Small Starfish Species?

hey just letting you know i used to work at a pet store and we had a ton of these astrenas in our 75 gal reef display and i also had them in 45 reef and have never had a problem. but if your not so into the idea of possibly being over run by them or haveing them possibly eat all your corals there is a species of starfish that stays about three inch arm to arm. the pet store i used to work for accidently got some in on some lr and decided to leave them and see what they would do they have been in there for about 2 years now and have not caused a problem and have procreated as well i had gotten one for my pico about 3 months ago and now have two so they appear to be asexual and also they look like tiny brittle stars and are very pretty so you might want to check them out if you can find them anywhere