Tube anemones and crab leg?

[Bret Brinkmann]

Found this claw/crab leg looking thing in my tank yesterday. I do have snapping shrimp but they are a lot smaller than this. No signs of anything predatory going on though.

Here are what looks like some type of small tube anemones that showed up. Haven't added anything to the tank in over two years. Any idea what kind? Color doesn't show up well but they are bright iridescent green.

 

[ThunderGoose]

Yep. That looks like a crab leg alright. Possibly a molt from a as-yet-undiscovered hitchhiker. If there's no predation I wouldn't worry.

The bright green things look suspiciously like green colonial hydroids. I don't have any experience with them, though, so wait until someone like @Maritimer or @kt chimes in before panicking.

 

[reef lover]

Panic...hydroids...

 

[Maritimer]

I would say hydroids as well - they've got a sting that's hazardous to corals, and spread quickly.

The crab leg looks like it's been there a while - have you added any substrate or anything lately (Months, even?)

~Bruce

 

[Bret Brinkmann]

More like years. But my snapping shrimp recently moved under a different rock and I think the claw was cleaned out from under it.

I have read up on the green colonial hydroids and I believe that is what they are. They have gone away on their own for many people. I only have one coral in my tank now so I will leave them. I have also read one member had them against some zoas without incident. So maybe they don't sting everything?

 

[Cnidoblast]

Regarding the claw Just to be safe I would remove the entire area I marked in black from the tank

 

[Bret Brinkmann]

I was planning on using it as a warning to other crab hitchhikers ;Dead, but it would be pretty cool to look at it under the scope. I will take it out and post pics for the fun of it.