Five-Armed Friends and Foes.
Updated: Nov 14, 2021
Starfish, or sea stars, are amazing creatures. The way they think, eat, and walk is unique and interesting. If you're thinking about adding a sea star to your home aquarium, there are five common and readily available species that are considered reef safe. This means they won't predate on your fish, corals, or other invertebrates.
The Fromia starfish genus has several different species and is one of my favorites. They are suited for small, well-established aquariums around 50 gallons. They feed on algae films and microorganisms that already exist in the tank, which is why you want a tank at least a year old. One trick with the Fromia is their sensitivity to changes in water chemistry. Make sure they are acclimated with a slow drip over 2.5 to 3.5 hours.
My next two favorites are the serpent and brittle sea stars. These guys are funky dudes with their long reaching arms about eight times the length of their center body. They are hardy and they are excellent scavengers, as they will come out during feeding time and at night to eliminate any extra food. Be careful as they are opportunistic scavengers. This means they are not 100% reef safe as they have been known to feast on the occasional snail, clam, or scallop if they go hungry. Minimum tank size for these guys is also around 50 gallons. Be sure to avoid the green brittle sea star as well, They are avid hunters and not considered reef safe.
The Linckia starfish are vibrant, peaceful and beautiful sea stars. They feed on algae film and are truly reef safe. I only mention them because they are peaceful cohabitants for reef aquariums. However, they are even more sensitive than the Fromia sea stars. I only recommend them for very established aquariums and expert aquarists. The Linckia can reach up to 12 inches and requires a minimum tank size of 150 gallons.
The sand sifting starfish might be an option for you as they are great at consuming detritus in the sand bed. However, like the serpent stars they can be carnivorous and have been known to predate on mollusks, shrimp, and urchins. Use caution with these guys, if they expire in your tank, it will most likely be under the sand bed where they will decay and cause nutrient blooms. They can reach upwards of 12 inches and I recommend at least 100 gallons with 80% open sand bed.
Compared to the non reef safe chocolate chip and green brittle sea stars, the above mentioned starfish are relatively reef safe with the Fromia and Linckia species being at the top of the list.
Whether reef safe or not, what all sea stars have in common is the unique and interesting way they eat. Starfish will protrude their stomach outside their body and partially digest their food externally. Then the stomach and the partially digested slurry is retracted and digested further using their digestive glands. Recently, scientists have discovered a neuropeptide (molecule that talks to neurons) that controls the release and contraction of the stomach (Dean 2013). This is great news for the reefs that have been devastated by the crown-of-thorns starfish (pictured right) as scientists may be able to control the predatory behavior of these destructive species.
But you won't need to resort to all that just to enjoy a friendly starfish in your aquarium. Always remember to do your research and acclimate invertebrates slowly. For more information on sea stars and how to introduce one to your aquarium, scroll down to contact Brian at Boodleshire Aquatics.
Dean C. Semmens, et. al. "Discovery of a novel neurophysin-associated neuropeptide that triggers cardiac stomach contraction and retraction in starfish." Journal of Experimental Biology. 10.1242. 2013,