ID this rock creature please

[Taliciaakers]

I have recently started a tank and my live rock is alive. Lol no truly it has cracks that open like a lid. Does anyone know what these are. I have looked for hours at bivalves etc but can't ID it. It only opens a few millimeters and you can see that is is soft inside but it doesn't have two shells. It literally looks like a rock opening. If I did the picture right it is the crack below my clownfish. If I didn't please let me know what to do. Thanks

 

[Taliciaakers]

Oops apparently it posted the pic sideways lol sorry

 

[Taliciaakers]

Here is another pic but you still have to turn it sideways. You can see his insides, it is black and white striped but almost barely open. Seems to have a spiky edge on the "inside" part of it. Also I'm not talking about the sea urchin underneath him. It's the crack above the urchin I can't id.

 

[bobpiker]

Looks like a spider someone else also posted a photo of in their tank. Until I saw that photo, I wasn't aware there were marine spiders to be found in a marine tank.

 

[Betta132]

I'd say it's a coraline-covered oyster. Some oyster species attach their bottom shell to the rock, making them look like lumps and also hiding the fact that they do indeed have two shells.
He's a filter feeder, so I'm not sure how well he'll do. Depends on your tank size.
Not entirely sure how you're seeing a spider, bobpiker... Unless you're looking at the urchin? There are sea spiders (not real spiders, fortunately), but this critter doesn't appear to be one.

 

[pagojoe]

Yeah, it's going to be an oyster or "Rock Scallop" (which isn't really a scallop). It's harmless.


Don

 

[Taliciaakers]

Thanks. I appreciate the help. I have a 10 gallon that's been up for 5 weeks. Live rock has been in there the whole time and everything on it is still alive(knock on wood) but I just introduced the clownfish. And yes I know they will eventually need a bigger tank. Feeding flakes and pellets but only my cuc seems to be really eating. Hope the clownfish will start eating better. Have had them 3 days.

 

[Taliciaakers]

We'll almost everything's still alive. My brittle star ate all my feather duster worms.

 

[bobpiker]

Isn't that a "spider" at 3 o'clock, far right? Sure looks like one.

 

[Betta132]

I'm seeing a small sea urchin (pencil urchin, I think) and a blurry aiptasia anemone. No spiders. I suppose they do both look a bit like spiders, but neither has jointed legs and both are rather distinctive after you've seen a few.

 

[Taliciaakers]

I see what you are talking about bob. It's actually some kind of red algae coral stuff. It's hard and branchy but thin and small. It's like hair but stiff. Their is a sea urchin and an aiptasia in the pic. Haven't found any spiders yet but I find different things frequently. It makes keeping this tank ten times better. I love how much life is in the reef and how it's so varied. Got some shells for free from lfs for my hermit crabs and two of them had bristle worms in them. I just think the surprises are so cool. Sorry I'm done now

 

[bobpiker]

Thanks for clearing that up. After someone else posted a photo of a real spider in their tank it has me looking for one, too...the dreaded salt spider.

 

[Calappidae]

Sea spiders are surprisingly harmless and best ignored.. kinda like nudibranch each has it's own diet and will starve if not present. Worst case it's diet is a coral.. but by that point in a tank's maturity any coral eating species would have starved since no coral should be in there that soon anyway.

If it is a good sea spider it may even be benefical eating hydroids and other nasty unwanted things!

But of course.. there is no way to tell what eats what and even being able to supply the food if one saw the spider eating would be nearly impossible to keep up with.

 

[Lauracooks]

i'd do somthing about that aiptasia