How about a Zebra Crab (Zebrida adamsii)?

[rizakaniza]

Information on these guys I have found to be very limited. I have heard that crabs can tend to pick at corals and kill fish once they get larger, but from what I understand these only eat urchin spines. Can I pull this off in a 39 Gallon Cadlights Pro? What are your thoughts? Second question is does anyone know where I can get one?

 

[chiclet]

what kind of set up you running? reef etc..... you think it would be wise to put a crab that can get big enough to kill fish and requires a special diet of urchins worth it? If it were me id stay clear.... Maybe the fact you cant find one is a good sign,..

 

[rizakaniza]

I hear what you're saying, really, I do, but I have not come across anyone who has ever had issues with them. I have come across people who got one in their tank by mistake (hitchhiker) and from what I understand it did just fine. This crab ONLY eats urchin spines from what I have gathered, so I don't think it will pose a threat to fish, but I don't know for sure because there is almost nothing written up about this crab. I currently have an empty tank, but I want to do my research before I begin stocking. I have a 39 Gallon Cadlights Pro with a 12 Gallon sump. I have 150w of MH lighting plus 2 x 24W T5HO Actinics. I want to keep SPS, Acans & Rics.

 

[finsurgeon]

I have one now, and have had it for about 6 months. It's completely harmless to all inhabitants except the urchin, never getting over about a half inch in size, and almost never coming off the urchin, except in moving to another urchin. It takes 2 or 3 urchins to share the burden of hosting the crab. I've seen it listed as symbiotic, but I'm not sure the crab does anything for the urchin, so maybe it's more like parasitic. For me, the crab keeps the size of the diadema urchins from getting too big for my tank - I have 2 black long-spines, along with 3 other urchins that seem to be more of a transient host than the preferred long-spines. If you only have one urchin, the crab will wear him down over a few weeks to a couple of months, leading to loss of the urchin, followed by loss of the crab. I see quite a few pictures on-line of adamsii crabs on "radiant urchins" (astropyga radiata), in addition to the black long-spine diademas. I've had a few, sometimes as long a 1.5 to 2 years. I've gotten them in the past from Atlantis Aquariums - http://store.atlantisaquarium.net/zebra-crab-clr-020.html Good Luck.

 

[rizakaniza]

<a href=showthread.php?s=&postid=15567011#post15567011 target=_blank>Originally posted</a> by finsurgeon
I have one now, and have had it for about 6 months. It's completely harmless to all inhabitants except the urchin, never getting over about a half inch in size, and almost never coming off the urchin, except in moving to another urchin. It takes 2 or 3 urchins to share the burden of hosting the crab. I've seen it listed as symbiotic, but I'm not sure the crab does anything for the urchin, so maybe it's more like parasitic. For me, the crab keeps the size of the diadema urchins from getting too big for my tank - I have 2 black long-spines, along with 3 other urchins that seem to be more of a transient host than the preferred long-spines. If you only have one urchin, the crab will wear him down over a few weeks to a couple of months, leading to loss of the urchin, followed by loss of the crab. I see quite a few pictures on-line of adamsii crabs on "radiant urchins" (astropyga radiata), in addition to the black long-spine diademas. I've had a few, sometimes as long a 1.5 to 2 years. I've gotten them in the past from Atlantis Aquariums - http://store.atlantisaquarium.net/zebra-crab-clr-020.html Good Luck.

Surgeon,
Thanks for all the information. It's quite helpful. How big is your tank? Do you think the crab and urchins would do well in a tank my size? Also, between the crabs and the urhins, would they be reef safe? Thanks.

 

[finsurgeon]

You need 2 or 3 urchins for a crab. They would definitely be "reef-safe", but urchins will eat coralline algae, scraping the purple off your rocks. It will grow back (possibly faster because of the processing of the urchin and pooping the spores), so don't freak if you see scraped trails. Urchins also can knock things over, so if you have corals or frags or anything just "set" in place, it will get knocked down. Frag glue or putty solves that. Also, you might start with one diadema and something smaller at first. A diadema without crab will grow fast, and could quickly outgrow your tank, whereas one that is less than 2 - 3 inches may not be big or resilient enough to host yet. If you are worried about tank size and urchins, you can feed urchins by hand, putting nori under their spines or on a clip where they can reach it, or put macroalgae from a fuge into the display. They love any greens they can get much more than anything they have to work harder for. And it seems that 2 crabs on 1 urchin will fight. But neither the crab or the urchins that are recognized as reef safe will harm any other occupant. (The only nonreef-safe I can think of is a pencil urchin.)

 

[rizakaniza]

Thanks again! That was very helpful.