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FAQs about Marine Crab Diseases, Pests, Predators...  

Related Articles: Crabs, Hermit Crabs

Related FAQs: Marine Crabs 1, Marine Crabs 2, Marine Crabs 3Marine Crabs 4, Marine Crab Identification, Crab Behavior, Marine Crab Selection, Marine Crab Compatibility, Marine Crab Systems, Marine Crab Feeding, Marine Crab Reproduction, 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,

Calico Crab refusing food        7/12/15
Hi, first time writing in!
<Ah; welcome>
I recently moved my calico crab (*Hepatus epheliticus*, 4" across the carapace) into a larger tank. Originally she was in a 3 gallon, but the nitrates got out of control fast (the day before the move they were testing off the chart), so I bumped her up to a 25 gallon. The tank is filled with 3 inches of fine aragonite sand
<Mmm; well; the natural habitat of this species is more mud and sand...>
and pre-cycled water from a coral-only tank, and the water levels all check out as optimal as of this morning. She is the only animal in the tank other than a single turbo snail.
Anyway, she's been in this tank for going on five days, and the entire time she's been refusing food. I've tried scallop, shrimp, krill, even a live turbo snail, with no success. When she was in the 3 gallon, she used to burst out of the sand and dance excitedly the moment I put the feeding stick in the water. Now she shoves the food away. Is she just sulking because of the move?
<That and the NO3 exposure... can severely alter physiology... cause blood cells to disrupt...>
I'm concerned she might still be affected by the nitrate spikes in her old tank.
Thanks for any advice you can offer!
<Keep offering some food daily... remove if it's not eaten w/in a half hour or so. Bob Fenner>

Dying Shrimps And Crabs, But Not Snails Or Fish 7/29/10
Hello crew!
<Hi Jennifer>
I have a low light reef that has been up and running for over a year, but recently I've been slowly losing my cleaner shrimp and Emeralds Crabs. It's possible a few hermits have disappeared also but I'm not 100% sure.
My fish, corals and snails are all perfectly fine. I use IO salt kept @ 1.025-1.026, PH is fine and stable, no nitrates or ammonia, weekly water changes with treated and treated tap water, I haven't recently tested calcium, Mag or Alk but there is plenty of healthy coraline algae. The only think I can think of is the animals I'm losing are the type that molt and I don't recall seeing many molts lately. These poor creatures have been in the tank since the beginning and have now been slowly dying for about 3 months. They don't get mangled or eaten in any way, I find them looking sick or already dead. I've tried taking the sick ones out and setting up a separate tank, even trying RO water in the hospital tank instead of the tap water in the display. The only thing the same in both tanks is the salt. Is it possible there isn't enough iodine in IO's salt lately? That seems unlikely to me, but at the same time do you think that makes sense since only the molting animals seem to be dying? I've never seen an iodine test, perhaps it's time to look for one. Any help would be appreciated!
<Two things come to mind. Are the shrimp and crabs getting enough to eat?
And, lack of iodine can cause problems like this as iodine is necessary to ease the molting process. A test kit isn't necessary in my opinion, just follow directions on the iodine/iodide label. Do not depend on the iodine
level in the IO salt, and for that matter, calcium or magnesium as these elements are slowly depleted by the animals/algae that require this. These parameters should be tested regularly and supplemented when necessary.
If your fuel gauge didn't work in your car, would you always know how much fuel you have remaining, or would it be "I think I have enough left".
James (Salty Dog)>

rock crab, comm., hlth    4/4/10
I add I am in charge of caring for life product at our seafood restaurant, 100 gallon saltwater tanks, the tanks hold them rock crab recently they had shed all their smaller legs, all in one night what could be causing this problem we are on the ocean, self enclosed system, importing water directly from the ocean so the problem should not be pH levels or salinity you can look restaurant it is berth 55 fish market and seafood deli, in Long Beach California if you can give me any help with this problem please contact me at XXXX.
thank you
<I suspect there either is/was something wrong with the water... likely metabolite "build-up"... I'd be checking your nitrate in particular, giving whatever mechanical filter media (floss, pads) a rinsing, and switching out any chemical filtrant you use. Bob Fenner>  

Help! Dead Crabs: Sudden Crustacean Death in Newer Tank. Not Likely Caused by Worms. 10/7/2009
<Hi Wayne>
I'm just looking for some advice.
<You've come to the right place.>
I started a salt tank about 12.5 weeks
ago. I was fortunate enough to have a relative in salt water aquariums.
With his help, I was able to get live rock and sand from a tank he had already established. With that, I was able to get my tank to cycle in about 2.5 weeks.
<All good so far.>
At the moment, I thought it would be a smart idea to begin working on biological filtration before I start putting in the good fish. I started with two sally light foots and a big turbo snail. week later got two pieces of live rock with a lot of livestock. Week after that, I got 3 horseshoe crabs, and then got two more pieces of rock along with a sand sifting star.
<The Horseshoe crabs and the sand sifter were not the best choices. They need a lot of live sand to scrounge for food and frequently starve to death:
http://www.wetwebmedia.com/sndsftstrfaqs.htm  >
Satisfied, I figured I would sit back and let the tank mature for about a month or two.
It's been about 2 weeks or so since I have last added any new livestock. At the moment, I was feeding the crabs frozen silver backs/brine shrimp and the live stock on the rock Reef snow, as I'm watching my tank, I have noticed some growth that wasn't on the rocks when bought them a few weeks ago. I figured the water is doing great then.
<Hmm... testing results? Ammonia, nitrite, nitrate pH, SG?>
Lots of feather dusters, polyps, sponges, and some other things I can't identify. While looking at my tank growing, I noticed I had a bristle worm. If I had one, I figured I have more.
<Likely so.>
I started to research and I have read they are not as bad as they seem.
<Normally quite beneficial.>
There are certain worms that kill coral and fish but most just scavenge and reproduce quick. The one I saw was about 2 inches and was purple in color. My guess has been, he came in on one of my rocks and has been there for at least a month, I figured if he wasn't bothering the livestock, I have no need to bother him. Now, to get to the good part. One morning last week, I woke up to one of the sally light foots hanging dead off of the rock where both crabs lived. I checked to see if it was a molt and it wasn't. I figured the two crabs fought and he lost. He had all his limbs and didn't look to be wounded.
<Most likely was not a fight then.>
I pulled him out and put him in the trash. I decided maybe the remanding crab was aggressive and didn't want to get another. So, tonight, I fed the crab some brine shrimp, put some reef snow in, and turned the lights off. About 3 hours later, 10 at night, I turned the lights on to see if I could see if there is any worms on top of the sand. What I saw was the last crab convulsing hanging on his rock with one leg. Looked a distance from where he was hanging and I saw his claws and a leg. It only took about 2 min after I found him he died. I'm not convinced that it was the worm I saw. The star and the little coral I have not been touched. Both crabs don't look like they were sought out for food. My question is, what has been known to do something so violent. I do know it has to be a hitch hiker. I think the only way to know is to catch him.
<Probably not a hitchhiker. Could have been a problem while trying to molt - http://www.wetwebmedia.com/swcrabdisease.htm >
Where should I start first? Building a trap, setting up tape, or checking in on the tank through the night? I have no plans to get anymore rock. I got my fill. What I know is, at this moment, it is not safe to put in any fish.
<Water testing is in order here: check all of your levels
http://www.wetwebmedia.com/marine/maintenance/maintindex.htm Scroll down to Marine Water Testing and read the linked articles.>
50g tall.
204 fluvial filter
power head( don't know how big)
1wht 1ble light.
about 40-50lbs of rock
3 horse shoe crabs
two sally light foot crabs (dead)
sand sifting star
one big turbo snail
a few soft corals (came with live rock)
bristle worm (came with rock)
water change every 2 weeks. 5g.
<Do not see a skimmer listed - have a read here as well:
http://www.wetwebmedia.com/toskimornotfaq.htm >
Thanks for any advice,
<You don't have a worm problem, I think you likely have a water quality and\or you are low on certain critical elements needed for crabs.>
Re: Help! Dead Crabs: Sudden Crustacean Death in Newer Tank. Not Likely Caused by Worms.> 10/12/2009

<Hi Wayne.>
I really do appreciate you helping out. I've only been told to test for the nitrite/nitrate levels. I purchased a full testing kit tonight and tested the waters.
I did not purchase the test kit with strips. doesn't seem to give accurate readings.
<They do not.>
Almost everything came out ok. Calcium was high and so was the Phosphate. Doing some research, there doesn't seem to be any danger with high calcium but the phosphate will harm and kill coral and inverts?
<Not really, but it will encourage algae and Cyanobacteria. Crustaceans need iodine to molt. If your system is deficient in iodine, your crabs can die while molting.>
thanks again

Gecarcinus quadratus Molting and Care 4-2-2008 I have 2 Halloween land crabs <<(Gecarcinus quadratus)?>> I have 2 Halloween crabs and one of them shed last night for the first time and it looks as if all his legs are missing except for his 2 front claws. <<A bad molting; http://www.afsc.noaa.gov/Kodiak/shellfish/cultivation/crabGrow.htm .>> Do his legs eventually grow back in? <<Perhaps with a few successful moltings. What are you feeding? What is the environment? Consider soaking the food in a marine iodine supplement every so often. Read here; http://fireflyforest.net/firefly/2006/05/28/Halloween-crab/  and here http://www.wetwebmedia.com/marine/inverts/arthropoda/crabs/swcrabs.htm  and one more  http://www.wetwebmedia.com/marine/inverts/arthropoda/crustace.htm  >> Thanks, <<Welcome.>> Angie <<Adam J.>>

Scary Shrimp or Killer Crab? <Mystery Losses> 11/15/07 Hello <Hey there! Scott F. in today!> I have been reading your sight for months now and love it. <Glad to hear that! We have some pretty cool folks who work very hard to bring it to you each and every day!> My knowledge has grown in leaps and bounds thanks to you. <Awesome!> I started this tank knowing pretty much nothing about salt water other than I like to surf a lot in it. <My other obsession!> I currently have a 30g reef tank 36#LR 1"ls Prizm nano skimmer (I know not the best equipment but its what I can afford at the moment) Penguin 330 filter The tank has been running for about 7 months now The water levels: Zero ammonia nitrate and nitrites Ph daytime is 8.5 temperature 80 SG 1.026 I do a 5G water change weekly. My livestock: 2 Mexican turbo snails 10-15 blue legged hermit crabs 1 Skunk Cleaner Shrimp 1 Blood Shrimp 1 Ocellaris Clown (tank bred) 1 Cherub Pygmy Angel Coral: Green Star Polyps Pulsing Xenia Yellow Polyps In the past month coralline algae has begun to grow on the glass the LR is almost completely purple as far as I can tell everything is healthy in the tank. <Glad to hear that!> Finally, my question: is I had 2 sally lightfoot crabs 2 months after the tank was started and also had 2 peppermint shrimp to take care of the Aiptasia. The two crabs disappeared over a period of a couple weeks I thought they may be hiding and didn't think anything of it but they are gone-completely disappeared. No trace of the animals at all. A month my peppermints disappeared over a period of time also. <Hmm...could their be a "ram among the sheep?"> I though it might be a mantis shrimp or a pistol that hitchhiked on my rock but I watched the tank quite a bit by night over the past month and have neither seen nor heard any clicking. I was wondering if you could give me any insight as to what could be eating them. <Well, it's hard to say. The disappearance of these animals could be coincidental, but there may be some nocturnal predator out there. I wouldn't totally rule out a Pistol Shrimp, but the lack of telltale clicking could be a sign that this is not the case. I would consider another possibility, like a crab of some sort. Nasty little crabs often come in as hitchhikers on live rock, and remain undetected until the losses mount. Do consider this, and go on a nocturnal safari...You may find the culprit!> Thank you Your sight is amazing <Umm- not really- I need my glasses to read small print...Ohh- the SITE- yeah- it's pretty darned good. Thanks so much for stopping by! Regards, Scott F.>

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>

?Disabled? Mithrax Crab - 08/11/07 Hi guys, hope you are all well and happy! <Thank you> I contacted you a while back and got some wonderful advice from Mich, so, with my new questions I thought I'd come straight to you as I am rather concerned for my Mithrax crab. He/she, (haven't managed to work out which yet), had a molt the night before last. Unfortunately, he, (I'll use the masculine for ease!), managed to leave his main front left limb including claw, behind. I am hoping that this in time will grow back, but have been observing him since this morning and realised that his remaining, rather mean looking clawed limb appears weak and not fully operational. Because of this he does not appear to be able to feed. Poor old "crabby"... sad to say it, I am rather upset as he is quite a character. I managed to hand feed him this morning and this evening but it was rather difficult and I am not sure he has had anywhere enough to sustain him. <Mmmm> Do you have any idea if this weakness is just a passing phase and anything to do with the molt? And whether the missing limb will definitely grow back, and if so, any ideas how long this will take? <I do have such ideas... these occurrences are typically associated with either "something" deficient in the way of water quality (biomineral and/or alkaline content) and/or nutritional deficiency... Please look up these terms (the search tool likely) on WWM and test for Ca, Mg, alkalinity, provide sufficient foods... for your Mithraculus> I appreciate your time as I am sure does "crabby"! Kirsty. <Hotay! Bob Fenner>

Salinity Change kill crab?  8/4/07 I did a 5 gallon water change on my 75 gallon reef tank. It lowered the salinity from 1.022 to 1.020. The next morning I found my sally light foot crab dead. Was it the salinity change? How much is too much of a change for them to handle? (Fish, anemones, clam, scallop, green brittle star, sea urchin, feather duster, mushrooms & coral). Also, I can't get hubby to invest in a chiller. The temp at night is 78, but reaches 84 in the afternoon. Is this too much of a change? Is ice cubes in a bag an ok way to try to keep it under control? Thanks again! Kristie <<Kristie: While many fish stores keep the salinity of their fish tanks down to 1.019, the salinity of the ocean is 1.026. While the fish can tolerate lower salinity, invertebrates can't. For that reason, I recommend that you start increasing your salinity no more than .002 per day until the salinity is at least 1.025. I keep mine tanks a bit lower than 1.026 to compensate for the increase in salinity that will happen with evaporation. If you don't have one, it's much easier to measure salinity with a refractometer. Regarding the temperature, the surface temperature where most of our critters are from is around 82 degrees. Thus, I don't think the swing from 78 to 84 is too much of a change. To give yourself more leeway, you could drop your base temperature down to 77 or 76. While I don't consider 84 too high, I've noticed that higher temperatures are harder on the critters than lower ones. Ice cubes in a bag is a good way to drop the temperature. Another way is to set up a small fan to blow across the water to increase evaporation. Best of luck, Roy>>

Mystery Crab Deaths - 03/25/07 I'm worried about a SW tank b/c of two recent deaths. <<Oh?>> The tank is a 100-gallon reef with 20-gallon fuge/sump with 100-pounds live rock, a yellow tang, Rabbitfish, 2 clowns, 1 peppermint and 2 cleaner shrimp, sand-sifting starfish, assorted LPS and SPS corals, and until recently 2 sally lightfoot and 2 emerald crabs. <<Sounds good...though I'm not a fan of the sand-sifting star (will decimate the biota in the san bed), and the crabs can be a threat to fishes when/as they get large>> Ammonia/nitrate/nitrite:  0, phosphate:  0, calcium:  500 (I know, too high....been that way for 3-months despite turning off the calcium reactor), alkalinity:  11 dKH, SG:  1.025, temperature:  81, pH:  8.2. <<Hmm...do consider new/different brand test kits to validate these numbers...especially your calcium and alkalinity readings>> Nothing new has been added to the tank since the Rabbitfish about six weeks ago.  About 3 months ago, one of the sally lightfoot crabs died.  We checked the water immediately and all was unchanged (numbers listed above), so we attributed it to an incidental event.  Now, one of the emerald crabs has died and we are paranoid that this it is the first warning that something is terribly amiss with the tank! <<Mmm...maybe...maybe not>> Numbers are still unchanged as listed above. <<Do try to validate these>> We do approximately 10% water changes every week (or 2 weeks if we're being bad).  The live rock has algae and tons of pods on it and all the corals get target fed so I don't think lack of food is an issue. <<I see...and one possibility that crossed my mind>> The fish obviously get fed flake as well as Nori sheets every few days. <<A bit more variety would be good....perhaps add some frozen Mysis and New Life Spectrum pelleted food to their diet>> So, my top rule outs for the demise of the crabs:  high calcium, iodine (we do not test for nor add), incidental deaths (please pick this one)!  Oh, by the way, these are definitely the crabs, not just molts.  We removed the specimen and cut it open to make sure (stinky!). <<These deaths may very well be "incidental" as you say.  I find that these crabs rarely do "well" for extended periods in closed systems...often succumbing to either starvation, predation (many times from "other crabs")...or missing/deficient elements of water chemistry.  You say these crab were not "molts," but perhaps their deaths are the result of "failed" molts...possibly due to a deficiency of an essential element (iodine), or maybe even as the result of a genetic abnormality>> The only other abnormality we are aware of is a small growth of Cyanobacteria (2 x 3 inches in 2 spots) on the live rock. <<I don't think this is a factor here>> We have been siphoning it off and trying to get rid of it per the information in the WWM archives.  So far we are 3 days past siphoning with no visual evidence of return. <<Excellent>> Could this be related? <<I believe not>> Thanks for any information and your time! <<I can't say with any certainty what caused the demise of the crabs...but if water quality/chemistry is not the issue, then I think aggression from the other crabs to be a real possibility.  Regards, EricR>>
Re: Mystery Crab Deaths - 03/26/07
Thanks for the reply. <<Quite welcome>> We will purchase new test kits ASAP to validate numbers. <<Excellent!  I consider Seachem of good quality for value>> Just to clarify about our feeding, we do feed a variety of food to the fish....mysis, homemade fish recipes from Mr. Fenner's book, etc. <<Ahh...very good>> Regarding your comments about the starfish, I read conflicting reports on the sand sifting starfish before its purchase. <<Indeed>> Some seemed to say they were great for cleaning the sand bed, others said they were too good in cleaning the sand bed. <<Subjective opinions/evaluations yes...and mine falls in with the latter>> We are in process of setting up a second tank which will be plumbed in-line with the current tank (i.e.:  similar water parameters).  Does it sound reasonable to move the starfish back and forth between the two tanks (with proper acclimation) every six months or so to give the other sand bed time to rejuvenate or would that be too stressful on the star? <<Hmmm, well Michele...every time you relocate the star you risk physical injury and/or introducing air to its vascular system (usually fatal).  The fact the two systems will share plumbing/water may allow one to "seed" the other (though not as efficiently as a purposeful refugium); and is best accomplished without such a voracious sand-bed predator ever being present in the seeding display tank.  If you wish to keep the starfish, I suggest you leave it where it is>> Thanks as always for the advice! <<Always welcome, Eric Russell>>

Crabs and Turbos... on their way out    1/15/07 Hello, <Hi there> I currently have a 24G nano set up at my home. I have several fish(3), some peppermints, a cleaner shrimp, a few small corals, Turbos, hermits and an emerald crab and  anemone crab. The tank has been established for one year (next week). I have had pretty good success with the nano since I started it. I do water changes every 10 days, check the water every other day, have good lighting set on a timer, a chiller to keep it at 76 degrees, live sand, live rock, low algae, good coralline algae....just to give you an overview. My question(s) are: 1. I have a  sudden "die off" of turbo. One every 3 days on average. I find them on their backs in the morning, usually being munched on my the hermits or bumblebees. Could it be random?( has a slew of baby Turbos doing very well) <Mmm, being this/too regular... I don't consider random... something is either amiss with your water quality for these snails, and/or a predator is at play... I suspect the crab/s> 2. My anemone crab (who is fairly new) just molted and lost both is large claws and two legs?? <Again... can be water quality (a lacking, imbalance in biomineral (Ca, Mg) and alkalinity... or a predator at play here> He still has his filter feeders, so he might survive? <Yes> 3. My emerald crab lost a claw about 6 months ago and never regrew it. <Okay... I'd be definitely reading up re the imbalance alluded to above... Here: http://wetwebmedia.com/calcalkmar.htm and the linked files above. It is hard to maintain such consistency in smaller volumes as yours... and over time, the more-easily soluble sources in substrates (gravel, rock) are lost... and become rate-limiting... Can replenish to some extent with water changes, feeding/supplementation, but switching out, adding new substrate is the simplest improvement means> His other claw grew very large, but now he has lost it as well. What are his chances? <Fine if no real predators> They need those claws to eat, correct? <Mmm, no... really the smaller set/pair under/behind the largest, forward-most are/can be used here... the biggest pair are for defense and killing...> Anything I can do for him. <Read, understand biomineral, alkalinity chemistry...> Is there anything that might be causing this to happen to my crabs?? Calcium and iodine levels always look good when I test for them. Thanks, Matt <"Looking good"... is of no use here... need numbers, not subjective evaluations. What is your Magnesium? About 3X the Ca? Alkaline reserve measure? Bob Fenner>

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 <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

- Dead Crabs 8/21/06 - I've had a 20 gallon saltwater tank for several days now, but I can never seem to keep crabs alive. I at one point I had 5 hermits, all dead. Just recently I had a sally lightfoot but like the rest, it started to change colors (pinkish) and died. I guess its my water quality, but my LFS only said to check for ammonia, nitrite, nitrate, SG, and ph (they are all in normal ranges). Do  I also need to test the Ca, Alkalinity? anything else? Also I was told I  wouldn't need a protein skimmer since my tank was only a 20, and that's why I never added or tested chemicals like calcium and iodine. Do I need  one? thanks, Andy <Seems to me that if your tank is only 'several days old' then you need not be concerned at this point about calcium or alkalinity. I would consider your source of saltwater, although with things still cycling and such, I'd really wait until everything is fully settled in a couple of weeks to make any judgments. I'd keep trying on the crabs and perhaps consider some other methods for acclimation. More about that here and the FAQs beyond: http://www.wetwebmedia.com/acclimat.htm Cheers, J -- > Trouble with Crabs 6/2/06 Hi <Hi> I have been holding & feeding some blue swimmer crabs now for about four years. One problem has been consistent, when about 50% of the crabs are entering their molt phase they just die. These are crab caught in the ocean that have been held for about a month. Any ideas? <Having problems molting is a common problem with crustaceans.  Unfortunately some death is natural, although your rate seems high.  I would suggest dosing with Iodine, this helps with molting quite a bit.  Also make sure the crabs are not being attacked by there tankmates right after molting when they are most vulnerable.> <Chris> Angus Cameron

Iodine and crabs 6/3/06 Thanks, how do I dose with iodine, in water or feed, dose rate, what does iodine actually do? <Iodine assists in the molting process, it is added to the water.  Dosing rates vary based on the brand, so follow the directions on the bottle.  It is available through most LFS or on-line.> Regards Angus C. <Chris>

Dead Emerald Crab...Leave In Tank? - 03/22/06 Dear Crew, <<EricR here...>> After several weeks of reduced activity and increased 'hiding' it appears that my Emerald crab has passed.  I have located him in a tiny pocket underneath lots of live rock with my flashlight. <<Ok>> His shell has turned a creamy white and it has not moved at all in several days even when food floats right in front of him (which, in the past, any amount of food in the tank would result in frantic stuffing of his mouth with sand!).  I cannot reach him without un-piling all of this rock and felt I could probably just leave him to the 'elements' where his shell would provide calcium back to the tank like when he molts. <<Indeed...and likely those "elements" have already dealt with the crabs flesh/organs.>> Is there a downside I should be aware of in this situation or is  this OK? <<A moot point by now I'm sure...nothing to worry about.  The micro-fauna, as well as other macro-fauna in your tank will have quickly dealt with any decaying matter. Mark <<Regards, EricR>>

Google: hermits, health, chemistry  2/6/06 I have a fairly simple question, I have a 29 gallon with an ocellaris pair (with BTA), a pistol shrimp, some Nassarius snails, and a blue legged hermit cleaning crew of about 12 or so. Nitrates, Nitrites, and Ammonia are as low as the testing kits can register, pH is a bit low, around 8.0 but everything seems fine water wise. But for some reason I lose hermits every now and then. One or two at a time every couple weeks. Is this normal? Should I be providing them extra food? Any advice would be helpful. Thanks <Isn't atypical... due to small volume/chemical vacillations... the anemone uptaking biomineral and alkalinity mainly. Please read here: Google: hermits, health, chemistry: http://www.google.com/custom?q=hermits%2C+health%2C+chemistry&sitesearch=wetwebmedia.com Bob Fenner> Molting for 5 months?   1/7/06 Hello, <Hi there> I have a large baseball-sized crab that has been molting (buried deep in the sand) for 5 months! I'm getting concerned. Do I have cause to be? Does it ever take this long to molt or should I expect the worst? I have always heard large crabs take a long time to molt....but this long?? Thanks for any info! Jenn <This is way too long... you are right to be concerned... Something is amiss here... likely either a nutritional component and/or a lacking in water quality (insufficient biomineral, iodine...). Bob Fenner>

Random Mithrax crab death or mating?  11/10/05 Hi crew, <Marc> So my first mystery. I came home today to find one of my 2 Mithrax crabs dead. Face first in the sand. He was about 1.75-2 inches from leg to leg and 1.25 inch in the body. A tough loss for me as they were my very first inhabitants. So, things I checked/noticed:  -Ammonia, Nitrite = 0, Nitrate at .2 or less.  -Have an unfortunate crop of glass anemone popping up, and I hated to do it, but went after a few yesterday with Joe's Juice. <Uhh, this could be the cause here> Will be adding peppermint shrimp and maybe a copper band butterfly soon. -Water temp steady at 78. Salinity maybe a bit high, in the 1.025 range. -Added a small dose of Iodine yesterday also. <With testing...?> -Protein skimmer working well. -PH 8.2 -3 days ago, though I probably don't need it, I added a PhosBan reactor, which is running at about 50gph. <This could do it as well> Though I have low phosphate I've been increasing my sparse feeding regime as my wife things the fish are hungry all the time and I think I've been underfeeding. Setup, 72 gallons with 40 gallon sump and 20 gallon refugia. Sump has 12 gallon RDP refugium with Chaeto. The 20 gallon is an unlit DSB, 7 inches deep w/ sugar fine aragonite.  Now 4 months old but the tank cycled in less then 2 weeks from the quality of rock. Oh, and 100lbs of Tonga branch, and 3/4" aragonite sand bed in the display. Lots of light (2x96 PC 12 hrs and 2x175 HQI 9 hrs).  Inhabitants: 2 ocellaris clown 1 Foxface rabbit fish 1 hippo tang 2 clearer shrimp 2 fighting tiger conch 2 serpent stars 24-30 Astrea snails 4 Mexican turbo 1 pulsing xenia Variety of mushrooms Small Hammer Coral Small Blastomussa (sp?) Small Star polyp coral (doing well) Couple of small hard corals (blue ridge) 1 5" BTA (who is healthy but keeps moving into crevices because the clowns seem a bit tough on him, but I keep turning his rock so he can stay in the open). <<Stop doing that.>> Several small colonies of Polyps 1 4" Plate/Fungia 1 4" metallic green brain AND MAYBE, a mantis shrimp. I haven't seem him, by I hear popping from the tank from time to time.  So I'm not too concerned as the other inhabitants look healthy but I want to be prudent.  Is the Mantis a suspect? <Mmm, no... you would find only bits of shell...> Could this be a function of mating?  <No...> I'm told by my LFS that I have superb water quality in general, especially since my tank is already becoming covered with coralline on the back wall. Was he underfed as I feed a small amount of flake food once a day and then supplement with micro plankton ever 2 days and macro (Mysis) once every 2? Or did he just die from being old? <Likely resultant from one, a combination of the recent changes mentioned above> Just trying to be prudent as I'm trying to analyze my first death in my reef. Thanks as always, you guys are the best! <Thanks and welcome. Bob Fenner>

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.>

Black Gill Disease - 08/20/2005 I want to know cause and prevent method black gills disease in crabs. <Please read here:   http://www.indian-ocean.org/bioinformatics/prawns/GIF/DISEASE/Black.htm .  In ornamental aquaria, this is usually caused by basic poor water quality, or toxins in the water; prevention is simply maintaining optimal water quality.  -Sabrina>

- Help, Crabs Dying, Follow-up - Thanks J! <My pleasure.> We are going to slow down and I took several deep breath's!  LOL - good advice. <Works in most circumstances.> Thanks for the info on the Coral Beauty, she looks great, eats great - she has the food gone in 30 seconds or less! <Sounds good.> I will watch her if I get worried again. Glad to have so many experience people like yourself to help us along - it is the LFS's that continue to "sell" us stuff before it is ready, they don't care if you crash your stuff I guess as they think you will just be back for more... too bad, not good long term business plan. <No, but most businesses of this type are worried about the here and now, the immediacy of paying the bills.> Thanks again! Do you have any preference for Alkalinity and Ca testers or test kits? <I've always liked the Sera tests, the SeaTest(s) are pretty good too.> Don't mind paying a lot for ones that are worth it! <Well... you can spend lots of dollars on nice kits, the ones I mention are reasonable. If money is no object, the Hach and/or LaMotte kits are excellent.> Anne & Rick <Cheers, J -- >

-Flipping over the crab is getting old...- I have a 30 gallon tall saltwater tank. It has been running for several months now. I was given a quarter sized emerald crab by a friend of mine. It was fine in his tank, but now it keeps flipping over on its back and doesn't seem to be eating. <Hmmm...> I have tested ph, SG, ammonia, nitrites, nitrates. All are in normal bounds. Tank mates are a Toby puffer, Spotted Cardinal fish, and a few Red legged hermits. I can not find anything relating to this behavior anywhere. <I've heard of many situations (and witnessed one or two times in my own aquaria) of these guys seemingly doing well, then literally falling over dead. My first thought was starvation, but I'm still not sure.> When I flip it over, (which I have stopped doing) in no time it has flipped back over again. It does seem to favor one of its back legs, but there is no visible damage anywhere. This has been going on for several weeks now. Any ideas what could be going on? <No doubt something is wrong with the crab, but it's unlikely that you can do anything about it. It's not clear what causes these guys to go south, whether it has to do with the transport or tank parameters, who knows. I'm sorry I can't really give you a useful answer!> Nothing is amiss with anything else in tank. Thank you bunches for any input you might have. <It sounds like the rest of your tank is in good shape, I'm sure that the state the crab is in is not your fault. Good luck! -Kevin> Kathy 

Emerald Mithrax (Mithraculus) crab mites? Hey crew, thanks for the excellent advice! <always welcome> I just bought another emerald Mithrax crab from the LFS and while examining it in the bag, I noticed a lot of very small quite objects possibly mites) running around the crab very quickly.  I could not find any specific information on the site regarding these.   <hmmm... are you sure they simply are not harmless copepods (common) scurrying about the animal?> I do not want to introduce anything into my tank that may be adverse and even though quarantined, I can't imagine these will just disappear.   <actually... its what QT is for. You will see after 4 weeks that they are harmless or made the crab/condition worse. Simply QT here my friend and time will tell> Should I euthanize it or are these organisms common and ok for the system? <yikes! Ah, no. Patience and QT is all> thanks for the advice. Shove Willy <rock on my broth. Anthony>

Crab Concerns... Hello there, Hi there! Scott F. here today!> First let me say what a wonderful website! Very informative. I had a question however I've not been able to find the answer to. About a month ago I purchased three crabs from a pet store. I'm not sure what kind they are (small red). They all recently molted, were eating well and so forth. But recently, two females died. I have only the male remaining. I noticed the two females kept flipping themselves over on their backs and exposing their abdomen. They'd 'open' their shells and just lay there. I thought perhaps after molting it was a mating behaviour. However,  About 3-4 days later, both died. The tank seems healthy. I can't find any information on what may have happened. Can you help? I do not wish to purchase any more crabs without knowing more. Thanks in advance. Patricia. <Well, Patricia, I think that the most important step to preventing future problems would be to find out exactly what species you will be keeping. There are a lot of variables which can impact the health of crustaceans, ranging from collection and handling practices, to diet and husbandry. Do try to find out what species you'll be working with, and do some internet searching regarding the species and its requirements. There is a tremendous amount of information on these animals all over WWM and the internet...Sorry I could not be more specific, but this is the best way to start. Good luck! Regards, Scott F.>

His Crab Crashed... Hi, I just bought my first saltwater tank and when I got it, I also bought some emerald   crabs (although one is red). This morning I looked inside to see 2 red crabs but one was dead. It didn't look as if the other one had molted because the dead crab looked like a whole crab! And it was much smaller than the other one...about the size of a dime, maybe a little smaller. What do you think happened? Thank you. <Well, it's hard to be 100% certain, but I'll hazard a guess. Crustaceans, like fishes, do need to acclimate to new environments. They are subjected to the same rigors of capture, transport, and handling, and may not handle these rigors well in many cases. The fact that the animal died so quickly makes me think that this was the cause. In the future, be sure to utilize an acclimation and quarantine technique (see our vast WWM articles section for more on the processes and techniques involved) with all new animals, and I'm sure that your odds of success will increase. In the mean time, do a set of water tests for basic parameters (the usual- ammonia, nitrite, pH, etc.) and make sure everything is in line. Assuming all parameters are acceptable, it is very likely that stress or some pre-existing condition in the animal lead to it's untimely death. I'm sure that with a few adjustments to your new animal acclimation procedures, you'll be fine in the future! Good luck! Regards, Scott F>

Sad crab just the other day my anemone crab started its monthly molt. it usually takes about a day or so to complete the process (most of it is at night). so anyways, this time was a total bungle. this is the third day and its been having problems with the molt. I feared it would suffocate on the first day so I -carefully- aided in the removal of its top main shell (don't know the technical term). I broke just enough off so that its gills weren't covered and left the rest up to it. well the molt is pretty much over with, but the crab had to ditch both of its main claws and about 50% of its legs. it only has one of its 'filter' claws. as far as I can tell both sets of oral pincers are ok, so it can eat. anyways id rather write this one off and ditch it, but alas I've grow fond of the little bugger. I placed him near an outcropping of rock so that it has something to hold on to (otherwise its pretty much on its back or drifting around). and am dropping some roe very close to him every now and again. I know crabs can recover from loss of limbs, but this is pretty bad. it definitely wouldn't last in the wild. got any advice? <Don't help animals in ecdysis... they can/will molt in due time... on their own... Keep track of alkalinity and biomineral content with these animals and make available materials (rock, substrate) that they can/will incorporate in their diet for purposes of biomineralization. Provide plenty of cover of different size hiding spaces...> thanks Jon Trowbridge ps. no other 'animals' in there except some corals and a few urchins/snails. nobody will bug it. perhaps there's a Ca problem? am using Kalk as well (iodide/strontium/CoralVite/Coralaccel). <So... are these at reasonable levels? 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>

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)

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