Asterina starfish, or more commonly known as Fiji starfish are generally dime sized or smaller with a large body, irregular arm length, and an irregular number of arms. They tend to hide among corals and in the crevices of the live rock during the day and can sometimes be seen clinging to the corners of the tank. This type of starfish has been shown to eat coralline algae and some corals; specifically acropora, xenia, green star polyps, zoanthids, and several types of soft leather corals. These starfish divide across the main body with two or three legs of varying lengths and multiply rapidly. Remove these starfish ONLY if they start to bother your corals. (nanoreef)
This picture was taken with a bright pinpoint backlight flash that shows the circulatory system of the asterina starfish. At one point, I had so a significant number of asterina starfish in my tank. They were not bothering my corals, but I was still concerned about the population of them. I got a Harlequin Shrimp that quickly took care of this problem and kept the numbers under control.
Bob I've found this info very very helpful. I've got a very nice one (so far) and have chosen to leave him be (for now) I've yet to see him on any of my corals. Mostly on the LR, glass and some equipment. I will be keeping an eye on him for sure Thanks.
Thanks for the cool pic BeakerBob. I'd like to add one of a different species. Most of the Asterina I have are irregular and small. This is the second one I've found of these. The photo below is out of water, and upside down showing the mouth. I've had them both with 5 and 6 arms, symmetrical unlike most I see, and grows to 30mm-35mm. I found this one inside my Birds of Paradise, it may also explain my zoas vanishing overnight.
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