Emerald Crab info

[OCDreefer]

Do these guys bother Gobies and other sand dwellers??

 

[jrgilles]

I had a pair of these. One was a ******* and went after LPS and sand dwelling fish. The other was fine. I guess they 'should' be safe, but it really depends on the crab.....

They are cheap though, so you could always test them out and if one of them decides to misbehave, banish it to your sump or fuge or something. The trouble maker I had was very easy to catch. I just put a glass into the tank witha piece of squid in it. It couldn't resist the bait. Caught it in less than a minute.

 

[CT12]

I have four crabs in my 90 gallon with a sand sifting goby (orange spotted/watchman) and several other fish. They get along fine. They put their claws out to scare fish off but they don't actively pursue the fish I have. They typically dart back under the rock work when a my goby confronts them. Make sure there is enough in your tank for the crabs to eat. I am running low on algae and my crabs are becoming a little more adventurous. I've been able to hand feed them small sheets of algae and they all come out when I'm feeding the tank.

 

[WABlonde]

We have just one in our 75 gal and he's growing fast (I hear they don't get big). We absolutely LOVE him, he's one of our favorite things in the tank. He doesn't bother our goby or other fish. He's happy and busy all day/all night. Fish also have no interest in him.

We did have a scare about 2 weeks ago - thought we had a dead crab. Couldn't figure it out. Then saw him later that night or next day - he had molted. I guess I wasn't aware that they did that. Was cool and we were so impressed with his size difference.

Thought about getting a second emerald but I suppose I didn't think that they might not all be as great of a tank mate as Mr. Crabs. Guess I don't want to press my luck.

Highly recommend though!

 

[LeslieH]

Most people are very satisfied with their emeralds. Occasionally one will go rogue but as CT12 said, if they're hungry they get more adventuresome not only about confronting fish but going after other types of food. Make sure you get a real emerald though! Mithraculus sculptus (also sold as Mithrax sculptus). Some LFS sell what they call "black emeralds" which aren't even in the same family let alone the same genus & species.

 

[bigblue141]

Are "Strawberry Crabs" any better than the Emeralds?

 

[WABlonde]

Reading up on the Strawberry Crab. It sure is cute and sounds like it wouldn't cause problems. Curious if anyone has experience with them.

 

[bigblue141]

I had several strawberry crabs and they are cool looking when you see them maybe once a month, just thought I'd ask the expert if they were as good or better than the emeralds

I know that all crabs can get crabby

 

[LeslieH]

Strawberries haven't been around as long as emeralds so there isn't as much collective experience to go by. They seem to be on the same level as emeralds in that the majority of them are inoffensive but occasionally one will prey on other animals. Emeralds are more visible while the strawberries tend to disappear into the rock work.

Nearly every commercial site uses the same language to describe them which means they don't actually know - they're just cribbing from one source. So they say reefsafe, enjoys eating algae, will eat uneaten food left by fish, needs protein, and suggest supplemental feeding of nori & meaty foods. Protein? Meaty foods? So they're omnivores, not strict herbivores.

Most posters have said that their strawberries are harmless & can only be seen at night. A few have complained that the crabs have gone after fish, shrimp, & other crabs. Not surprising - if the pictures on the sites are any indication there's a variety of crabs being sold as strawberries. Check out the differences between these pics
Strawberry Crab
Strawberry Crab

The first pic is right. The second is clearly a different type of crab - see those long eyestalks?

 

[bigblue141]

The one from Seascape looks like some type of fiddler/meat eating crab It just looks mean...

Crazy that not much is known about strawberry crabs. I had 6 or so, rarely saw them, but I didn't have fish or shrimp come up missing either...

 

[OCDreefer]

How do you tell a good emerald from a bad crabby.

 

[Rhodes19]

How can you positively ID an emerald crab from other crabs? I've seen brown and or brownish green crabs at some lfs being sold as emerald crabs and images on google show a range of colors from red, orange, bright green, dark green, blue.... Thanks.

 

[LeslieH]

Emeralds are a single species, Mithraculus sculptus. An older name for it which is still commonly used is Mithrax sculptus.

http://corvand.net/xoops/modules/bentos/bentos_pic_view.php?Bentos_ID=72
Normal color ranges from pale whitish-green to dark blackish-green; most are clearly green. This one is a bit brown but the image shows off the shape of the carapace and the two big spines on the legs carrying the claws characteristic of the species.

Unfortunately a lot of crabs are sold under the wrong names. If the results of your google search came in the same order as mine, then nearly all of the crabs in the first 5 rows are emeralds. The exceptions are a freshwater Geosesarma in the third row, 2nd from right, and a black xanthoid in the fifth row, 3rd from right. There are more non-emeralds as you go down the page. Unless an algae or something else is growing on the shell an emerald is never red, orange, true blue, black, etc. The crabs that are sold as orange, red, & black emeralds usually aren't even in the same family.

 

[Rhodes19]

Cool Beans!! Thanks Leslie, I appreciate the information and the awesome picture. I've been thinking about getting one for my 180 to deal with some HA and bubble algae and as part of the cuc. I should have an easy time picking it out. Are they safe with shrimp?

 

[LeslieH]

Usually reef safe & shrimp safe. Occasionally you'll read complaints about one going after other livestock - just read post #2 - but for the most part they're inoffensive grazers.

 

[Rhodes19]

Usually reef safe & shrimp safe. Occasionally you'll read complaints about one going after other livestock - just read post #2 - but for the most part they're inoffensive grazers.

Thanks Leslie, I'm going to give one a try.

 

[Rhodes19]

Picked one up last week and haven't seen her since. Do they tend to hide?

 

[WABlonde]

Ours hid when he was molting. But otherwise he usually isn't far and always very active.

 

[Herefishyfishy]

They are best seen in the afternoon and evening.
I have never had one go rouge untill recently - CAUGHT ONE TEARING CHUNKS OUT A DENDRO COLONY!

 

[Rhodes19]

Ours hid when he was molting. But otherwise he usually isn't far and always very active.

Hi WABlonde,

Thanks, I'll keep my eyes open for her. She is still new to the tank.