Asterina Starfish (AKA MiniStar Fish)
Description
Asterina starfish, or more commonly known as mini starfish are generally a few millimeters to just over a centimeter in size with a large body, irregular arm length, and an irregular number of arms. Some do not appear to have any legs at all but just resemble a small greyish blob surrounded by tube feet.
Where to find them in your tank
They tend to hide among corals and in the crevices of the live rock and can sometimes be seen clinging to your tank glass. Basically they can be found just about anywhere in your tank.
What They Eat
Aterina Stars are opportunistic feeders. Feeding mainly on coralline algae (some say even corals; specifically acropora, xenia, green star polyps, zoanthids, and several types of soft leather corals.)
Reproduction
Asterina sp. can reproduce asexually by splitting in two across the center.These starfish divide across the main body with two or three legs of varying lengths and multiply rapidly.
What's The Problem?
So you bought a coral and it has a mini star on it. What's the big deal? Well today you see one, then tomorrow five, and so on. Asterina Star Fish reproduce quickly and can quickly overrun your tank. Like Aiptasia the population of these "cute" stars can explode and have major ramifications to your tank.
There are many debates to whether they actually eat corals. We believe that the problem is just sheer numbers that they can reproduce to. That and the more space they take on a coral; the less lighting the coral would recieve. This being said if they block out the lighting they can cause major damage and possibly death to your corals (this is if you allow them to get to plague proportions)
Solutions
If you notice that your asterina stars are getting a little out of control physical removal is definitley the quickest solution. Although tedious and time consuming (if you have a ton) you can remove them easily from your tank.
Harlequin Shrimp - If you are looking for a nice addition to your tank that will also take care of these little stars. Check out the harlequin shrimp. Harlequin shrimp (Hymenocera elegans) belong to the family Gnathophyllidae and are small, white shrimp with camouflage markings that vary from brown through grey to a purple blue. They are unusual shaped in that they are small and squat and have large adapted front claws that resemble paddles. Harlequins are obligate sea star eaters, which means they will ONLY eat starfish, and nothing else.
The problem with these shrimp is that once you run out of stars (note they will eat ANY stars they can find in your tank) they will not have a food source. You will need to supplement them with extra starfish. Also, like all additions to your tank please look into the care and tank compatibility before introducing these to your tank.
Bumblebee shrimp aka Striped Harlequin (Gnathophyllum americanum) While these shrimp are not as colorful as their cousins the Harlequins, they are not obligate feeders on the tube feet of echinoderms and thus will not require supplemental feedings of sea stars, or legs of sea stars, once they have consumed all of the Asterina sp.
Sources
http://www.reefkeeping.com/joomla/index.php/current-issue/article/45-reefkeeping-101
