragile.
In fact, we can’t find any information on the reproduction of Anchitosia queenslandensis, one of our two biscuit starfish species, at all. It may be a free-spawning species like its cousin Tosia australensis. Alternatively, it may brood its larvae, which is unusual among starfish but seen in Tosia neossia.
Sources & further reading
Keough, M. J., & Butler, A. J. (1979). The role of asteroid predators in the organization of a sessile community on pier pilings. Marine Biology, 51, 167-177.
Mah, C. (2007). Systematics, phylogeny and historical biogeography of the Pentagonaster clade (Asteroidea: Valvatida: Goniasteridae). Invertebrate Systematics, 21(4), 311-339.
Naughton, K. M., & O’Hara, T. D. (2009). A new brooding species of the biscuit star Tosia (Echinodermata: Asteroidea: Goniasteridae), distinguished by molecular, morphological and larval characters. Invertebrate Systematics, 23(4), 348-366.
Tosia australis color comparison photos by Peter Southwood, CC BY-SA 3.0, via Wikimedia Commons.
Cover photo by © Anne Hoggett, CC BY 3.0, via Wikimedia Commons
