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FAQs about Sally Lightfoot Crabs

Related Articles: Crabs, Arrow Crabs, Hermit Crabs,

Related FAQs: Marine Crabs 1, Marine Crabs 2, Marine Crabs 3, Marine Crabs 4, By Species/Group: Arrow Crabs, Emerald Green Crabs, Decorator Crabs/Sponge Crabs, Fiddler Crabs, Pom Pom Crabs, & FAQs on: Marine Crab Identification, Crab Behavior, Marine Crab Selection, Marine Crab Compatibility, Marine Crab Systems, Marine Crab Feeding, Marine Crab Reproduction, Marine Crab Disease, Emerald Green, Mithrax/Mithraculus Crabs, Micro-Crustaceans, Amphipods, Copepods, Mysids, Hermit Crabs, Shrimps, Cleaner Shrimps, Banded Coral Shrimp, Mantis Shrimp, Anemone Eating Shrimp, Crustacean Identification, Crustacean Selection, Crustacean Behavior, Crustacean Compatibility, Crustacean Systems, Crustacean Feeding, Crustacean Disease, Crustacean Reproduction,

Coral Banded Shrimp with Sally Lightfoot 10/19/10
I have a 25 gallon FOWLR tank. I have a coral banded shrimp in there but wondered if I could add a sally lightfoot crab or will one kill the other?
Thanks
<I assume by "Sally Lightfoot" you actually mean a Flat Crab, Percnon gibbesi. Yes, these can get along with Coral Banded Shrimps, and a good friend of mine has had a specimen alongside a Banded Shrimp and a Blood Shrimp for several years. But with that said, her tank is about twice the size of yours, and as you probably realise Coral Banded Shrimps are very territorial. Conversely, Percnon gibbesi is an opportunist that can, will eat anything it can catch, and moulting shrimp that can't find a suitable hiding place will be on the menu. So while it's a do-able combination, it's not a risk-free one, nor a sensible one for a small aquarium. Cheers, Neale.>

Sally light foot, and Stenopid comp. 7/12/10
Hello,
I'm back with more reef questions...
I have a 180 gallon tank (empty but with water/rock) and I was wondering if a mated pair of coral banded shrimp and 1 sally light foot crab would be okay together.
<If they don't get too hungry>
Except for a fair amount of snails
<They may eat these>
as the only other invertebrates, these guys would be pretty much the only inverts in the tank. Fish-wise, there would be a school of green Chromis', 1 Pseudochromis, a Sixline wrasse, a algae blenny and 3-4 PJ cardinals.
Would this overall combination work, again a 180 tank [6'x2'x2'], or should I expect WWIII between one or more things in the tank?
Thanks in advance,
Tristan
<See WWM re crab and boxer shrimp compatibility. B>
Sally Light Foot/Sally Light Foot Compatibility/Crab Compatibility, James' go 7/12/10
Hello,
<Hi Tristan>
I'm back with more reef questions...
<OK>
I have a 180 gallon tank (empty but with water/rock) and I was wondering if a mated pair of Coral Banded Shrimp and 1 Sally Light Foot crab would be okay together.
<I would not chance. When large, they are capable of catching and eating shrimp and other invertebrates.>
Except for a fair amount of snails as the only other invertebrates, these guys would be pretty much the only inverts in the tank. Fish-wise, there would be a school of Green Chromis', 1 Pseudochromis, a Sixline Wrasse, a algae blenny and 3-4 PJ cardinals. Would this overall combination work, again a 180 tank [6'x2'x2'], or should I expect WWIII between one or more things in the tank?
<Looks like a peaceful clan. The Sailfin/Algae Blenny (Salarias fasciatus) does better in aged systems where some algae is present. If not, supplemental algae feedings will be required. May want to read here. http://www.wetwebmedia.com/algaeblensart.htm>
Thanks in advance,
<You're welcome. James (Salty Dog)>
Tristan
Re Sally Lightfoot... now Mithraculus Compatibility/Crab Compatibility 7/12/10 - 7-14-10

Hmmm...(thinking about your reply)
Both you and Bob said that the two would not get along, I didn't expect that they would, I was just crossing my fingers and thought I should ask, hoping the tank may be big enough. Would a handful of Emerald Crabs be okay
with the Coral Banded Shrimp?
<Generally safe, but they are an opportunistic feeder, and if food is not available to them, they may turn to supplementing their diet with corals or invertebrates.>
Otherwise what non-hermit invert would work; helping to keep the bits of macroalgae growing in check? I'm a bit reluctant to put in a urchin because I don't want it to knock stuff over and I would like to keep as much of my
coralline algae as possible. I'm at a bit of a loss as to what could work.
<The Blue Tuxedo Urchin (Mespilia globulus> would be one, as they are much more forgiving in terms of rearranging your rockwork. You may want to read here and related links in the header for methods of controlling algae.
http://www.wetwebmedia.com/algaeconMar.htm. James (Salty Dog)>
Tristan

I.D. For Strange Hitch-Hiking Crab Or Spider -- 01/17/09
Hi,
<<Hello>>
Thank you for your great site.
<<Quite welcome>>
I work at a LFS here in Hawaii,
<<Neat!>>
but have only been keeping salt water tanks for about a year and 1/2. Recently this 8 legged crab/spider (?) showed up.
<<I think I've seen these in the rocks along the shoreline around Kona on the Big Island. It looks to be Percnon gibbesi, the Nimble Spray Crab (see here, down the page a little more than half: http://www.wetwebmedia.com/marine/inverts/arthropoda/crabs/swcrabs.htm ). And while not the true Sally Lightfoot Crab (Grapsus grapsus), it is often seen/sold in the hobby under this common name>>
His legs are banded with yellow and the body looks to be almost clear except for some fluorescent greenish-blue markings. The legs are 3 times as long as the body. From what I can tell he mainly stays on one live rock I have and probably came in on it.
<<Probably>>
I picked most of these rocks from near the shore here.
<<Mmm'¦ I didn't think it was legal to collect live rock in Hawai'i. Last I knew, one could only gather 'dry' rock from above the high-tide line, and then only take what a 5gal bucket will hold, per day>>
I looked all over your sight and also tried some other sites. I thought he might be a sea spider but he is about 2 inches in diameter already, I didn't get the impression from your site that they grew that big.
<<Correct>>
When I first noticed him, he was only about 3/4 of an inch. (He seems to mind his own business but once in a while when another one of the inhabitants gets close to him he does seem to move aggressively towards them.) Hope the pictures come through.
<<They did>>
Thanks for any help.
<<Happy to share>>
I often peruse your site for helpful answers to the questions the customers ask.
<<Excellent>>
Any I.D. or info would help.
Mary
<<Take a look at the link and see what you think. Regards, EricR>>

I.D. of Crab -- 01/17/09
Hi WWM Crew,
<<Hey Mary>>
I just sent you an email a few minutes ago and was checking your website and I believe I found the crab.
<<Ah yes, I believe I just responded to that query>>
It looks like the image of Percnon planissimum (Flat Rock Crab) you have pictured.
<<Hmm'¦ I still think it looks more like Percnon gibbesi in the photo just above P. planissimum (compare the markings on the legs/carapace with those in your photo)>>
Could you tell me about them?
<<Opportunistic omnivores'¦ Large specimens can be a threat to small fishes>>
I have a FOWLER tank that contains a small coral beauty dwarf angel, a small raccoon butterfly, a bicolor blenny and a scooter blenny (also a Lysmata amboinensis cleaner shrimp). Anyway, is this Flat Rock Crab alright to keep,
<<I wouldn't (not a big fan of most crabs for their too opportunistic nature), but that is up to you>>
he is extremely quick.
<<It is probably not a big threat right now to anything listed here other than maybe the shrimp. But that will likely change as it gets larger. Some of the literature on the NET lists these as fairly small species (4cm), but I could swear I've seen them around the Big Island with carapaces that would measure two or three inches across>>
He seems to be getting plenty to eat and has probably doubled in size since I first noticed him 2 months ago.
<<Do keep an eye on this>>
Thanks again.
Mary
<<Cheers, EricR>>

Re: I.D. of Crab -- 1/19/09
Hi Eric R,
<<Hiya Mary>>
Thanks for your reply.
<<Quite welcome'¦hope it was helpful>>
Yes I agree with you it does look like Percnon gibbesi.
<<Ah!>>
And I think I will remove him the next time I do a major water change; which will be soon because there is one other boxy crab with black pinchers I want out.
<<Indeed'¦ Fascinating creatures, but'¦>>
Yes, most of the rock I collected one piece at a time over a one and 1/2 year stretch. Mostly in the upper tidal area around the shore line. I try not to pick up any that have anything alive on them. And even though the pieces have begun to dry out, sometimes after curing there is still live stuff deep in the rock. The owner of the LFS had a permit to make his own live rock from crushed coral and cement.
<<Even this requires a permit? Amazing'¦>>
So early on I seeded my aquarium and the rocks I picked up with that and so for all practical purposes it is now live rock. Again thank you for all your help and your advice. Wish me luck in catching that critter-they are fast.
<<Perhaps some bait in a glass jar positioned near the rock'¦good luck!>>
Aloha & mahalo, Mary
<< A hui hou'¦ EricR>>

Sally Lightfoot Crab--Cloned? 1/12/07 Hello gang! <Hi Thomas, Pufferpunk here> I know you all have seen it all. <There's still new stuff every day!> But this is freaking me out. First, I just moved up from a 29 gallon cube to a 72 gallon bow. Very nice and lots of fun. <Larger tanks are more fun, IMO.> All the animals made the move and it's fun to watch them in their new space. (FYI - I have a mated pair of clarkii clowns with host Sebae anemone (which Salty Dog swore would be dead by now.) <He can only go by experience...> 1 yellow tailed damsel, 1 lawnmower blenny, 1 CBS, 2 diamond backed gobies, 4 blue-green chromis, 1 six-lined wrasse and 1 coral beauty angel. Plus the typical clean up crew. Have I over stocked? <Certainly good thing you upgraded!> Mystery no. 1 - Today I looked in the tank and saw my Sally lightfoot crab was belly up under a rock structure. As I contemplated what to do, I looked over and SAW my Sally lightfoot alive and well, eating off the overflow. WHAT? WAIT! I only have one. Ok, so you're thinking - hitchhiker. <Not necessarily...> But from where? Yes, I did buy a lot of new rock for the new tank but it sat in unheated, unlighted salt water for over a month as I got around to cycling it. And the crab is huge. How could it hide all these months? Puzzling. <I just had the same thing happen to me the other day. I found it to be the empty shell tossed off by a growing crab. Otherwise, I'd say it could have survived in the holding tank. Tough crabs.> Mystery no. 2 - My six-lined wrasse and my yellow tailed damsel are getting it on. What's with that? And I really mean it, they are practically living together. And I don't think he'll do right by her. Shocking. <Some fish do make "friends" of sorts. I doubt they are actually pairing up--they certainly won't be breeding anytime soon.> Mystery no. 3 - My emerald crab is "cleaning" my coral beauty angel. The angel just pulls up to him and let's him pick things off. Have you ever heard of this? <Most any crab or smaller fish can be deemed the cleaner of a larger fish.> Love the site! <Thanks! ~PP> Thomas

Sally Lightfoot molting/ legs deformed Hi, I see there is a similar problem that someone has contacted you about, to one I am experiencing now. My Sally molted 5 days ago, and has not been normal since. I have been using iodine in an 8 week-old reef tank. <This system is a bit new for most invertebrates> Have had a happy Sally for about 3 weeks. All of my numbers were fine except for PH, which I have raised and keep checking. <Numbers, values please... what about your alkalinity? Alkaline earth materials (Calcium, Magnesium principally?> My Sally has all of its legs, however some appendages appear to almost seem paralyzed or partially paralyzed, and attempts to use them. It is eating voraciously like normal, however seems more comfy clinging to rocks instead of cleaning the floor of the tank:( as it cannot lay all legs straight out. I occasionally find him on his back (like once a day) when he is unfortunate enough to be distanced from his new home (on the rock). I thought he would die with in the first two days of finding him in this situation, but he seems to right himself on his own and is good when he is attached on his new happy home and not under it. I keep hoping his legs will regain full function and he will be able to splay them out again. I am adding all sorts of trace elements and increasing the calcium as well. <... adding all sorts... One needs to be careful here... There are many more problems to be had with mis-supplementing than not> So, there is another person out here with that problem. I will be in touch as to the results. Julia <Okay... to reiterate (journey again, L.) most such ecdysis problems are a matter of insufficient nutrition, "poor water quality", and/or a shortage or imbalance of alkalinity and biomineral content... I would be reading on WWM... use the search tool, indices... re these aspects of marines. Bob Fenner>

Re: Sally Lightfoot molting/ legs deformed... Pouring stuff in... 11/13/07 Thank you so much. PH was around 7.8 <Too low... this alone could be the problem> Alkalinity (actually high-with API reef kit, it took 14 drops to get to yellow color-so over 12dkH or over 214.8 ppm KH) Calcium a bit low at 360-380 mg/l <Marginal... and Magnesium?> Emerald Crab just molted happily and well <Oh! Perhaps there is something else going on here...> I have been adding Kent elements to 29 gallon tank <Mmm, this could be an issue as well> iodine: 3/4 cap/week Began using: liquid calcium: 1/2 cap/day to raise-while keeping an eye on alkalinity Tech-m: (magnesium): 1 cap/week <Need to test for if you're adding...> Strontium And Molybdenum: 3/4 teaspoon/4 days Nano Reef part A and Part B: 48 drops each/3 days <... I have a concern re the mixing of all this...> I am watching the last part while I am having calcium issues. I feed with phyto feast daily for my corals and pellet food soaked in Garlic Extreme except for every 3rd day I give Formula A frozen blend (clam-Krill-Mussel-gelatin-scallops-shrimp-fish roe-fish-crab-lobster-squid-plankton-marine algae-Spirulina-kelp-romaine lettuce)-also soaked in garlic Extreme. <Yummy! This sounds good> Hope this is thorough enough:) Thank you so much for your help Julia <Read here: http://wetwebmedia.com/suppleme.htm and the linked files above. BobF>

Sally lightfoot found dead 9/21/05 <Adam J here with you tonight.> Just had a question regarding my tank and the death of my sally lightfoot. I have a nano cube 24-gallon reef tank. I have about 18 pounds of live rock, a cleaner shrimp, a yellow watchman goby and a clown fish. <While I don't mean to make light of the loss in your system, with the stocking list you gave me, you may actually be lucky the sally light foot crab is gone, in my experience they become more predatory with age.> I also have a clam and some soft corals. I found my sally lightfoot crab dead today and it seemed to be doing fine. <Are you positive you found the carcass of the animal and not its molting?> I don't know if any of the other inhabitants could have killed him. I am also not sure if I might have a mantis shrimp or something else that hitched a ride in my live coral. Any ideas. Thanks in advance. <Without knowing your water parameters it is hard to say what the crab dies form, but since your other livestock has shown no ill effects, I gather that your water quality is up to par. As far as the mantis, it's a possibility (though there are other animals in your tank, which would make much easier prey than the crab), they are nocturnal so I would watch at night.> Beth <Adam J> Thanks Adam <No problem.> Thanks for the response. Just wanted to let you know my water quality is about as good as you can get. <Glad to hear it.> I am sure it is not the carcass. I have seen my cleaner shrimp molt and it looks nothing like that. I will keep an eye out for something lurking in the rock, but really don't think anything is <Ok, night time would be the best time to watch, but from your description I don't think you have a mantis either.> there. Thanks again. Beth <Anytime, Adam J.>

When In Doubt, Take It Out 09/15/05 Ted, <<Hello Rebecca>> Thanks for all your help and advice to date. I checked the Stomatella snail and it looks like a match thanks! <<You're welcome.>> I've searched all I can on your site (and a few other linked ones) but have not found a definite match for a crab that seems to also be a hitchhiker and after reading your comment that many crabs may be a problem...wondered if you could help (again!) <<I'll try>> Percnon gibbesi, the Nimble Spray Crab. Tropical West Atlantic. Live in reefs, rocky areas. Hide under Urchins and rocks. THIS IS THE NEAREST PICTURE ON YOUR WEBSITE I CAN FIND BUT MINE LOOKS A BIT DARKER BROWN POSSIBLE & I HAVEN'T MANAGED TO SEE IT IN FULL. Initially I thought it was a hermit crab in the rock. It is the same size and shape as our blue legged hermits...(but without the shell) however as it is in the rock, I've only managed partial body sightings. On several hours more staring, it is dark brown, with paler bands down all legs. The nippers are, pale/flesh coloured and small (it seems to be all legs with pointed claw-like fine ends like the hermits) and it seems to be an algae grazer. I'd estimate it at no more than an inch in diameter. We bought hermits and also a large decorator crab, but this one is definitely not one we bargained for! It seems to stay in the same area. I don't know whether my description is detailed enough so should I try and catch it? How would I go about that? I hope it doesn't end up having red eyes like some of those I've seen on your website. There are some monsters aren't there.<<Identification of a crab can be difficult. I would move the crab to where it can't hurt fish or corals and observe it.>> Thanks again for all your help to.. I hope you get paid a lot for all your wisdom! Rebecca <<You're welcome. I'll talk to our Union Rep about a merit pay increase. Good luck- Ted>>

About Sally Lightfoot crabs and La Bomba 9/29/03 I have been trying to find out some info on the Sally Light Foot. I was told that the two that I bought were male/female and that they do a mating dance. Which I believe that I have seen. If in fact that is what they are doing then how can you tell if they have mated and reproduced? Also is there any kind of care needed for the babies? Thank you for your time. <I am frankly doubtful that you could have been sold a sexed pair as these crabs do not exhibit any pair bonding or conspicuous dimorphism. They are rather territorial though... and I suspect the dances you have seen are skirmishes. As to rearing... larval development in crabs has proven to be very difficult for aquarists to navigate. There is no data reported on rearing Percnon species that I am aware of again. If you have an interest in spawning and rearing crustaceans... let me suggest you pursue the attractive ornamental Lysmata shrimp... there is even an inexpensive how-to book on the subject by April Kirkendall (How to Train and Raise Peppermint shrimp". Best regards, Anthony>

Sally Lightfoot growth. >Hello guys, >>And gal here, Marina today. >Thank you for all your wonderful information you have available, but I could not find anything that tells me about Sally lightfoot growth. How big to they get, and is it normal for my little guy to molt twice in 2 weeks? >>Only if they're doing *exceptionally* well. If yours is molting this frequently, then clearly you're doing something *very* right. As far as how big, let's see if I can find some links for you. Mine only got to be about 4" from tip to tip. However, she never did molt as frequently as yours is. >He seems to be doing fine, when I can find him and is active, and eating constantly. Bill >> http://saltaquarium.about.com/library/weekly/aa100600.htm http://www.wetwebmedia.com/marine/inverts/arthropoda/crabs/swcrabfaqs2.htm http://www.wetwebmedia.com/marine/inverts/arthropoda/crabs/swcrabfaqs.htm >>Well, Bill, in large part because there are more than one species of crab called "Sally Lightfoot", I can't tell you how big this thing will get. I'll just warn you to watch it closely. Marina

Sally lightfoot molted and is now deformed >My sally lightfoot crab was doing fine, but it molted last night. Now he is missing two of his left legs and one of his some of his legs are deformed and bent backwards and his claws look very much smaller and deformed as well. what happened??? he was normal before. Will he grow the missing legs back, will the deformed legs 'straighten out?' >>Wow, I've never experienced this before, but I have to wonder if it could be related to insufficient (available) calcium and/or iodine levels. At this point, I couldn't tell you whether or not the crab will re-molt to its old, healthy self. I am unable to readily find similar stories, let alone any information that would give us an answer. I suggest posing this question to our forums at http://www.wetwebfotos.com/talk. >Also, do decorator crabs molt? >>All crustaceans (nay, all animals possessing an exoskeleton) must molt to grow. Best of luck to you and your poor crab! Marina

Problems Shedding, Crab Hi, How are you today? <Very well. Just got DSL and I am flying about at high speed.> I have a quick question.....I have a Sally Lightfoot that seems to have completely shed, but she lost two of her legs. Is this normal, and will she be okay? <Normal to shed, but not normal to loose appendages in the process. They will grow back, but maybe a sign of a lack in certain necessary elements; calcium, carbonate, iodine, etc.> Thank you for any info. you may have. Marci <Test for what you can and take any corrective measures needed. A good water change is the easiest way of fixing any potential water chemistry imbalances. -Steven Pro>

Sally Lightfoot Crabs Dear Bob: I too love your book and your site. It is very helpful for this relative newcomer. <Glad to hear it.> I have a modest 30 gallon reef tank running for 15 months. The inhabitants are limited: 1 true Percula clown, 1 Pseudochromis, 1 bubble coral, 1 carpet anemone, 40 lbs of live rock, and a clean-up crew - various snails and hermit crabs. Everyone seems fine. I fear I have made trouble for myself by mistakenly adding 3 sally lightfoot crabs today. I now realize that I should have only bought one according to what I have read. Since I bought them mail order, I have no return option. I can't see other local options. What is the likely outcome of keeping all 3? No trouble yet. <Your worst case scenario is one killing and eating the others. I would look into joining a local marine society. The education one can receive is great, but you have the added benefit of other hobbyists with other tanks to take a creature off of your hands or for trading. Thanks, John Rowley <You are welcome. -Steven Pro>

Crab eating my Sally? Greetings. I have a strange fear: <so do I... but I really don't believe that Tony Bennett Imitators are out to get me... I think?!> I have just noticed a small crab in my tank that might be responsible for my recent large Sally Lightfoot disappearances. <hmmm.... it's more likely that Tony Bennett killed your crab> This crab, whitish/grey in color is significantly smaller than either of my Sallies. One Sally went missing about one week ago, but I did NOT notice an ammonia spike and I attributed it to chance. I didn't worry until I noticed my second very large sally dead tonight with this crab within about 1 inch of it under a rock. <Ahhh... an assassin sent by Tony Bennett> He was not eating the Sally, but it makes me wonder. <sure... a dead corpse in ones lair is pretty indicative> Also of note is that my skunk shrimp's antennae are getting quite short (about 1 inch long), <nervous tension... like nail biting> and there seem to be more and more empty shells (from snails or blue-legged hermit crabs?). <OK... in all seriousness, most crabs are opportunistic omnivores if not outright predators. Some behave for months but most will show their true colors in a year or two. Now or later... that crab needs to come out> Oh yeah, my tank: 90 gal, live rock, one regal tang, one Sailfin tang, one maroon clown. Assorted turbo snails, blue-legged crabs, red-legged crabs, sand sifting star, and the remains of two big sally Lightfoots. <yummy... crab legs. Wait while I go look for a tiny bib and a thimble full of butter> I have recently been putting in sea grape for my LFS for my tangs. I inspect the sea grape carefully for anything unusual, and then put it in my tank. The LFS keeps the sea grape in the same tank as its live rock it is curing. <wow is that dumb... a good way to wipe out their stock of Caulerpa or simply just give you a disease to take home for your fishes with the frequent turnover of fresh imports> I have noticed these same crabs on the live rock. The owners kill these crabs instantly when they notice them. <remind me not to panhandle in their parking lot> They are not mantis shrimp, they look more like an emerald crab. The LFS says that they will eat corals, and generally do no good. <they are simply omnivorous just like your sally lightfoot and a Mithrax. All are a potential risk in the long run. Tell him to keep the crabs for large fish tanks... they are great scavengers... or at least feed them to a fish> I am not positive that this hitchhiker got in on the sea grape, but it seems most reasonable. Also I have had these Sallies for 5-6 months with no problems. <OK> The lesson learned of course is NEVER put ANYTHING straight in the tank. <BINGO> I knew this, but the LFS always claims they never have any problems . . . <Your LFS is pretty confident about a lot of stuff... remind me to send Arafat a memo to call your LFS> I religiously quarantine fish . . . I keep learning things the hard way. <alas... too many of us learn this way. Still, I'm grateful you do :)> Anyway: what is this nasty crab? How can I best rid my tank of him? Is this all just a huge coincidence? Thanks, John Michael Woodward <John... a tidbit we wrote on trapping crabs from our upcoming book on Reef Invertebrates:

Lightfoot, light some legs I have a sally lightfoot crab and he/she has lost 4 legs in three days, also all 4 legs fell off on one side. I have two emerald crabs, 1 three striped damsel, three blue damsels, 1 clown, hermit crabs, snails, . do I have the right fish combo or is my crab sick. please help!!! < Yikes... very unlikely that the legs have "just" fallen off. More likely pulled off... I'd guess by the other crabs (real: emeralds, and false: hermits)... or a more remote possibility that the animal has an internal problem (e.g. an infectious or parasitic disease). In any case, the prognosis is bleak to bleakest if you do nothing... if you can't move the Sally Lightfoot, do place it in a separate chemically inert container (outside power filter box?, plastic breeding net-trap?...) away from your other crustaceans... Bob Fenner>

Sally light foot Hey Bob I have a Sally light foot crab. Constantly busy eating algae etc. Also constantly shedding it's exo and growing. JUST HOW BIG IS THAT THING GONNA GET? It is already more than 9" from one leg tip to another. Do I have any thing to worry about its size and becoming a clumsy nuisance? I really like him or her, well it anyway. Kevin Johnson <Wowzah! this is a very large Sally Lightfoot Crab (Grapsus grapsus)... the biggest one I know of was (collected with difficulty in the wild) about ten centimeters/4" across its carapace (upper shell)... This is a very big crab for a reef tank... and though they mainly eat algae, this species has been recorded eating invertebrates... even capturing small land mammals... Bob Fenner>

Re: Sally light foot I am sorry I must have said it wrong. The crab is about 9" from the very tip end of one leg across to the very tip end of another. The body of it is about 1.25" across. Is it going to get much bigger. I don't want it eating my invertebrates. Right now it is very content on eating algae. Do I need to take this one to a pet store soon? Kevin Johnson <I understood the end to end part... those are some long legs! And I wouldn't trade this crab in if it was doing a good job, and leaving your other livestock alone. Bob Fenner>

Percnon gibbesi Hi Bob - I recently walked into the LFS and, as described in your chapter on crustaceans, scurrying around inside a display tank were a half dozen Percnon gibbesi with an accompanying "Sally Lightfoot Crabs" I.D. sign. The Nimbles really do deserve their correct common name and fascinated ... I bought one. Nimble Sally has been in QT for two weeks and I'm getting ready to move it into my display. The only behavior that I've found curious has been the specimen rubbing its legs together; occasionally "wiping" it's face with legs or claws; and rubbing / "scratching" its back on the piece of rock I keep in non-fish QT. Are these unusual habits for Ms. Nimble? <Not at all... general cleaning> Recently, I found a discarded exoskeleton ... does the itchy behavior precede a molting event? <Perhaps ecdysis (fancy schmancy term) is related... but maybe not> Should the abandoned shell be regarded as a decay/ammonia threat and removed from the tank? <I'd leave in for a few days... little ammonia/protein in it... and like many crustaceans your Percnon may consume it for mineral et al. content to build new exoskeleton> Finally, should crabs receive the "freshwater dip" treatment prescribed for fish? <Not most, and not this one> Thanks for your help - Tom <Thank you for your input and asking. Bob Fenner>

Blue Linckia and catching evil Sally Lt foot? Hi Bob aka Lorenzo, Bob knows about my tank, but you seem like a nice knowledgeable guy so here goes. I would like to catch a nasty Sally light foot (my sister's name, I should have known :-)). Anyway it ate an otherwise healthy (but teeny- 1") False Perc. I am thinking I will replace with Clarkiis, but that's another story. <This does happen... Bob as Bob> Anyway he (or she) looks impossible to catch, so how do I do it? I looked on the FAQ and couldn't find anything. <You might be fortunate to bait this faster than lightning crustacean out with a meaty item tied to a stout thread or bit of fishing line... and net it out from there> Also looked on the FAQ, as if I catch the darn thing I am thinking about a Linckia star. The question I have is how established is my tank? Or would I need more time? About my system I have had it going since December. It is a forty gal breeder with 40 lbs or so of LR and 40 lbs sand (some live). Usual perimeters are: Temp 78-80 pH 8.2 Ammonia, Nitrites 0 nitrates under 10 Alk 3-4 Ca 390-450 Phos .1-.2 I use an Ecosystem 40 and have 144 watts PC. I have a MaxiJet 1000 for circulation. All creatures are doing well and include: Midas blenny, juvenile Sailfin tang (who is not long for the tank at his/her eating rate), a Common Cleaner, some Turbos, a regular mushroom, and a Rhodactis. No deaths or anything for months except the ill-fated clowns (one jumped out -- maybe spooked by Tang and the other was eaten :-o). I won't put any slow creature in until the SLF is out, but aside from that what do you think? <Would skip a Linckia for this small system... Look for a smaller Fromia Seastar species in its stead. Bob Fenner> --Jane J

Cleaners The cleaner shrimp are doing fine. However, when I got home yesterday, my smallest sally lightfoot crab was decimated at the bottom of the tank, missing several legs. Is it likely the Lysmatas are the culprits? From reading about these shrimp on the site, my guess would be that they got hungry and decided to snack on the crab. <Very unlikely... crustaceans know who to avoid... and Lysmatas are pathetically slow compared to this genus of crabs... You may have a Stomatopod... Alpheid... hungrier fish... or just a sick/dead Sally...> Hope you're doing well--got your book on Monday and it's been a great reference--very informational and easy to read. Thanks for your contributions--and for the section describing the terrible use of cyanide to collect fishes. I'll certainly ask about the origin of every specimen I buy in the future. <Ahh, deeply gratifying. Thank you. Bob Fenner> Talk again soon! James A. Deets

Lightfoots OK--now you'll really know what a greenhorn I am. When I got home this evening, I pulled another "dead" sally lightfoot crab out of the bottom of the tank. Before I ran a barrage of water tests, however, I counted them--and there were three crabs on the rocks--and we started with three. Now I know what an empty exoskeleton looks like after a crab molts. I guess they're happy and growing. . . <No worries... glad to read, know... and do leave these cast off exoskeletons in the tank for a week or two... sometimes consumed, incorporated by the shedding animals to augment their new ones> On another note--I guess I need to build a calcium reactor, and soon. Tonight I dosed the aquarium with the Tropic Marin Bio-Calcium. It's a powder product, if you're not familiar with it, and the instructions say to just put the powder in the tank by sprinkling it on top of the water. <Very familiar with the product and company... both are excellent> The hammer coral, moon coral and finger leather were unaffected--in fact, all three of them seemed to love the Ca boost and extended their polyps even further. The moon extended its tentacles about an inch, and some of the hammer polyps were an inch long as well. However, the pagoda got what looked like "blisters" all over it and the flesh looked very irritated, and the bubble and Goniopora (I know--bad choice. . .), and toadstool leather all retracted completely. Is a sudden increase in Ca likely to cause such a reaction in these species? <Yes... a few things at play here... like you state, sudden increase in calcium, but also pH (locally), and physical irritation (irrespective of how well the product appears to dissolve... Best to pre-dissolve, introduce the new material by way of a filter, sump... and slowly (perhaps rig up a drip bottle or siphon of airline tubing...> (Based on the label instructions, Ca was increased roughly 35 ppm by the dose.) Any permanent damage? <Not likely, unless the animals health was impugned before use... but more nicks toward the negative...> (They all seem okay now, after several hours--but no reason to put them through any stress if I can dose the Ca gradually, on a daily basis, and by first dissolving the Ca in the top-off water--or better yet, by building a reactor.) <Ah yes... the process continues.> Thanks once again for your thoughts. <You're welcome my friend. Bob Fenner>

Legless Lightfoot One of my Sally Lightfoot crabs molted yesterday. However, today he is missing one front claw and two of his legs on the right side. Is it common for these crabs to lose legs in connection with a molt? Or is something amiss here? <Hmm, sometimes in ecdysis/molting some limbs are not formed due to nutritional reasons... perhaps other factors... but in most cases like this, "someone" was munching the inopportune animal during the "hiding phase" of rehardening its new exoskeleton... it can/will "re-make" these lost limbs next molt...> In case you don't recall, one night I saw a different crab in the tank that must have come in on the LR. The damaged lightfoot is now "guarding" a hole in the LR, and I can see the two front claws of the "mystery crab" at the entrance to the hole. Occasionally the lightfoot will "pick" at the other crab's claws. Are there any species of crabs that eat other crabs? <Many> This "mystery crab" was pretty small before, but is it possible that as he's getting bigger he's munching on the Lightfoots? Or is this loss of legs just something that sometimes happens when they molt? <More likely the former. Bob Fenner>

Question regarding Mithrax and Sally Lightfoot Crabs It appears that either a newly added Mithrax or Sally Lightfoot Crab killed two of the shrimp in my 60 gallon tank. My guess is the Mithrax but I would appreciate your opinion. <Yes, this does happen with both crab species... they are not "simple herbivores"... not nearly as opportunistic as some crab species... but still...> Also is there a way to catch the offending crab without dismantling the tank. <You can try baiting, trapping... per "crustacean" removal sections on our site: www.WetWebMedia.com> Thanks for your input. Mark Hill <Good hunting my friend. Bob Fenner>

Lightfoot Crab Just a quick update--the sally lightfoot crab that lost a claw and two right legs molted today and has all his legs back! (Hmm, as I had told you... neat trick eh?) I had been offering him frozen krill on the end of a skewer every other day or so since the "accident" to ensure he was getting plenty to eat and to speed up the growth/molting process. Looks like everything is going to be fine on that front! (Ah good) I also caught a glimpse of the peppermint shrimp last weekend--he's been hiding out in the back of the tank, apparently, and has not become a lightfoot meal, yet. (Also good news) The new tank is on order. I'm building the sump/refugium (30 gal) this weekend. Everything else has been ordered or has already arrived. I'm sure I'll have a question or two once this whole process really starts cooking, but I've also found a newsgroup with some pretty experienced reef keepers who have been very helpful as well. (Ahh!) Take care. Chat again soon. --James D (Bob Fenner, in Cabo San Lucas)

Crab eating fish Dear Mr. Fenner, First, thank you so much for the time and information you offer fish hobbyists. Your book, Conscientious Marine Aquarist, has been a major asset. <Ah, thank you for your kind, encouraging words> I have had a 29 gallon saltwater tank since January of 2000. The first 2 residents were a sally lightfoot crab, and a pygmy angelfish, Centropyge argi. Both are still doing well. About 7 months ago, I added a Swiss guard Basslet, and have been very pleased with this fish as well....until today. <Oh oh> When I arrived home from work, I found the crab eating the Swiss guard. I can't say for certain that the crab killed the Basslet, only that he made a meal of him. <You are right about the likely course of events> The crab is now approximately 4 inches across, leg to leg. Last November, I had a Gramma disappear from the tank, and at the time blamed it on the now-departed mantis. <Possible... Grammas are also great jumpers> My question is this: Will a sally lightfoot kill a fish if it is able to, and/or once it has eaten a fish, are any other small fish safe? <Yes, this species, especially when large can/will capture and consume fishes> I don't want to blame the crab unfairly-- I actually like the crab-- but am not willing to sacrifice fish to it either. <You may have to settle on just the inhabitants you have now... or look to getting a larger system with wary and aware larger fish species... Bob Fenner> Again, thank you. Sincerely, Owen Smith

Sally Light Foot? Hi Bob. I was reading about the Percnon gibbesi, the Nimble Spray Crab on your site. Is this crab also known as the Sally Light Foot crab? <Mmm, maybe... perhaps sold, labeled as this by some... though the "real" Sally Lightfoot Crab is Grapsus grapsus> Does it need to be able to get out of the water periodically? <Yes> Any further tips on keeping this crab healthy? <Do use your search engines here. Not much that is practical/husbandry known about these crabs. Bob Fenner> Gracias. Zimmy

Sally Lightfoots? Hello once again mi amigos- <Buenos noches> Do Sally Light foots eat coral? <Percnon gibbesi? Not usually... but do cause some damage, closing by walking over them> A salesman stopped me from buying one for my reef tank. He said that they eat soft coral. I already have one in the tank, great scavenger and all, and was looking to add a new one. Should I be worried about the one I have? Thanks, Mark <Not worried... but as with almost all crabs, I'd keep an eye on it. Bob Fenner>

Sally eat/lightfoot Hello again! I think I botched up....I added a sally lightfoot crab to my tank the other day. So far so good, but after reading a bit on the net, well, now I'm worried! My tank has mostly half grown damsels and I don't want them eaten!! Do you think if I target feed the crab it will be okay or should I get it out now? I feel like an idiot because I know enough to read up on things before buying them but every once in a while I lose my sanity..... Thanks for your help, Barb <Barb, we all make mistakes, don't worry about it. I think that target feeding of the crab will be a great idea. If your tank is big enough and there is enough food source the crab won't be a problem. It you notice some of the damsels missing then take the crab out. Consider this a lesson and don't worry. You haven't lost anything yet. MikeB>

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