What on earth are these?! (Advise please)

[Johnny191]

Tonight when I visited my fish tank I saw these very strange things that look like a caterpillar, and from the picture you can see they are very small. I saw about 3 of them in the rocks, I got one out and the other 2 are in a rock I know I can take out. But first I want to know what are these?

Secondly there are two small things that looks like starfish, are they Asterina starfish? They are pests? And what should I do about both of these creatures?
I have half live sand and some live rocks in there. I never saw any of these things, but then again I don't often view the tank this late at night.

The tank is just basically cycled and all that, so not an old tank.

Thanks in advance to any help!

 

[((FORDTECH))]

That is a arm to a micro Bristol starfish

 

[exnisstech]

Yep the arm off of a micro brittle star. They like to stay in the rocks and stick their arms out like that to capture food. Good hitchiker. I have a bunch that bother nothing.

 

[ISpeakForTheSeas]

Secondly there are two small things that looks like starfish, are they Asterina starfish? They are pests? And what should I do about both of these creatures?

Yeah, they are "Asterina" starfish (technically Aquilonastra starfish) - some people like them, some people don't; they may or may not eat zoas, and some rare species may or may not eat other corals on occasion too (this one is very rare though):

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.

 

[Johnny191]

That is a arm to a micro Bristol starfish

Hello, thank you for the reply I appreciate it.

Just to clarify the picture where I compare the thing to my finger, I directly captured it off my aquarium glass nearby a leather toadstool. I thought it was some kind of worm because it had a back and forth movement motion. The other two pictures and video where the "arm" is sticking out of the rock was captured as is and I did not try to disturb it because it immediately retracted once I get closer to it.

I can absolutely see the relation to the Bristle Starfish arms, however I am confused as the first one I mentioned I captured off my aquarium glass and it had the movement of a worm like creature.

 

[Johnny191]

Yep the arm off of a micro brittle star. They like to stay in the rocks and stick their arms out like that to capture food. Good hitchiker. I have a bunch that bother nothing.

I captured the thing that I compared the size to my finger in that picture directly of my aquarium glass wall. I am really not sure if it could be a free-moving arm of a bristle starfish or whether it is a worm like creature. The video and the other pictures of the worm like thing / bristle arm retract as soon as I get near it.

I am so confused, a local fish store representative told me (Direct translation here in China into English) "It is a cylinder caterpillar." (Very difficult to know the exact name and whether or not it is a danger for my tank.)
Thanks a million for the reply

 

[Johnny191]

Yeah, they are "Asterina" starfish (technically Aquilonastra starfish) - some people like them, some people don't; they may or may not eat zoas, and some rare species may or may not eat other corals on occasion too (this one is very rare though):

Thank you very much for the detailed information and I appreciate it very much!

I tried to count how many of these starfish I can see and I got to about 4 of them, also I have only one frag with zoas and no big population steady yet. Would you remove these starfish personally or let them be?

Again, thank you for the really valuable info!

 

[exnisstech]

I captured the thing that I compared the size to my finger in that picture directly of my aquarium glass wall. I am really not sure if it could be a free-moving arm of a bristle starfish or whether it is a worm like creature. The video and the other pictures of the worm like thing / bristle arm retract as soon as I get near it.

I am so confused, a local fish store representative told me (Direct translation here in China into English) "It is a cylinder caterpillar." (Very difficult to know the exact name and whether or not it is a danger for my tank.)
Thanks a million for the reply

I very well could be mistaken but I have hundreds of them through out my tanks and they look exactly like those shown. I'm sure others will respond so you can get some other oppinions.
Happy Reefing

 

[Mhamilton0911]

Tonight when I visited my fish tank I saw these very strange things that look like a caterpillar, and from the picture you can see they are very small. I saw about 3 of them in the rocks, I got one out and the other 2 are in a rock I know I can take out. But first I want to know what are these?

Secondly there are two small things that looks like starfish, are they Asterina starfish? They are pests? And what should I do about both of these creatures?
I have half live sand and some live rocks in there. I never saw any of these things, but then again I don't often view the tank this late at night.

The tank is just basically cycled and all that, so not an old tank.

Thanks in advance to any help!

I'm going to come in with zero official names, but yeah.

First picture definitely looks like a micro brittle starfish arm, I have hundreds of those from my live rock. However, what you captured off the glass definitely looks like a worm, just not a good picture to zoom, but i get these all the time as well, they have a definite head, which looks like some type of Eunice worm, there are so many types. Some bad guys, some harmless. I try to remove all I see but I can only get mine off the glass, it's no chance in rocks, they are wicked fast.

And yes, asterina Star. I have many too, some report they eat zoas, or just ugly looking everywhere but i toss mine into the sumps and they work hard in there.

 

[Dan_P]

Tonight when I visited my fish tank I saw these very strange things that look like a caterpillar, and from the picture you can see they are very small. I saw about 3 of them in the rocks, I got one out and the other 2 are in a rock I know I can take out. But first I want to know what are these?

Secondly there are two small things that looks like starfish, are they Asterina starfish? They are pests? And what should I do about both of these creatures?
I have half live sand and some live rocks in there. I never saw any of these things, but then again I don't often view the tank this late at night.

The tank is just basically cycled and all that, so not an old tank.

Thanks in advance to any help!

If it moves, it is a bristle worm.

 

[Johnny191]

I'm going to come in with zero official names, but yeah.

First picture definitely looks like a micro brittle starfish arm, I have hundreds of those from my live rock. However, what you captured off the glass definitely looks like a worm, just not a good picture to zoom, but i get these all the time as well, they have a definite head, which looks like some type of Eunice worm, there are so many types. Some bad guys, some harmless. I try to remove all I see but I can only get mine off the glass, it's no chance in rocks, they are wicked fast.

And yes, asterina Star. I have many too, some report they eat zoas, or just ugly looking everywhere but i toss mine into the sumps and they work hard in there.

Thank you, good advice on putting them into the sump for working down there. I feel way too bad to get rid of them in any other way unless someone wanted them haha. Since my tank is fairly new still I have a lot of fresh algae and these starfish seem to be eating it for now.

I will try keep a close eye on the thing coming out of the rock in the meanwhile.

Are there any fish that likes to eat maybe some of these pets? I have a peppermint shrimp and I worry another shrimp will fight with him if I got a harlequin or something.