Starfish was riding a snail

Meat_Juices · May 20, 2024

It’s a zoomed in pic he’s only about the size of my pinky nail I just want to know if he’s safe to keep

ISpeakForTheSeas · May 20, 2024

Meat_Juices said:
It’s a zoomed in pic he’s only about the size of my pinky nail I just want to know if he’s safe to keep

Aquilonastra starfish (known in the hobby as Asterina starfish) - reef-safe with caution is probably the best description at this point. There are a lot of species in the genus; some seem to be safe/beneficial, others not so much.

That said, the problem species seem to pretty much only eat zoanthids (with very, very limited exceptions), so if you don't have those they should be safe to keep.

A bit of an info dump on them to help you decide:

ISpeakForTheSeas said:
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.

TeamAquaSD · May 22, 2024

Meat_Juices said:
It’s a zoomed in pic he’s only about the size of my pinky nail I just want to know if he’s safe to keep

Asterina star. Some kinds can eat corals but I am sure there are a ton of different variants.
They can reproduce quite quickly. Harlequin starfish are often purchased to get rid of them however you will need to either feed them more starfish or rehome it after the asterina issue is resolved