Is This Starfish Reef Safe?

[W0terMoist]

Should I pitch every one of these that I find? Or should I keep them? Sand colored body, black and red specks; see attached photo.

 

[ISpeakForTheSeas]

Edit: for clarification, you have an Aquilonastra star there (known in the hobby as Asterina - see below). Personally, I like them, but not everyone would say to keep them.

Some people say yes, others say no - most people seem to say yes, but probably not with zoas:

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 (cases of them potentially going for other corals happen about as often as reef safe fish like tangs or clowns going for corals).

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.

 

[death-by-reef]

probably asterina star, some ppl hate them and think they're ugly i dont mind them personally, think they're kinda cool. harlequins may eat them, idk

 

[W0terMoist]

I will probably just play it safe and pick them out if I ever see any. This one, I saw on the base of my torch (could be a coincidence) so I feel that being cautious is my best bet. I do find them cool lookin though. I love all soft algae, coralline algae, stars, bristle worms, and other 'pests'. Feels like a true-er representation of an actual reef/ocean with all them in the tank.

 

[death-by-reef]

I try to stand along those lines to. I generally try to keep as much of a diverse environment as possible. I feel like the answer to a lot of the problems that come up could be fixed w/ greater diversity. Also seeing all the little creatures doing their job is just plain cool