Mistery seastar

[João A M Gomes]

Tiny seastars like the ones pictured seem to be reproducing fast in my nano-reef. They do not attain 1/2" in diameter and appear blue under my lighting.
They look superficially like the european Asterina, but I have no idea about their id and at first I thought they were a nice addition to the aquarium. However I was advised that despite their diminutive size, they could be predatory upon soft and stony corals and, most amazingly, that they could destroy coralline algae (an herbivorous seastar???).
Has anyone had similar experiences?
Any comment would be greatly appeciated. Thanks

 

[Bongo Shrimp]

They can become a plague if you let the population get out of control. Get a harlequin shrimp to take care of them. Some eat coral some do not but it's better not to risk it.