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texasfootball21
08-23-2007, 11:19 PM
Is an emerald crab suited for a beginner? I will soon start my first marine tank and would love to add a emerald crab after it is a bit more established. How hard are they to keep? What's the best thing to feed them? Are they a threat to other crabs? Can you keep more then one? How long should you wait before adding to a 36 gallon FOWLR with some inverts? And please post any experiences you've had, good or bad, with this crab, thanks!

R. Deschain
08-24-2007, 12:02 AM
I've only had my Emerald Crab for about a week, so not a lot of experience. He has knocked a few things over, so would suggest securing things down. From what I've read, they are general detritivores, but show a preference toward algae (including bubble algae) No special feeding is required.

Hope others with more experience can answer your questions more thourougly.

tim
08-24-2007, 12:35 AM
I think they are great to have as a clean up crew. I would wait before adding any though until the tank has matured for a while IMO

Seahorsedreams
08-24-2007, 01:56 AM
My tubastrea started to look really bad for awhile. It turns out our time consuming spot feeding was being taken care of by the emerald. He had ran out of algae to eat. So, if you don't have algae make sure a little food goes he way during feeding time or he will starve. We now hand him a sheet or nori when we feed the tubastrea and he is always sitting there waiting.

texasfootball21
08-24-2007, 01:17 PM
Thanks for all the help. Im a 36 gallon how many should be added?

Seahorsedreams
08-24-2007, 03:10 PM
I would only go with one in there.

lReef lKeeper
08-24-2007, 05:09 PM
i would only go with 1 too. they get pretty big.

texasfootball21
08-24-2007, 05:31 PM
Okay, only one, thanks.

Pescaiolo
09-02-2007, 10:54 PM
Emeralds will farm bubble algae. Don't get rid of all your bubble algae(if you have any to begin with) and it will grow its own food along with whatever it will eat that you feed to the tank. Its actually pretty neat to watch them grow their own food. :)

salt-rookie
09-02-2007, 11:07 PM
Mine clips tails off of Cleaner Shrimp! I would LOVE to get rid of mine!!!!!

ryandlf
12-04-2008, 10:34 PM
I know this is an old post, but I just had to comment...I have a small emerald crab because the LFS told me it would take care of some hair algae. Well...yes, it does eat hair algae, but in my particular situation, not enough to really control and minor outbreak in a tank. Still, they are very cool. Anyone ever hear of where's Waldo? It can be kind of like that when you are searching your rock trying to find that crab, they blend right in.

On a side note, mine used to be very active and for the past day or two its just been sitting in mostly the same spot. Is this normal?

CarmieJo
12-06-2008, 03:09 AM
I don't know so lets :bump: this back to the top of the list.

THEJRC
12-08-2008, 10:40 AM
On a side note, mine used to be very active and for the past day or two its just been sitting in mostly the same spot. Is this normal?

I'll weigh in here, most likely it's molting, it's also possible if there are multiples that it has or is going to spawn. The females can only spawn during a molt and it extends the average molt process (with obvious reason) as they have to release the pelagic larvae into the water column before exiting the shell.

As far as how many in tanks, the size of the tank is not so much the key than the environment. So long as there is ample food supply (they will eat all manner of scavenged food including flake and the like) and enough hiding spots for all of them. I have 8 in a section of my breeder rig that's approximately 10 gallons and they're living pretty healthy (in fact they spawn pretty regularily). But once again, this system is high nutrient and very very well fed. Many of our emeralds are fed by hand (it's hilarious to watch them wave their little crab claws for food).

As far as the "how safe" questions, it's much like a dog or anything else. I've seen a few that were agressive but the vast majority are extremely docile and great little inhabitants.

Before the breeding questions come up I'll go ahead and jot down my notes as I've been trying to crack the code on these buggers for a while:

* A slow rise in salinity over a two week period (2-4 points) followed by a quick bounce back down (2-4 points again) thus far has consistently triggered spawning within a few days

* The larvae are visible with the naked eye within the water column but are extremely fragile, removal from broodstock system and placement into a Kreisel type system is most likely required for any rate of survival

* Even the docile cleaner shrimp seem to love feeding on the larvae, this means that for survival the grow out tank should not contain any predators such as amphipods, shrimp, etc. I have not seen mysids or any of the larger copepods preying on larvae (most likely due to size) however I havent had any survival rate to speak of with larvae grow out due to other inhabitants.

* I have a feeling the salinity bump to trigger spawning may be causing problems with larvae grow out. I'll have to play with this one.

ryandlf
12-09-2008, 12:33 AM
Interesting info...
Well a slight update on my Emerald...lets just say he's back to scurrying around the tank (who knows why he/she was being lethargic for a couple days. Maybe I was just being paranoid.) I think this is a good thing, but its EXTRA emerald these days...very green and shiny. Looks can be deceiving though...so the big ? Is this very colorful green a good thing?

pvtdonut
12-09-2008, 10:21 AM
I dont see why it would be a bad thing.

i know after my scarlet shrimp molts, it comes out in a bright bright shiny red color. It has never affected anything before.. I notice that usually before he molts, his shell starts turning a palish red, almost white in some spots... mainly in the (what would be) spine.. usually within a day or two, ill see his shell laying under a rock and the shrimp back in his usual spot lookin better than ever. also, any limbs that have been removed or lost, grow back. which i think is awesome.

THEJRC
12-09-2008, 10:32 AM
I think this is a good thing, but its EXTRA emerald these days...very green and shiny. Looks can be deceiving though...so the big ? Is this very colorful green a good thing?

Yup! It's a shiny newly created shell! I bet if you look around in the tank you'll find the old one hanging around. Often when people see their first crab or shrimp molt they think the critter has died. It's just the old shell that's been discarded (legs and all even!). In fact it's highly likely that the "lethargic" crab you saw was in fact the molt itself and the crab was hiding in a hole waiting for it's new shell to form!

Often if molting takes a few days it's a good idea to check your iodine levels, iodine aids the molting process and if levels are low the process typically takes longer.

bbl_nk
12-09-2008, 07:36 PM
I have two EC's in my 75g and they're definitely shy. I see them most of the time at night and ocassionally on the sand bed. I call them Fritz and Hans...Hans only has one pincher, so his name is "Hans Ein Zeiger." When I added a small rock with 7-8 Zoa polyps one came out and started picking at it. I raised it up on a plastic cup to keep it safe. They don't seem to bother my SPS coral frags, so I think I'm going to keep them. I have a hitchicking black mythrax crab that i've only seen 2-3 times. I need to bait that black one tho, not sure what to do with him.

THEJRC
12-10-2008, 10:58 AM
the blacks seem to be more territorial but tend to hide a lot more, you almost never see them. Ten to one on the zoanthids they were picking at algae on the rock or scavenging food from the polyps. I've never seen them actually eat any corals but like anything else in this hobby it's entirely possible you got that random rare one with all the other habits they arent supposed to have...

ryandlf
12-10-2008, 11:15 PM
Funny you mentioned thinking that many think their crab has died. I'm still quite new to the hobby and right before you so graciously advised me on this whole molting thing, I found an empty crab shell and an empty shrimp. I found the two creatures in my tank alive and healthy and I didn't know what the heck was going on. I figured "well maybe the previous owner has more in there and they died a long time and got wedged under a rock of something and now their coming out." Oh the crazy thoughts that occur when your experiencing all of this for the first time.

Anyways, some really awesome advice guys. Only other question I can think is how big will these EC's get and how fast will they get there. Right now mine is probably only about an inch across.

THEJRC
12-11-2008, 12:14 AM
average full size is around an inch and a half claw to claw for the green varieties, the blacks typically get larger though I've never personally seen them larger than two and a half inches across. Individual results may vary, this statement has not been evaluated by the FDA.

bbl_nk
12-11-2008, 02:44 PM
Too funny THEJRC! Yeah i knew I had a hitchiker when I found two molts MUCH smaller than my EC's. Then one night I saw it! One claw coming out of a rock and caught a corner of its shell. I've also noticed EVERTHING goes nuts when i add something new. I adding in a GSP and the Zoa's and the EC's came out, the hermits went nuts and the Nassarius snails even came out. Its crazy how they can all sense the chemical scent of the corals and wake them up.

THEJRC
12-12-2008, 01:18 AM
he he, our black one was a mystery for a long time, he didnt show up at all for months then we saw a claw.... naturally in my style of reefkeeping (feed it till it's fat) we start feeding the "claw" we still barely get glimpses but when we do all we know is it's huge!!!

then one day we added another EC in an odd bit darth (the name we've dubbed the black one) came out and they began to have a little fight.... oddly we've added EC's before and after with no problems, just the one that ole darth didnt like I guess. We've since relocated darths nemesis (now dubbed luke of course) to another system.

I cant complain, excluding any unknown larvae that may have survived we have around 14 crabs now divided between three tanks and no bad instances to speak of at all (other than the duel mentioned above).

CarmieJo
12-12-2008, 01:43 AM
OK Joe, I HAVE to ask, did they use light sabers to duel with???? Do they make the light saber sound under water? :D

THEJRC
12-12-2008, 02:48 AM
OK Joe, I HAVE to ask, did they use light sabers to duel with???? Do they make the light saber sound under water? :D

unfortunately not, it was more of a "luke I'm your father and three times bigger" a few claw grabs and then swoosh, luke was saved by the millenium falcon (ala hand).

sad thing is, I'm not even a star wars fan! The nephews though, insist on star wars names.

Even worse.... Luke is actually Leia and has been the focus of many of my spawning studies.... we've yet to capture and sex darth, and a new black mythrax specimen was introduced into a solitary section last weekend (female) that I'm considering adding to darth's domain in hopes of pairing.... not sure though.

and of course in edit, the avatar you see is actually a portion of one of lukes molts (hah hows that for back on topic). The arms however were accidentally removed from a banded shrimp during transport....

Carty
12-13-2008, 09:32 AM
i've got 4 EC's I see them MAYBE once a week and never all at once... I always think they have died and then out of nowhere ill see 2 or 3 of them within a few seconds

bbl_nk
12-13-2008, 10:02 PM
Well, was re-aquascaping my rocks when I saw the little black bugger. I popped him out with a small bamboo skewer and realized after a made a noise he was still in the rock. Long story short, I ended up losing both claws and a leg off him so I ended his misery as humanely as possible.

I hate killing kritters, but considering I didn't even want the guy and reading bad stuff on them...I am a bit relieved. Now I'll just have to wait and see about the EC's. Didn't see them at all today. Hope I didn't bury them.

R. Deschain
12-13-2008, 11:34 PM
I have recently added reinforcements to my CUC including two emerald crabs. One of them has a reddish color...this is an emerald crab right??

YouTube - Psychojam's Reef 12-13-2008

rroselavy
12-15-2008, 08:46 PM
I have recently added reinforcements to my CUC including two emerald crabs. One of them has a reddish color...this is an emerald crab right??

YouTube - Psychojam's Reef 12-13-2008 (http://www.youtube.com/watch?v=KDckSArmE0I)

I ordered a EC from John Maloney (reefcleaners.org) and I received a red mithrax crab instead. John was very nice about it, offering a refund - but I was fine with it. Looks just like an emerald, hairless bumpy back, hairy legs, but orange-red instead.

He chilled out in my QT for a few months, chomping on a lot of algae (including some macros I paid for :eek:). The first time he molted - I swear - he was at least 25% bigger afterward, with disproportionately huge Popeye claws. Arrrggh!!! I need to put a little anchor tattoo on him...

Now he hangs out in the DT. He's definitely works on the algae, but I cannot tell if he is eating the HA or the diatoms on the HA. He's always working on something.

Sometimes when my Fourline wrasse passes close by, he reaches out in slow motion with his claws, perhaps as a warning. By the time his claws are fully extended the Fourline is already on the other side of the tank... LOL - I think Frankenstein moves faster.

Like other crabs, he is an opportunist. A flipped over Astraea can be irresistible for him. I also noticed him once or twice at the base of my Poccilopora, picking at a polyp. Haven't seen any damage yet however.

THEJRC
12-16-2008, 10:20 AM
I have recently added reinforcements to my CUC including two emerald crabs. One of them has a reddish color...this is an emerald crab right??


indeed it is! Color variations are normal for the mythraculus sculptus species, look for the same features. Scooped claws, the hairy legs, wide set black eyes. Often the reddish ones will turn black with age and time.

To enforce Rroselavy's post, often the red and black variants seem to be more shy about hiding but a little bit more territorial (waving off fish and other intruders is normal). I've yet to see or hear any confirmed accounts of them eating any corals but yes, they do tend to re-decorate their own territory on a whim. If you place something in or near it's hole it's bound to move it where it wants it to be.... I've had many such arguments about placement with our first black variant before giving up and leaving his cave opening free of decoration.

rroselavy
12-17-2008, 02:50 AM
Here are a few grainy pics of my brute from tonight's photo op:

http://homepage.mac.com/svanzo/.public/081215/mithrax1.jpg

http://homepage.mac.com/svanzo/.public/081215/mithrax2.jpg

rayme07
12-17-2008, 03:58 AM
That's very :cool!: looking, nice color red on him. Thanks for the pics. :)

THEJRC
12-17-2008, 10:20 AM
he does look slick!! Cant really tell for sure from the pic but given the pronounced "tower" on his belly there he is in fact a he as well. He should be a great little inhabitant. Cool for sure

tev478
06-14-2009, 07:33 PM
I have had a EC in the past. He turned white and stopped moving, i pulled him out of the tank. Prooceeded to open him up and there was all his insides. So i thought he died.After going to all the store guys i speak to i thought i didnt feed him right and he died. I have a new one and i almost did the samething. I the morning i noticed alot of the sand snails all over an object in the sand. I couldn't see what it was because of teh snails. I have my pokin stick for when a hermit crabs doin something i dontlike. I grab that and knock the snails off. It was my crab. I was pissed. I feed him by hand with small slices of frozen algea food. I had to leave for work but i tried to pick him up, the stick has a little shovel on the end, but he kept slipping off. I come back from work and and his body is no where to be found. Then i found his main top shell in the sand completely empty. So i think my crab is a female from the info here. And ive always want to see him shiny. Thanks:up:

CarmieJo
06-14-2009, 11:22 PM
Hi Steve and :welcome: to TR!

Polks
11-13-2009, 10:46 PM
Just to throw my beginner's 2 cents in, I was able to bait my Emerald Crab with a pinky-tip size pc of frozen scallop. It has worked every time. Day or night, it shoots towards it, and I cover it with a container to isolate it (this is now, when he's under suspicion of destroying coralline :)).


I know this is an old post, but I just had to comment...I have a small emerald crab because the LFS told me it would take care of some hair algae. Well...yes, it does eat hair algae, but in my particular situation, not enough to really control and minor outbreak in a tank. Still, they are very cool. Anyone ever hear of where's Waldo? It can be kind of like that when you are searching your rock trying to find that crab, they blend right in.

On a side note, mine used to be very active and for the past day or two its just been sitting in mostly the same spot. Is this normal?