id please

reeferchickdc · #1 05/06/2007, 05:46 PM

I added a couple of corals to my 10g nano a few months ago, they must have come with them? They are smaller than my finger nail. I've found four of these in my tank this week. can anyone id these?

ATJ · #2 05/06/2007, 06:18 PM

They are sea stars, probably of the genus Patiriella. Looks like they have been reproducing asexually and haven't quite grown all their arms.

reeferchickdc · #3 05/07/2007, 09:37 PM

cool. thanks. are they friend or foe?

ATJ · #4 05/07/2007, 10:03 PM

Could be either. Some species feed on corals. Most are carnivores. Just keep a close watch on them for now.

coralnut99 · #5 05/08/2007, 11:18 AM

Asterina stars.
Can be a PITA, but largely benign and easy to control. When they don't have enough film algae available, they munch on your coralline algae. They can have some really weird leg configurations. Almost never a perfect starfish shape.

reeferchickdc · #6 05/09/2007, 09:41 PM

If they don't eat my corals then... sweet! They look pretty cool in my nano.

ATJ · #7 05/10/2007, 02:44 AM

I still recommend you keep a close eye on them - especially at night.

erendon · #8 05/10/2007, 06:05 AM

Be careful, they multiply fast. I had them in my tank and it was not a good thing. I was taking about 10 out at night. Now every time that I see one I take it out. They started to eat some sps's and mover to some mushrooms.

coralnut99 · #9 05/10/2007, 10:48 AM

I dunno about them being coral munchers. They are essentialy opportunistic herbivores. I've had my share of explosions of these guys over the years. I can't say they've actually eaten a single coral. Believe me that spans a lot of years, and a lot of corals. Do they multiply fast? They certainly can, and if they have enough food, they seem to multiply in harmony with the food supply. Should you keep them in check? I think so. I think their worst character trait is their appetite for muching on coralline algae when there isn't enough film algae for them. The coralline on your glass will start to look like small scattered specks instead of large solid patches.

ATJ · #10 05/10/2007, 04:10 PM

With some obvious exceptions, identification of invertebrates from photographs alone is generally difficult. The accuracy of the identification will vary between taxonomic groups but with sea stars most you will only be able to identify to family or genus at very best. The sea stars here are almost certainly in the family Asterinidae and could very well be Asterina, but as to the species, that could only be determined by microscopical investigation. Without knowing the species and the feeding behaviour of all possible species, it is difficult to be definitive about what they will or won't eat.

I have seen photographs of sea stars that "look" like these feeding on corals. Are they the same species? It is not possible to tell. Will these ones eat corals? It is not possible to tell.

At this point, I believe all you can say positively is that they are sea stars and they are opportunistic. As with any hitchhiker I find in my tanks, I say give them the benefit of the doubt (innocent until proven guilty), but watch them closely and be prepared to act quickly.