Crabby Day

Todd · #1 09-30-2008, 06:51 AM

So after several weeks of trying the leaning glass, the baited bottle, the skewer I went for the removal method. I pulled the biggest chuck of LR in the tank out (it was on the bottom, but easy to get to) - making sure that these two guys were on the rock.

Put it into a big rubbermaid and prodded these two guys out. They are both now living in my sump.

I am thinking they are black emerald crabs, can anybody confirm or suggest another species?

purplepolypeater · #2 09-30-2008, 08:14 AM

i cant id but i like the pics

Snaz · #3 09-30-2008, 12:12 PM

Damn those crabs have more cash than I do!

i have crabs · #4 09-30-2008, 12:57 PM

stinky had one in his tank like that guy for a while, defiantly bad thing lived through 2 copper treatments in a qt tank and about 6 months with a 8-10" mantis before it disappeared

Jason McK · #5 09-30-2008, 02:08 PM

I had a purple one. Same pincher shape, that would indecate it eats algae. Mine also eat SPS, LPS, and Zoa

Best to keep it out of the tank

J

blaster · #6 09-30-2008, 05:19 PM

I was waiting for the magic trick.

mike31154 · #7 09-30-2008, 08:16 PM

Looks like a species of Mithrax crab. I literally have a small herd of these dudes in my 75 gal and several of them are a fair size. Prominent scoops on the pincers. From my observations they've mostly been scraping the live rock with their scoops, but I've also seen them go after small meaty scraps. One of them will hang out around my BTA and I've seen it reach in to remove the stuff coming out of the nem when it's expelling waste. It has also tried to take bits of silverside I feed the nem, but the nem is healthy and sticky so it's generally not successful in that regard. Whenever I feed the BTA, I make sure my cleaner shrimp and brittle stars get a small bit of meat first. That way the cleaner shrimp are less likely to come nosing around the BTA. When I first got the nem, it wasn't super healthy or sticky, so the cleaner shrimp stole its food. Now that it's healthy and much larger, the shrimp no longer do this but I still feed them first anyway, just to keep them busy.

From a quick web search I found some info on an 'emerald' mithrax and articles on these report they are generally reef safe as long as you keep them well fed with algae. It won't hurt to offer a few meaty scraps from time to time. Otherwise they may turn to corals. Mine are not emerald, they're quite black as those in your photos. Other than a colony of zoas, I don't have any corals and so far none of these crabs have molested or damaged any polyps. Dunno, so far they haven't been responsible for any deaths that I'm aware of so I'm just not sure I need to yank them out.

untamed · #8 09-30-2008, 08:59 PM

I agree. They look like emerald crabs to me... The flat surface of the main claws suggest that they are likely harmless.

Snaz · #9 10-01-2008, 03:46 AM

Quote:

Originally Posted by untamed

I agree. They look like emerald crabs to me... The flat surface of the main claws suggest that they are likely harmless.

Really no crab is "harmless", all crabs are opportunistic omnivores. Some crabs are less harmful to reefs than others is all.

Todd · #10 10-02-2008, 05:32 AM

Thanks for all of the info. Particularly Mike. Definitely looks to be a mithrax species. I have never seen either of them be aggressive to coral, fish, snails ect. They would grab at meaty scraps (particularly the shrimp that I used to lure it out of its hidy hole), but would mainly graze on algae from my observations.

They have lots of algae in the sump to graze on now.