Little Sea Stars?

[His Coral Highness]

I had two of these guys hitchhike in off a tube worm shell. I think it is a sea star that is maybe missing a leg or two? So far they seem to not be causing any problems but I'm not sure if they will down the road...

 

[TnFishwater98]

Can’t see video..Can you post a pic…? It’s probably a Asterina

 

[Cthulukelele]

Can’t see video..Can you post a pic…? It’s probably a Asterina

It is, in fact, an asterina. That tells you how ubiquitous they are in the hobby lol

 

[His Coral Highness]

It is, in fact, an asterina. That tells you how ubiquitous they are in the hobby lol

Thank you! Anything to worry about?

 

[Cthulukelele]

Thank you! Anything to worry about?

You'll get conflicting reports. They grow in pop very fast but are usually benign. Some reports of coral munching here and there, but mostly people who dislike them dislike that they grow over EVERYTHING

 

[EricR]

By most accounts, they're harmless, although some say that some species may go after corals.

Biggest issue is that they can reproduce like crazy and end up everywhere.

One way they can reproduce is by dropping off legs which is why it's common to see them in odd shapes, missing legs.

 

[thepotoo]

The real problem with them is that guests look at my tank full of thousands of dollars of coral and fish and all they say is "oh look at the cute little starfish!"

 

[ISpeakForTheSeas]

Personally, I like them, but they do tend to reproduce very quickly.

I've heard some species eat corals and others don't - I've seen convincing evidence for one species (a very darkly colored one), and one piece of somewhat convincing evidence for one different species, but the vast majority of these guys seem to be at least mostly safe.

With regards to whether or not the average "Asterina" (technically Aquilonastra - Asterina is a separate genus within the Asterinidae family) 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, it might be they're eating the slime coat/mucus on the coral rather than the coral itself (see below), or they might just opportunistically eat unhealthy corals. Based on how starfish eat, it seems plausible to me that it may also be coincidental (i.e. the star goes to eat something off the coral and the coral just happens to be one that is able to be negatively effected by the star's everted stomach). Regardless, Zoas are just about the only coral I've heard about regular "Asterina" stars potentially going after with any sort of frequency.

A quote I like to refer to for this:

Timfish said:
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.

 

[TnFishwater98]

I’ve got them in all my tanks.

 

[His Coral Highness]

Personally, I like them, but they do tend to reproduce very quickly.

I've heard some species eat corals and others don't - I've seen convincing evidence for one species (a very darkly colored one), and one piece of somewhat convincing evidence for one different species, but the vast majority of these guys seem to be at least mostly safe.

With regards to whether or not the average "Asterina" (technically Aquilonastra - Asterina is a separate genus within the Asterinidae family) 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, it might be they're eating the slime coat/mucus on the coral rather than the coral itself (see below), or they might just opportunistically eat unhealthy corals. Based on how starfish eat, it seems plausible to me that it may also be coincidental (i.e. the star goes to eat something off the coral and the coral just happens to be one that is able to be negatively effected by the star's everted stomach). Regardless, Zoas are just about the only coral I've heard about regular "Asterina" stars potentially going after with any sort of frequency.

A quote I like to refer to for this:

Thank you so much for the detailed response!