Is this an emerald mithrax crab?

Spudsly · 02/01/2017, 09:54 AM

I just ordered an emerald mithrax crab from liveaquaria (along with some other things). I attached a picture below. It is somewhere between brown and red. Should I add this to my tank?

nitr8 · 02/01/2017, 09:56 AM

I added 5 green emeralds to my SPS tank and 4 of the 5 I had to remove because after they rid the tank of bubble algae they started sucking on SPS polyps for the slime.

kevin21 · 02/01/2017, 09:59 AM

That does not look like an emerald to me due to the coloration. However, the body structure and claws are extremely similar. The very basic and broad rule of thumb is if their are any black on the claws, its normally smart to remove from the tank. This crab doesn't seem to have any black. It is probably safe. This might be a ruby mithrax crab. Typically the same purpose and behavior as the emerald.

Alfrareef · 02/01/2017, 10:08 AM

Also. Mine look similar, but not that color.

cincyjim · 02/01/2017, 10:24 AM

Check out what a strawberry crab looks like and see if that is what it might be. I have one for probably a year now with no issues.

mcgyvr · 02/01/2017, 11:02 AM

Well.. "Emerald = green"
I believe thats referred to as a "Ruby Red Emerald Crap"

A strawberry is different..

Spudsly · 02/01/2017, 11:07 AM

I was already a little gun shy about adding emerald crabs because I feel like there's often a lot of species that look like mithrax that are sold as such and cause problems. Since this clearly isn't the crab I researched I was just wondering what the consensus on it is. Should it live it's life in my sump or is it most likely ok?

kevin21 · 02/01/2017, 11:47 AM

I believe you will be just fine.

Spudsly · 02/01/2017, 11:52 AM

Ok, the area on the left side of the claw isn't the pattern or location of "black" that would make you remove it?

kevin21 · 02/01/2017, 12:30 PM

No, its when the claws themselves are black. Regardless, crabs are always hit or miss. Whether hermits, emeralds, etc. I have had emeralds for years with no issues. This ruby mithrax should be no different. If you ever catch it misbehaving, toss it in the sump where it can still live quite happily.

coralfish · 02/02/2017, 07:06 AM

Looks like a Sally Lightfoot crab

Sent from my iPhone using Tapatalk

Spudsly · 02/02/2017, 10:03 AM

I took the plunge and added him to the display. He went right to work on the rocks. I'm definitely a little nervous about him but I guess you should always be suspicious of a crab.

alton · 02/02/2017, 10:08 AM

Looks like a Red Mithrax Crab, I got a few with my KP Aquatics Live Rock. They are considered the deep water cousins of the Green. Mine will however not go after food, just sit there and eat algae and pick on the rocks all day long. They also clean up the larger bubble algae, but will not touch the smaller bubble algae.

Spudsly · 02/03/2017, 06:13 AM

So he's been hanging around this SPS and I've noticed what look like little bald spots on it. This morning I see him hanging out under it and he's definitely picking at it but I don't exactly see any damage... is it safe to say he's eating the flesh?

alton · 02/03/2017, 06:27 AM

Could be just cleaning it? I had a Flame angel that seem to always pick on my SPS, but I never lost a one, nor did it slow down its growth.

Spudsly · 02/03/2017, 06:50 AM

I agree, it didn't seem obvious to me that he was doing damage as I was watching. Despite growing really well I've never really seen polyps from that SPS (hawkins) so I guess he's not eating the polyps. Mostly I worry about the "bald spots" that appeared the same night I dropped him in. However it might be just what it looks like when new growth is about to sprout up, so I'm not sure.

02/01/2017, 09:56 AM	#2
nitr8 Registered Member Join Date: Jul 2008 Location: Lakeland, FL. Posts: 1,932	I added 5 green emeralds to my SPS tank and 4 of the 5 I had to remove because after they rid the tank of bubble algae they started sucking on SPS polyps for the slime. __________________ The solution to pollution is dilution. Current Tank Info: February 2017 TOTM

02/01/2017, 09:59 AM	#3
kevin21 Registered Member Join Date: Sep 2005 Location: Long Island, New York Posts: 2,208	That does not look like an emerald to me due to the coloration. However, the body structure and claws are extremely similar. The very basic and broad rule of thumb is if their are any black on the claws, its normally smart to remove from the tank. This crab doesn't seem to have any black. It is probably safe. This might be a ruby mithrax crab. Typically the same purpose and behavior as the emerald. __________________ Kevin Current Tank Info: Waterbox 50g, Tunze 9004 dc skimmer, Vortech mp10, Kessil ap700

02/01/2017, 10:24 AM	#5
cincyjim Registered Member Join Date: Sep 2011 Location: Northern Virginia Posts: 1,147	Check out what a strawberry crab looks like and see if that is what it might be. I have one for probably a year now with no issues. __________________ Jim Current Tank Info: SCA 150G, 5 inch sand bed, 2 Tunze 6095s, ReefBreeders v2+ 50" with 2 all Blue Reefbrites, and Continuous Water Change System

02/01/2017, 11:02 AM	#6
mcgyvr Registered Member Join Date: Sep 2003 Location: North Carolina Posts: 20,050	Well.. "Emerald = green" I believe thats referred to as a "Ruby Red Emerald Crap" A strawberry is different.. __________________ Who me?

02/01/2017, 11:47 AM	#8
kevin21 Registered Member Join Date: Sep 2005 Location: Long Island, New York Posts: 2,208	I believe you will be just fine. __________________ Kevin Current Tank Info: Waterbox 50g, Tunze 9004 dc skimmer, Vortech mp10, Kessil ap700

02/01/2017, 10:08 AM	#4
Alfrareef Registered Member Join Date: Mar 2016 Location: Portugal Posts: 405	Also. Mine look similar, but not that color.

02/01/2017, 11:07 AM	#7
Spudsly Registered Member Join Date: Aug 2016 Posts: 66	I was already a little gun shy about adding emerald crabs because I feel like there's often a lot of species that look like mithrax that are sold as such and cause problems. Since this clearly isn't the crab I researched I was just wondering what the consensus on it is. Should it live it's life in my sump or is it most likely ok?

02/01/2017, 11:52 AM	#9
Spudsly Registered Member Join Date: Aug 2016 Posts: 66	Ok, the area on the left side of the claw isn't the pattern or location of "black" that would make you remove it?

02/01/2017, 12:30 PM	#10
kevin21 Registered Member Join Date: Sep 2005 Location: Long Island, New York Posts: 2,208	No, its when the claws themselves are black. Regardless, crabs are always hit or miss. Whether hermits, emeralds, etc. I have had emeralds for years with no issues. This ruby mithrax should be no different. If you ever catch it misbehaving, toss it in the sump where it can still live quite happily. __________________ Kevin Current Tank Info: Waterbox 50g, Tunze 9004 dc skimmer, Vortech mp10, Kessil ap700

02/02/2017, 07:06 AM	#11
coralfish Premium Member Join Date: Sep 2003 Location: Hardmoney, KY Posts: 750	Looks like a Sally Lightfoot crab Sent from my iPhone using Tapatalk __________________ One leg missing and both hands free. Current Tank Info: 220 Reef

02/02/2017, 10:08 AM	#13
alton Registered Member Join Date: Jan 2005 Location: Zuehl, Texas Posts: 4,460	Looks like a Red Mithrax Crab, I got a few with my KP Aquatics Live Rock. They are considered the deep water cousins of the Green. Mine will however not go after food, just sit there and eat algae and pick on the rocks all day long. They also clean up the larger bubble algae, but will not touch the smaller bubble algae.

02/03/2017, 06:27 AM	#15
alton Registered Member Join Date: Jan 2005 Location: Zuehl, Texas Posts: 4,460	Could be just cleaning it? I had a Flame angel that seem to always pick on my SPS, but I never lost a one, nor did it slow down its growth.

02/03/2017, 06:50 AM	#16
Spudsly Registered Member Join Date: Aug 2016 Posts: 66	I agree, it didn't seem obvious to me that he was doing damage as I was watching. Despite growing really well I've never really seen polyps from that SPS (hawkins) so I guess he's not eating the polyps. Mostly I worry about the "bald spots" that appeared the same night I dropped him in. However it might be just what it looks like when new growth is about to sprout up, so I'm not sure.