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Crab Identification: Fiddler Crab – 10/15/09 Hi :) <Ah, bonjour Marie, Lynn here today!> I received yesterday 2 little red crabs from the Philippines and I'm not sure what they are because of the eyes. I think they may be fiddler crabs... <You’re right. The overall shape/length of the stalked eyes and sharply pointed carapace seem to be fairly common within the semi-terrestrial fiddlers in the genus Uca, family Ocypodidae. The closest I can find is a photo of something alleged to be Uca arcuata (see this link: http://www.geocities.com/rainforest/canopy/5280/philip.htm ). Unfortunately, I can’t confirm the ID. Either the color/pattern varies quite a bit (as shown at the above link) or they’re different species entirely. Apparently, in the Philippines, these are mainly mangrove/shallow water/intertidal crabs that make their burrows in the mud and sand. Interestingly enough, I’ve seen a similar species being offered for sale on the internet, listed as a “Red Burrowing” crab in the genus Uca. > ..even if they don't have the oversize claw... maybe they're female. <Yes, my thought as well.> I sent you a picture, maybe you can help me with this identification. <I sure wish I could give you a solid ID to species level, but there are just too many possibilities and not enough available information on the ‘net and within my research books.> I don't want to give bad information to my customers. <Good for you! I wish all merchants were this conscientious! Unfortunately, I have to add that these little crabs should not be kept in a fully submerged marine system. They’d do much better in an environment more closely resembling they’re natural habitat (mixed land/water). For more information on this group of crabs, please enter the terms (Uca or fiddler) into our Google search engine (http://www.wetwebmedia.com/Googlesearch.htm). I’ve seen several posts regarding solid red fiddler crabs with reports of them being very reclusive. Apparently, once added, they tend to burrow/hide and not come out much. In Barnes’ Invertebrate Zoology (sixth edition, pg. 717), it states that tropical species of this genus “tend to be active only during diurnal low tides”. That’s not a whole lot, even in the wild! Also, they’re still crabs and basically opportunistic, so hobbyists will need to keep these well fed to discourage picking/killing of desirable livestock.> Thank you <It was a pleasure, Marie.> Marie <Take care, LynnZ>

Fiddler crabs in sea water... Not  11/08/07
Hi there, I am trying to set up a fiddler crab tank for a high school research department. I've seen a lot of references to the brackish water these crabs need -
<And land... most are only part-time aquatic, if then... live in/on mud and sand>
but the crabs we have were taken at the beach. Should they be in pure seawater?
<No... land/sand... with some water to moisten themselves>
Currently the water we are using is from the same beach we found the crabs, but I'm not sure if this is an optimal condition. Any information you can provide would be greatly appreciated. Thank You!!
Andrea Beatty
<Andrea... "Woman of the sea"... fitting name, eh? Bob Fenner>

Fiddler Crabs
I have a 55 g. marine aquarium with 45 lbs. LR. I was recently given a VERY surprise present of a fiddler crab. I've never seen one of these mentioned in any marine article. 
<On our site: http://wetwebmedia.com/swcrabs.htm>
What do they eat? 
<Meaty bits of this and that>
Will they harm my fish (I am
planning on a tank of blennies, gobies and other small fish) or invertebrates (snails, an emerald crab, and fan worms)?
<Slow, sedentary to sessile invertebrates may be in trouble if your crab gets hungry...>
And how will I keep this guy happy? 
<Need to have a place to get out, dry a bit... and cover to hide in, reharden their exoskeleton during molting events. Bob Fenner>
Thank you very much for your time.
Mike Rathwell

Fiddler Crabs?
Hi. Thanks for all your previous help in the past, both directly and through the creation of this site.
<You're welcome>
My problem is this. I have a 35 gal tank that I added 10 Trochus and 10 Astrea snails to about a month and a half ago. Since then they have slowly died off to the point of about six. I find many upside-down on the sand bed, and, up until now, I had thought they had fallen off the Live Rock. However, I had failed to realize that I had been given a "gift" of a Fiddler Crab about two weeks prior to the addition of the snails.
<The "Trojan" gift crab...>
At least that's what it was called, and it looks like one (has the eye stalks, but doesn't have the one, large claw--I'm assuming this is because its female. But the Bad News Bears and Walter Matthau taught us what happens when one assumes). 
<Well put>
After the addition of the Fiddler, it disappeared for months and I believed it to be dead due to lack of a place to dry out.
However, a few nights ago I found it out and crawling around the rocks. My questions are these: Is this crab causing the demise of my snails? 
<Maybe... are their bodies missing?>
Will it hamper my plans to add more invertebrates (mushrooms, leather corals, star polyps, feather dusters, shrimp)?
<Maybe... I would pull it>
If it is...then how do I get rid of it because I haven't seen it except for that one night? Please excuse the long
email, and thanks very much.
Michael Rathwell
BTW Kingsley from Aquarium Arts in Phoenix says hello.
<Ah, say hello back for me please. I would "bite the proverbial bullet" and drain, take out the rock... and remove the crab at this point. Luckily a thirty five gallon is not "that big". Please see here: http://www.wetwebmedia.com/movingaq.htm
re input on "moving" aquariums, about the same list of steps, tools, materials as you'll be doing. Bob Fenner>

Re: Fiddler Crabs?
Thank you again. The snails did have their bodies removed, but could this have also been from decomposition?
<Not that quick... a few days...>
In response to your moving idea, could a trap not be rigged up with a little bit of bait? 
<Yes... a few types described on our principal site: WetWebMedia.com>
I have seen these mentioned on various internet sites for the removal of pesky bristleworms, violent
Mithrax crabs, and other things. Would this sort of thing work for Fiddlers?
<Possibly>
Seeing as how the residents of my soon-to-be mini-reef are only 2 red Firefish, 1 smith's blenny, 1 featherduster, and 6 (numbers slowly declining) snails the moving shouldn't be a problem, but I would rather not mess with restarting a tank (thoughts of re-cycling and ammonia spikes sicken me, <Shouldn't have to be recycled... just put back what was in there... including much of the "old" water>
especially when only 1 week away from putting in the first corals). And to think...all of this work for a $4 crab! Thank you for your advice and help.
Michael
<Be chatting. Bob Fenner>