FAQs about Emerald Green, Mithrax/Mithraculus
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FAQs on: Mithrax
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white powdery look... On Mithraculus, snail...
I have had 2 emerald crabs die. Both developed a white powdery looking substance
on their bodies.
<Precipitation? From... supplement use likely>
I have 6 snails and a few have the same substance, 1 extreme. I have a pajama
cardinal, a banded coral shrimp and a cleaner shrimp with no apparent issues.
<Stenopids will eat all other small crustaceans, snails.... were the bodies
intact? Are you sure these weren't/aren't simply molted exoskeletons (the
Mithraculus hiding?). Bob Fenner>
Re: white powdery look
Thanks for the reply. No supplement use. Watched the crabs slowly die.
<Slowly? How much time; please describe their behavior. What do you feed?
Have you read on WWM re this species?
The one snail is covered with this. Would a picture help?
<Yes! As close up, highly resolved image as you can provide. B>
Red Emerald Crab; ID, comp. 9/15/15
So I will begin with the disclosure that I know emerald (Mithrax) crabs
have a dubious reputation as reef tank inhabitants.
<Mithraculus are opportunistic; like other Decapods>
I don't hold opportunistic behavior against them but one of them is heading for
a new home. My inquiry is in regards to your opinion of the traditional emerald
crab versus the, sold by online vendors and my lfs, red emerald crab. He(big
red)is described as being identical to a traditional emerald crab save for
coloration. Do you have any knowledge of this crab variation or his possible
variation in behavior?
<.... some folks purport this is also Mithraculus sculptus>
There are three Mithrax crabs in my 65 gallon reef, one is to tiny to be the
culprit, and one each of a large red and large green Mithrax. Just trying to
make the best decision, without hard evidence, as to who is tearing my green
star polyps off from the base. I did consider the health of the coral and
definitely seems to be some clawed species is clipping the polyps off leaving
the purple base intact. Any input as to the potential difference in culpability.
I did search for these red Mithrax variants and found little evidence of them on
your site. Hence the email and appreciation of your opinion.
<Both, all are suspect. I'd remove them. Bob Fenner>
Emerald crab issue. 4/18/11
Hello, thank you for taking time with this issue!
My system is a 125 gallon system with one Clarkii species clown,
Condylactis Anemone (saved from horrible treatment at the LFS), and two
damsels. I also have one Mithrax species crab.
<Mmm, some members of this genus (Mithraculus for some now) do get
quite large, predaceous>
My issue is that the crab seems to have a tentacle growing from one of
its lower legs!
It's known to fight my anemone for the occasional fresh piece of
seafood, so I know it's come into contact with the Condylactis on
My obvious idea is that he got a tiny piece of the foot stuck in a
joint of that leg and that piece is regenerating a new anemone.
However, I'm wondering if it could be an illness or parasite,
hence writing you today. In lieu of a picture (which I don't have
access to) I can describe it.
It's *exactly* like a smaller version of the pink tentacles of my
It grows a few millimeters per week, and doesn't seem to be
affecting the Mithrax at all.
Water parameters for nitrogen compounds are perfect, pH is 8.3, and I
dose the tank with PurpleUp weekly.
<I either wouldn't worry, or remove the crab/tentacle together
or separately... Let's see, that about covers all contingencies.
Oh, yeah, read here: http://wetwebmedia.com/mithraxfaqs.htm