Is this a tank safe crab? Toxic Zosimus aeneus

[Om_Seeker]

Hi folks,

After about a month and a half of cycling, I've discovered a hitchhiker crab that I never noticed before. It's a small one (carapace less than one inch) and only comes out when it's pitch dark -- which is probably why I never noticed him before.

So after some hide-and-seek episodes, I believe I've identified the little guy as a Zosimus aenus similar photo from Australian Museum.

My crab doesn't look exactly like this one but the description of the bumpy shell makes me think he is a Zosimus aeneus.

My first question is -- in one of my books, they briefly mention that these types of crabs are not reef friendly but okay for a FO tank. What do you guys think? I am not at the reef tank stage yet but hope to be some time soon. Should I get rid of him?

My second question is -- Should I get rid of the crab because he is toxic? I didn't realize that Zosimus aeneus crabs are super toxic! Check out this article on poisining death after eating this crab article article . Supposedly a single crab has enough poison to kill thousands of people! Can you believe that the CIA used to use the saxitoxin poison that is found in the crab (and certain algae blooms) for its suicide pills? another article.

I suppose if I don't eat him (which I don't plan on doing), he's not a poisonous threat to me. But is the crab's toxicity a concern for the tank environment?

Thanks for your comments.

[Craig Manoukian]

Where is your rock from and how do you think you got something from Australia/Papau New Guinea in your tank?

[Om_Seeker]

Hi Craig,

Thanks for asking. My LFS said the live rock is from Bali, Indonesia.

I finally got some pictures of the crab who spends most of his time hidden. Actually, my wife took the pictures after a lengthy stakeout!

Perhaps it's a case of mistake identity but the crab sure looks like a type of zoisimus aeneus to me, particularly with the bumpy carapace. Maybe with your expert eyes, you can tell me otherwise.

(Okay, now I have to figure out how to post a photo to a reply. Seems like I can only post a photo to a new thread. Hmmm. I guess what I will do is post the photo under my profile. Please check out the pictures there.)

Thanks!
Greg

[Craig Manoukian]

OK,

Bali Indonesia is part of the region that that crab is indigenous. Very well could be one in the same. Shouldn't pose any toxic risk, but crabs with pincers are opportunistic feeders and will generally pose a threat to other crustaceans or small sleeping fish.

[Om_Seeker]

Thanks, Craig.

I hear you about the pincers and threat to inverts and small fish (damsels!), but what about soft corals and other corals? One of my reference books says they are not reef safe.

Greg

[Craig Manoukian]

as I'm not familiar with that species, it is very possible that it will eat corals.