Baby arrow crab?

[billygalaxy]

Spotted this guy in my tank. Is this a baby arrow crab or something else? Pretty tiny and hard to photograph...

 

[sfin52]

Spotted this guy in my tank. Is this a baby arrow crab or something else? Pretty tiny and hard to photograph...

I don't think so. The legs of an arrow crab are thin.

Possible sea spider

 

[DaJMasta]

Baby decorator crab.

 

[billygalaxy]

Baby decorator crab.

Thanks for the ID!
Do they get much bigger? Are they reef safe?

 

[Reefkeepers Archive]

I don't think so. The legs of an arrow crab are thin.

Possible sea spider

Definitely not. That's a crab of some sort

 

[DaJMasta]

Thanks for the ID!
Do they get much bigger? Are they reef safe?

There are different kinds, and sort of yes and no. They get their name from the behavior of cutting off little bits of things and sticking them to their shell to act as camouflage. This can include corals, so while they don't eat it, they can cut off a couple of zoas (for example) and bring them somewhere else. Some people consider them not reef safe, some people (myself included) think they're generally alright.

Some species can get to be maybe 25-35mm long (carapace), and some can get larger, I don't have the ID skills to tell you which you've got. Bigger ones would be more problematic as they could opportunistically eat small organisms, but if it starts getting bigger, it probably won't be too difficult to catch when you notice it.

 

[Paul B]

Looks like a species of rock or in some cases a decorator crab. They are very common in the sea here in New York and here anyway get about as large as a baseball. But your tropical one probably will not get that large. I realy don't know.