New and have a hitchhiker

[Socaldayz]

Hello, I am new to this and have my first take set up. My tank is 30g and has cycled so I added a juvenile clownfish (Bob) 4 days ago. He is doing great (weird but great) and I went in to get a protein skimmer and came out with a small Kenya tree coral.

This morning I noticed a little star on the glass in Bob’s favorite corner. He is just as confused as I am and keeps trying to check it out, but is leaving it alone.
Is it ok for me to keep the little guy? How do I find out what kind he is? Will he likely survive? I wasn’t planning on getting one for at least a year, when I know I’ll get a bigger tank. He’s about 1/4 inch in size.

*I think Bob wants his corner back

tank info:
76 degrees
0 ammonia
0 nitrite
Between 0-5ppm nitrate

 

[Peace River]

It is an asterina starfish. I think you will find that people have mixed opinions, but they have been known to be mildly problematic.

 

[ISpeakForTheSeas]

Welcome to Reef2Reef!

I agree with the above, it's an Asterina starfish (technically Aquilonastra - Asterina is a separate genus within the Asterinidae family). The ones we see in our tanks typically don't get much bigger than the one you've got there (though a few species do). Your tank looks pretty young so I don't know for sure how it will do in your tank at the moment, but these stars generally do survive (and even thrive to extreme levels) in our tanks. So, assuming it handles your tank alright, don't be surprised if you find more, as they are known for reproducing extremely quickly by dropping legs which grow into new starfish.

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" 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, so - personally - I wouldn't be too concerned.

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.

 

[Socaldayz]

Thank you for your help. I did some research on them based of off your recommendations and took him out.

 

[noobreefer2]

Hello, I am new to this and have my first take set up. My tank is 30g and has cycled so I added a juvenile clownfish (Bob) 4 days ago. He is doing great (weird but great) and I went in to get a protein skimmer and came out with a small Kenya tree coral.

This morning I noticed a little star on the glass in Bob’s favorite corner. He is just as confused as I am and keeps trying to check it out, but is leaving it alone.
Is it ok for me to keep the little guy? How do I find out what kind he is? Will he likely survive? I wasn’t planning on getting one for at least a year, when I know I’ll get a bigger tank. He’s about 1/4 inch in size.

*I think Bob wants his corner back

tank info:
76 degrees
0 ammonia
0 nitrite
Between 0-5ppm nitrate

Welcome! Heres are a bunch of people voicing their opinions on these guys...lol

https://www.reef2reef.com/threads/whats-so-bad-about-asterinas.720488/

 

[EeyoreIsMySpiritAnimal]

Hello, I am new to this and have my first take set up. My tank is 30g and has cycled so I added a juvenile clownfish (Bob) 4 days ago. He is doing great (weird but great) and I went in to get a protein skimmer and came out with a small Kenya tree coral.

This morning I noticed a little star on the glass in Bob’s favorite corner. He is just as confused as I am and keeps trying to check it out, but is leaving it alone.
Is it ok for me to keep the little guy? How do I find out what kind he is? Will he likely survive? I wasn’t planning on getting one for at least a year, when I know I’ll get a bigger tank. He’s about 1/4 inch in size.

*I think Bob wants his corner back

tank info:
76 degrees
0 ammonia
0 nitrite
Between 0-5ppm nitrate

Others have already answered your question, but since you're new to the hobby this may be helpful. There is lots of great info in the sticky threads on many forums - check out the others in this one and the ones in the "New to..." forum

What is that!! A R2R guide to common new tank hitchhikers.

One of the greatest things about starting a reef tank is getting your live rock in and admiring all the diversity within it. The rock comes to life different creatures. This is a guide that I, along with a very well known critter identifier @KJ , have put together for the new reefer on what...

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