Who ate my dusters?

[Mihai]

I had some nice white feather dusters, fairly large (maybe 3/4" diameter) that liked my tank: they went from 2-3 to 20 in about 2-3 months. Then I added some clean-up crew: 4 blue legged hermit crabs, 4 emerald crabs, one brittle star (the one that's all spiky). Somebody ate all (or almost all) dusters in the last few days. It doesn't happen during the day, it must be at night.

Any ideas who? Anything I can do to help the last 2-3?

Thanks,
Mihai

 

[Len]

My bet is on the mitrax crabs, with hermits a close second. My feather dusters died out on their own in a short period of time.

 

[danmhippo]

What color is the brittle star? How large (diameter) is the emerald crab?

 

[Mihai]

The star is an Ophothrix fragilis (see link below). The crabs are about 1" diameter.

http://www.saltwaterfish.com/site_11_03 ... arent_id=4

All dusters gone now. I'll try to get others when I'll install the refugium.

Thanks,
Mihai

 

[Mihai]

OK,

More data coming in: in addition to the dusters being eaten, I also have the hydroids disappearing at the same time as the dusters.
(that's probably a good thing).

Also the same thing is eating my sycoid (or so) sponges - the little white ones with opening on top. I had one on the glass about 3" above the surface of the sand and it got eaten as well.

This starts to point toward the brittle star, as I don't think that the crabs can climb on the glass.

And none of my soft corals (zoanthids, polyps, gsp, devil's hand, leather, xenia) got eaten (yet).

Any ideas now considering the new data?

M.

 

[Anonymous]

The only things I know that regularly exit the water by walking up the glass are my snails.

I would say that the one out of water died naturally and just looks eaten, and keep pointing my finger at the emerald crab.

 

[Mihai]

OK, You're right: I was confusing: the sponge ws 3" above the surface of the sand, not above the surface of the water (how could it get there?!).

So the sponge (and everything else) was eaten under water. Again, the only things added were the brittle star, emeral crabs and astrea snails.

It could be that they just died off, but I don't think so: the sponges keep multiplying despite being eaten (they just do that in well hidden places now).

M.

 

[paats]

The star you have is a predator.I have two that I have to keep in a tank alone because they will clean out small fish and shrimp from a tank.I speak from experience.I `m not sure they eat all you`ve listed but I`d take a close look at that guy first off.

 

[Mihai]

Really? That seems unlikely: Robert Fenner in his "Reef Invertebrates" said that the entire brittle star family is reef safe... This is not? It might not be a brittle star?

Do you have a reference to that? If this is the case, it sucks!

Thanks,
Mihai

 

[Mihai]

OMG, you're right: it's not the common brittle star (Ophiothrix fragilis). It's a Black Brittlestar ( Ophiocomina nigra) or anyway, something in this genus. This sucks. I'll have to see what to do with it.

M.

 

[wade1]

I'm guessing that alot of your lack of organisms is just the age of the tank.... if you feed more phytoplankton and small particulate food, you will get more growth from them.

Wade

 

[Mihai]

Wade,

This doesn't seem to be the case: before I introduced these new cleaning crew things (dusters, sponges, hydroids) were multiplying a lot. I mean, I got from 2-3 sponges to 20 in 2 months; same for the dusters: from 2 to 20-25. And they all disappeared in 2-3 days. Same for the hydroids. It's too much, too suddently to be a coincidence.

Besides, the sponges and hydroids that are well hidden survived (none of the dusters though :-( ).

I don't run any mechanical filters and I can see lots of particles in the tank (maybe 100 in each cubic inch). My small dusters (1/4" red/orange/white) are still OK and multiplying, it's just the big ones (1", white) that got eaten.

The idea is that if they multiplied that much, they must have had some food... and again, I can also be wrong (it's known to happen ).

Thanks,
Mihai

 

[wade1]

Ah. Well, it certainly sounds like something/everything is preying on them. You can give them a leg-up by feeding more phyto though.

Sounds like the tank is coming along at least!

Wade

 

[Mihai]

It does come along nicely.
Thanks,
Mihai