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.