Little starfish

[Kathy Floyd]

So this little one showed up today. Can I keep it?

 

[ISpeakForTheSeas]

Asterina starfish (technically Aquilonastra, but known in the hobby as Asterina). Personally, I like them, but they reproduce quickly (very quickly), and some people believe they eat corals (see my quotes below).

With regards to whether or not they eat corals, it might be a species specific thing, it might be a you have way too many starfish so they're out of other food options thing, or it might be they're eating the slime coat/mucus on the coral rather than the coral itself (see below).

It's an Aquilonastra spp. starfish and is a great scavenger. I see them with anywhere from 4 to 12 legs. The whole discusion around them seems to me excellent examples of misidentification, mistaken behaviour and assumed causality based just on heresay without looking at the research. Asterina spp starfish are preditary but only reproduce sexually and are shortlived so while it's possible some might get into a tank even if it did happen it's not going to be around long. Aquilonastra are one of the uncommon species that reproduce fissiparous or by splitting so are easy to identify by the different sized legs regrown after splitting. They perform an important function not only feeding off algae films but also feeding off microbial films including those on corals (at least ones that don't sting). FYI the mucus coating on corals ages and corals have to periodicely shed it to renew it and maintian healthy microbial processes (Ref 1, Ref 2). If Aquilonastra are feeding on zoas or softies I'll argue they are either benign or even beneficial as they may be reducing the unhealthy older mucus which can be full of unhealthy microbes which the animal is trying to get rid of and are far more likely to be the actual problem.

Here's an example, this Toadstool is doing one of it's periodic sheddings. The Aquilonastra have been in this system for years but only climb onto the Toadstool when it's shedding. In the first picture you can see the old mucus film, Aquilonastra starfish and areas they have cleaned off. The second picture shows the Toadstool a week later.

 

[CoralB]

Yes you can keep it if you don’t mind the company he’ll have in the future . They multiply and if you don’t mind that your good to go . But at some point you will have to buy a harlequin shrimp to clean or eat them out for you later. I’ve never experienced them going after my coral but some say this is true .

 

[Jedi1199]

I have never seen them go after my corals either. Read that it can happen, but not seen it in my own tank.

Found one of those in my tank a few months back, now every night I have 50-75 of them all over the glass. They seem to venture out after dark and retreat when the lights come on. I very seldom find one on the glass during the day.

 

[jeffchapok]

Sure, you can keep him. And 1000 of his closest friends.

I leave them alone. They don't seem to bother anything.

 

[Nemo&Friends]

They mainly are filter feeder, but as they clone themselves they reproduce fast. If you have too many, get an harlequin shrimp, they are beautiful. However they eat only sea stars, so when your supply is over, you have to give it back to the store or pass it on to another tank. I just did that, I called it renting an harlequin shrimp. I had over 300 stars, and it took about 8 month for the shrimp to go thru the supplies. He/she ate about 3 a day.

 

[Alexraptor]

Asterina's "can" definitely go after corals, in particular I've had them go after my zoas.

However!!!

IME this is highly individualistic behavior. In general they are harmless and leave corals alone, and simply removing the troublesome individuals from the tank is usually enough.

 

[Timfish]

Yes, you can keep it. It's easy to wipe them off the glass and remove them with your hand when they get to be to many.