emerald crabs?

[m3rma1d]

i feel like i'm posting a super lot today, but better to post than make a big mistake hey??

how are emerald crabs? what do they eat? do they get along good with everything? do they die easy?....etc?..you know the drill

[ShirleyM]

Hello there,
Emerald Crabs eat bubble algae. They are harmless, and sometimes they last for a long time and sometimes they don't....that's my experience, anyhow.

Shirley

[iceboxman]

Mine didn't last long. Oh well.

[Calvinc4s]

The only time I ever seen mine is in the middle of the night with the light off; They are cool though.

[Flatfish]

I got five as part of a cleaner crew. Two died off quickly. The interesting thing is the remaining three lasted for more that a year. Then all of them died practically at the same time. I don't know what caused it but the other crustaceans (sally lighfoot, hermies added at the same time) are doing well today. I think they are a bit of a mystery. They can be very aggressive especially during feeding. These things are normally quite small. Mine were no more than ½” at the body. I had one during feeding reach out and grab a 4” sleeper goby and not want to let go. When I intervened the crab backed into a hole folding the fish in half. A real national geographic moment. He finally let go, but the goby never recovered. This is probably a very rare event, but it did happen. I did not have good experiences with them and would probably not get another.

[Macaw Guy]

Dr. Ron says that at least 2, maybe 3, different species are being currently sold as emerald crabs.

The reason this is important is that TRUE emerald crabs (scientific name unknown to me...) are largely herbivores. However, the other species which are being "mislabeled" as emerald crabs are much more bothersome, and you wouldn't want them in your tank since they'd turn into pests. (You thought your peppermint shrimp vs. the worm was bad!!)

Plus, there's no really easy way to tell the difference between the 3, so it's kinda hard to ensure you're getting the right critter.

I'd stay away from all crabs....Just my honest opinion. I made the mistake of acquiring 12 blue-leg hermits and all they do is cannibalize each other and steal snail shells. They do look cool, but the snails do more good for my tank so I'm banishing the hermits to the nether regions.

Andrew

[Jimbo]

Hi, Just bought one and he is about 2" across. He eats bubble algea but will eat shrimp at feeding time. Here's a pic. He is very active even in the daytime.



Hope this helps

[FishDaddy]

I've had mixed results with Mithrax crabs. I had one that did eat Valonia but also acquired a taste for Coralline after the Valonia was gone. Later, when the Valonia reappeared, I put two in; one disappeared soon thereafter and the other did his job but eventually disappeared as well after 6-7 months. The last one ignored the Valonia but decimated all the small feather dusters!! I removed him.

I've got the Valonia back (Why does it reappear after being apparently eradicated??? ) and am going to try Mithrax again.

As Andrew reported, Dr. Ron has said there are more than one species being sold. The "good one" is supposed to have orange-red on the inside of the elbows of the main claws.

Dick

[Macaw Guy]

Thanks Dick - I didn't know how to tell the difference!

I'm still sticking to the South Park principle:

"Crabs are bad. And if you have crabs, you're bad. Mmmm-Kay?"

[Piero]

viciously attacking and devouring a linmpet(stomatella) snail last night. Little ******, get back to that algae!

[hooked]

I have seen my emerald eat bubble algae and pretty much pick off anything on the rocks he feels like I have not had one live past 2 weeks so I hope with the increased lighting and algae growth my 2 I just got will make it.

[Spanky]

Okeee Dokeee!

We've actually caught all six (not two or three) of our different Mithrax going out of here labeled as "emerald". The proper name for emerald crab is green clinging crab - Mithrax sculptus. The easiest thing to look for is also the most obvious, emerald green. Not muddy green, olive green, brown green, no bands, no orange, certainly no red. Also, I guess you would call it their forearms, are not hairy but smooth like porcelain. No bumps on their claws either.
They love Dictyota too!

HTH
Jerel

[FishDaddy]

Jerel,
What about the info that Mithrax sculptus has a bit of color on the inside of it's "elbow" on the claw arms??
Dick

[chewie]

I would like to know as well. I have 1 emerald and he has the red patches on the inside of his elbows and he does have bumps on his claws. he has always been on his best behavior!!! now Jerel has me confused..........

[Spanky]

now Jerel has me confused..........

It's a dirty job, but someone has to do it.

I believe you are referring to Mithrax verrucosus, they have a reddish to bright red patch right behind their foreclaw and bumps. They also have smaller claws. Sometimes they show a little more red on their carapace too.
I'm holding one right now.
I wouldn't worry too much about having one, like sculptus, they also stay small (about 1") and are heavy algae feeders.
Oh, while I'm looking at it, look around the edge of the carapace. In M. sculptus the "spines" should be blunt. In all others, either a lack of spines or very pointed spines.
BTW - sculptus pinches harder! Don't try this at home!!