What are these?

[Shark_j66]

 

[Czynot]

Asterina star fish. Harmless but can get out of hand.

 

[homegrowncichlid]

just as good as a snail for cleaning the glass., well a tiny snail that is. heh

 

[Shark_j66]

Thank you! There starting to show up all over in my tank lol

 

[Jerseyreefer]

Thank you! There starting to show up all over in my tank lol

White ones are harmless. Black ones can be a pain. But I’ve really only seen them bother sick corals. You will literally get thousands of them.

 

[shanewood2022]

White ones are harmless. Black ones can be a pain. But I’ve really only seen them bother sick corals. You will literally get thousands of them.

You say may be right but according to my power of thoughts both are harmful.

 

[ScionFRSguy]

I would try to get them out of there whenever you see them. I think that the reef tanks should not have any of them at all.

 

[Timfish]

It's an Aquilonastra spp. starfish, beneficial. Often misidentfied as an Asterina spp. Aquilonastra species primary method of reproduction by splitting (fissiparous) is unique. ( Astrina are rather shortlived and only reproduce sexually so are unlikely to maintain viable populations.) Aquilonastra feed on biofilms and algae. In the case of aging biofilms or biofilms that have shifted to pathogen dominate they may provide as essential service to corals helping corals renew their biofilms.

 

[Zuska]

These like to eat my zoas! They would always be all over my zoa colonies and I had to get a harlequin shrimp to get them fully out my system

 

[Timfish]

I've also seen them on my zoas. The mucus film on corals ages and can start to favor pathogenic microbes and has to be shed. (And FWIW we can't use color as an indicator of health, in fact, bight colors can indicate a unhealthy coral.) In all likelyhood the Aquilonastra were doing your zoas a favor by removing aged biofilms.