Emerald Crab Advice

[texasfootball21]

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]

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]

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]

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]

Thanks for all the help. Im a 36 gallon how many should be added?

[Seahorsedreams]

I would only go with one in there.

[lReef lKeeper]

i would only go with 1 too. they get pretty big.

[texasfootball21]

Okay, only one, thanks.

[Pescaiolo]

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]

Mine clips tails off of Cleaner Shrimp! I would LOVE to get rid of mine!!!!!

[ryandlf]

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]

I don't know so lets this back to the top of the list.

[THEJRC]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

OK Joe, I HAVE to ask, did they use light sabers to duel with???? Do they make the light saber sound under water?

[THEJRC]

OK Joe, I HAVE to ask, did they use light sabers to duel with???? Do they make the light saber sound under water?

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]

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