Crabs in Live Rock

[Waterbury Guy]

I've noticed (3) crabs in my tank that have hitchhiked in with my live rock. Only see them at night. 2 are pretty small (about the size of a pinky fingernail) and seem to be actually eating the rock. The third is quite a bit larger, at least the size of a quarter and never seems to leave his cave. I know there are millions of crabs, but here goes a description. Seem to be the exact color of the live rock, 2 claws that are the same size, and legs are kind of "hairy". They haven't harrassed anyone, but I really don't have anything in my tank. Should I give them the benefit of the doubt or get rid of them now.

[c_lou]

Waterbury Guy -

IMO I would remove them now while you have very little in your tank. Just about every hitchhiker crab is looked at as a bad guy. YOu have to remember crabs are oppurtunistic(sp?) scavengers.

Just thowing in a couple pennies.

Corey

[DgenR8]

Crabs in general are not really desired in a Reef. There are exceptions, but they are not what you usually find sneaking into your tank with Live rock.
A good indication of wheather or not a crab can be trusted is his claws, if they are serrated, like a steak knife, they are designed to be destructive. Can you get a good look at the claws??

[Nanook]

I had a lot of these crabs with a batch of Fiji rock a while back. I read that crabs were omnivores and that these particular crabs had claws with points and red eyes. Since I had so many, I hunted them down like the mangy dogs they were and eliminated most of them. I still have one in my tank, but I have given him a reprieve as he is the only one I ever see. FWIW,

Nanook

[Nagel]

In my experience, hitchhiker crabs are BAD.

Serrated claws, hairy legs and red eyes are indeed Satan on earth.

I would remove them before they break your heart by eating your favorite fish that you haven't put in there yet. They have a knack for doing that. I know, they did it to me last year. No more hairy rock crabs for me, now or in the future!

[blouden]

I got one particular hitchhiker that came with my LR that I have been trying to catch for about 3 months now. Yes, I am ashamed to admit, the crab is apparently more intelligent than I....

It was 1/2" when I first saw it; now its body is now over 1.5" across, red, harry, real mean looking. and only comes out in the dead of night. It has the body shape of a fiddler crab but no real obvious shell to speak of. I have not been able to get one good pitcher of it.

Anyhow, it is in my largest piece of LR that is a good 7-8" in diameter. The LR also has some gorgeous emerging coral on it which I don't want to kill in the process of getting this crab out.

I've tried numerous traps, tweezers, etc. but this sucker is very fast and retreats even in the dimmest light.

Other than dynamite, any suggestions? :confused:

[blouden]

I got one particular hitchhiker that came with my LR that I have been trying to catch for about 3 months now. Yes, I am ashamed to admit, the crab is apparently more intelligent than I....

It was 1/2" when I first saw it; now its body is now over 1.5" across, red, harry, real mean looking. and only comes out in the dead of night. It has the body shape of a fiddler crab but no real obvious shell to speak of. I have not been able to get one good pitcher of it.

Anyhow, it is in my largest piece of LR that is a good 7-8" in diameter. The LR also has some gorgeous emerging coral on it which I don't want to kill in the process of getting this crab out.

I've tried numerous traps, tweezers, etc. but this sucker is very fast and retreats even in the dimmest light.

Other than dynamite, any suggestions? :confused:

[Waterbury Guy]

Not sure, I got one of the three with a pair of tweezers. The one I'm worried about (the largest one!) is a bit more elusive. However I know the rock he lives in and it's a small one. I've been trying to lure him out at night with food and grab him with the tweezers, no luck so far. Worse comes to worse, I'll pull the rock get him.

[nofilter]

i had a hitchhiker crab in my 100 gallon. i could never catch him, usually just saw 1 big claw reach out and grab stuff (like brine floating by). he lived a 24 lb piece of soloman island rock that i was not about to break up just to get him out. funny thing was, every time i added fish, after about 2-3 weeks, they would disappear. ESPECIALLY if they hung out near this rock. i eventually got him out when i broke down the tank, sold it, left my live rock sitting in tubs unheated, unlighted except for natural light, no flow, and no top-off water for 3 months (ii moved and it took me awhile to get a new setup. low and behold, when i was pulling rock out of the tubs to stock my new tank, i found a crab 3 in. across dead in the bottom. i checked the salinity, just curious, it was way over 1.030. but i had several blue-legged hermits that survived the ordeal. also the temp. was about 60 degrees! i think he starved to death, but the temp/salinity probably drove him out of the rock to look for better conditions.

i have heard you can put some shrimp, the kind you buy to eat, uncooked, of course, in a glass mayonaise jar near the rock, and the oportunistic scavenger will climb in to get it, but cannot climb out.
good luck, let us know how you do it.

[blouden]

Well, I think I finally figured out what my hitchhiker crab is.

It is a Pelia Mutica from the Caribbean (which makes sense on my FL live rock).

I searched through hundreds of sites and this is the closest to my hitchhiker. Although mine's legs are much hairy-er. Here is a pic I found. Mine is about 2 CM across now; was 1 CM across when I first saw it 3 months ago.

[Winged Ocean]

I had florida rock and it was filled with hairy crabs. It took me about 6 months to FINALLY rid my tank of them. I used a utensil that is used to eat lobster with and I speared alot of them. The rest I would run out of thier holes and would squish them with my finger. Sounds gross and mean, but they provided a meal for my hermits and snails that they just loved. I think now with all the crabs gone, they wonder where their crab meal is. I found the crabs to be very destructive to my rock. Before I wiped the population out, they had bore many holes through my rock. Didn't like to see my rock being turned to dust.

[KAS]

I had a few hitchhiker crabs that I also wanted to get rid. It turned out to be pretty simple for me. I just put a piece of salmon (fresh) in the bottom of a mayonaise jar and leaned in against the rock after the lights went out, near where the crab hides. The next morning, I had a crab in the jar. I did this for several nights moving the jar araound, until all the crabs were caught.

Hope this helps.

[dc]

Here's another link of crabs. I caught mine with a flower vase. Propped it up against the rocks with crab bites in the bottom. Checked the vase often when the lights went out. Caught him in 15 minutes the second day.

crabs (http://www.nhm.org/guana/bvi-invt/bvi-surv/crab-tit.htm)

[yaktop]

so I take it if I just stick a cork in the hole of this long hole in the rock he will just eat threw it? guess I'll try the jar thing. thx for the idea.

[blouden]

It works!

I tried the jar thing with a 5" high glass and weighted down a pc. of steamed shrimp with a rock. [Yes, my crabs and inverts eat better than I do.]

I caught the crab by the next morning! DUH, it was too simple.

Attached is a picture of "my" crab. I initially thought it was a Pelia Mutica (http://www.nhm.org/guana/bvi-invt/bvi-surv/images/crab-i02/47x24.htm) , but now think it is closer to one or these two below links -- both of these crabs are un-identified, so I'll stick with "Hairy monster" as my common name.

Pilumnid Family (http://www.nhm.org/guana/bvi-invt/bvi-surv/images/crab-i06/pilumnid/02038.htm)

Xanthidae Family (http://www.nhm.org/guana/bvi-invt/bvi-surv/images/crab-i06/41x06.htm)

http://www.billlouden.com/louden/reef/hairy crab.jpg

[NostiGirl]

OK, here is my soon to be very unpopular .02. I love the little critters in my tank. They fascinate me more than the fish at times. I have a little crab that I believe is the same one pictured above and I love the little guy, all he does is hide and I can coax him out with a silverside but he is very timid. I would never want anything to happen to my fishes but ALL of my fish could whoop this guy's *****. He's only about the size of my pinkie nail. Yes he will grow but I will deal with that when the time comes. I don't have any expensive fish to lose and at this point he is no threat. I wouldn't just kill a living creature that is part of the biodiversity of my tank until given a reason. Yes, I may have to learn the hard way but for now, he is my favorite tank inhabitant.

If worse comes to worse, I have an emerald crab that is about 3" across (not counting claw-span) I can just send him in to "take care of him" :lol: I don't have the "OMIGOD it's a crab, get rid of him!!" attitude at this point.

[FatherDougal]

I have two little crabs that hitch-hiked their way into my new tank but I wasn't really planning on doing anything about them.

Mine are both less than an inch across (including legs), a pale sandy color, and only appear at night to trundle around half-buried in the sand (they never venture onto the rocks)

They seem to feed exclusively on detritus in the top layer of sand so I was just looking at them as good stirrers of my DSB.

Do I really have anything to fear from these little guys? :confused:

[forbze16]

Does anyone know the name of the crab that looks like Darth Maul? This particular crab has either a dark blue or black top half of his shell and and a white/cream bottom half, 2 mean looking a claws and bright red beady eyes?

Found 2 on some of WFForbes's LR, now it lives in my sump.

The links above didn't work for me so I thought I would ask.

Thanks,

Forbze

[blouden]

Well, my crab pictured above is 4 cm across (1.5") and can crush coral rock with his little 5 mm claws. It has eaten several of my crabs and fish from damsels to a copperband buterfly which it caught by its nose.

My crab was the size of a pinky nail (1 cm) when I first saw it less than 5 months ago; but I am sure it didn't grow that fast simply by crushing holes through my live rock. I now have my "hairy monster" in its own 10 gal. tank as I am interested in actually identifying it.

I have found several other hitchhikers (crabs and otherwise) including a few species of porcelain crab, another crab of some Mithrax variety (which may be akin to the Emerald crab). These other hitchkikers are still in my main tank and while I am watchful, they have not alarmed me like my crab above.