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FAQs on "Other" Freshwater Crab species

FAQs on FW Crabs by Species: Halloween Crabs, Panther Crabs, Vampire Crabs (Geosesarma Bicolor),

Related Articles: Fresh to Brackish Crabs, Freshwater Crustaceans, Invertebrates for Freshwater Aquariums by Neale Monks, Forget Crawfish Pie, Let's Make a Crawfish Tank! By Gage Harford

Related FAQs: Freshwater Crabs 1, & FAQs on: FW Crab Identification, FW Crab Behavior, FW Crab Compatibility, FW Crab Selection, FW Crab Systems, FW Crab Feeding, FW Crab Disease, FW Crab Reproduction, Fresh to Brackish Water Crabs, FW Crustaceans 1, FW Crustaceans 2, Terrestrial Hermit Crabs, & Marine: Hermit ID, Hermit Behavior, Hermit Compatibility, Hermit Selection, Hermit Systems, Hermit Feeding, Hermit Reproduction, Hermit Disease/Health,


Red Claw Crab not Eating 12/29/19
Hello! Hardly anyone knows anything about red claw crabs, as I cannot find any answers as to why my red claw crab has stopped eating!
<Let's see if we can help.>
He is kept in brackish water conditions, has filtered water, and water that is always about 74 degrees Fahrenheit.
<Right. Let's review first. By "brackish", how salty are we talking about? The first thing you do when brackish water animals misbehave is change the salinity. Many if not most come from places where the salinity varies, so just making a change can have a positive effect. But the bigger issue is that you need to be using a substantial amount of salt, not the teaspoon per gallon amounts often mentioned. I'd suggest one teaspoon per litre (i.e., a salt concentration of about 6 gram/litre) to produce about one-sixth normal seawater salinity. If that didn't do the trick, feel free to double that amount, which would get you around one-third normal seawater salinity. Either of these would be much closer to real world situations for Perisesarma bidens. Next up, review air temperature. 23 C/74 F is very much towards the low end for a tropical animal, and I'd crank the water heater up to 25 C/ 77 F. In cold conditions tropical animals will slowly lose vigour, and loss of appetite is an extremely common symptom of that. Death invariably follows soon after, though it may take weeks to happen.>
He is able to climb to get air or be in water when he wants. I have sand substrate. When I first got him, he would eat his food fine, but now, he won’t eat at all. I noticed he wouldn’t eat, so I ended up putting his food right in front of him, and he still won’t eat that food.
<Loss of appetite in crabs is almost always a symptom of environmental problems. Review as stated above.>
I don’t think he’s molting, because he’s been acting this way for about 2 weeks and I was told molting should only take about a day.
<Correct, and moulting crabs tend to hide away. They do need a source of iodine to moult successfully, for which purpose either offer regular portions iodine-rich foods (Sushi Nori is ideal) or else specific iodine-enriched crustacean foods sold for use in marine aquaria.>
Also, I don’t think it’s a calcium problem, as I give him special vitamins that help provide him calcium every 3 weeks. I’m really worried about him, and I have no idea why he is not eating.
<Hope this helps. Cheers, Neale.>
Re: Red Claw Crab not Eating       1/1/2020

Thank you very much for this help! Right after I added more salt, he molted the next day.
Does he absolutely need to eat his exoskeleton? If so, he is not eating it.
<No, he doesn't need to eat it, but most crabs do, simply to recycle the calcium. If he doesn't, that's fine, but do add some suitable replacement, like a small shell-on prawn that he can pick apart and consume. Failing that, just dusting whatever he likes to eat (fish meat, banana, etc.) with crushed cuttlebone or even fragments of edible snail shells (escargot) will have the same usefulness. Some crab foods are calcium-enriched and may be good enough on their own, but personally, I'd make a point of offering
extra calcium immediately after moulting. Cheers, Neale.>
Re: Red Claw Crab not Eating   1/11/20

I’d like to thank you for helping me with my red claw crab. Unfortunately, he has passed away even after adding a proper amount of salt and turning up the temperature, as he just did not eat at all.
<I'm sorry to hear that.>
I don’t know the reason for his refusal to eat, but after taking your advice, he seemed to have more energy and would actually approach the food (but still didn’t eat it). Maybe he was sick?
<Indeed, or perhaps, he'd been away from salty water for too long. These are tricky animals to keep well -- they need brackish water, high humidity (cold or dry air quickly kills them), and food that contains all the nutrients including iodine and calcium. So while inexpensive in themselves, and not demanding in terms of space, they are tricky.>
I don’t know, but I’m glad I found your website and got some help. You are very knowledgeable about these creatures, and people who are having trouble with their pet crabs are fortunate enough to be able to contact you for help. Again, thank you very much.
<You are most welcome, and thanks for these kind words. Good luck with your next pet! Cheers, Neale.>

Purple Matano Crab Breeding      7/26/17
Hello Wet Web Media Crew, I wanted to follow up and see about the answers to my questions. Are you guys stumped like I am, or are you trying to do some research of your own to better answer my questions?
<First I've seen of this question, to be honest!>
This is the first time I've waited so long for a response (having been a week today), but I know these are advanced questions that I haven't been able to find an easy answer to. That being said, take as much time as you
need, just let me know what's going on, please. I might redesign the system I'm planning to house them in if certain factors won't work out or aren't necessary.
*Details of the planned system* I'd like to set up a system for these crabs using 6 or 7 ten gallon aquariums that will be flow-through (since I'm not sure what determines their sex), but am concerned with issues with such a
system. For example, seeing as I plan to put a thin layer (half inch, maybe) of pool filter sand, a structure of rocks along the back and coming forward about 1/3 of the length of the tank (the tanks will be situated to provide maximum possible number of tanks with the "ends" [side panels] in the front and back instead of how is typically thought of), and a nice piece of driftwood front and center, I want to make sure the crabs will be happy and not have any water quality issues. The other key factor of this is the DIY PVC overflow with the water level only being a third to half way to the top (with a lid) to allow the crabs to exit the water if desired.
With such a low water level, I'm concerned with the feasibility of pumping water to the first tank and having an operating DIY PVC overflow to transfer that water to each of the other tanks as per the King of DIY's video on the subject.
<I agree with your concerns here. Even strictly freshwater crabs run the risk of clambering out of a tank if they can -- in the wild even saltwater crabs will leave rock pools in search of new homes if they feel confined or
stressed. So while your basic idea is fine, I'd be working around the idea of either (a) a single tank per crab with a fully enclosed filtration system; or (b) a large tank divided up with egg crate or cichlid tank separator to keep individual crabs separate but allowing for a free flow of water between the compartments. This latter is how I kept multiple Mantis Shrimps and works extremely well if done right.>
I also plan to have the seventh 10 gallon (or a plastic tote of larger volume) be the filtration unit for this rack. The overflows will transfer water from the front of one tank to the back of the next, with the water exiting and forming a sort of waterfall on the stack of river stones I plan to purchase and place. The pump will use a similar methodology, except pumping water from the back of the filtration unit enclosure to the back of the first 10 gallon in the series, as the final overflow (on the sixth aquarium) will simply overflow directly across (or down, if I keep the filtration below the rack) to save on resources.
<You *will* need to find a way to keep the crabs from escaping.>
*Concerns I'm facing, and some of why I asked the questions I did last week* If the crabs' sex isn't based on a factor such as conspecifics (other crabs of the same species) that are in the same area and their sex, but is
instead determined by temperature, genetics, or other such factors from a young age or during the prime of development, such a flow-through system is entirely unnecessary. I'm providing the flow-through since the sex might be determined by conspecifics in the same "area" (or rack, as the case may be in my tanks). Not sure what would happen with a crab that is completely isolated as far as developing into a male or a female, but that's not
something I want to test with these parental generation crabs.
<Have these crabs been bred in captivity? I'm finding very little about Syntripsa spp. reproduction. Freshwater crabs have wildly varying modes of reproduction, from the basic model (march to the sea/river, release planktonic eggs and hope for the best) through to species that brood their eggs like crayfish do, releasing miniature versions of themselves only when the baby crabs are developed enough to fend for themselves. Without knowing about Syntripsa reproduction, I think it's really difficult to plan a tank specifically for their breeding. My guess would be (as lake dwellers) that they either brood eggs or release relatively large eggs that quickly hatch into baby crabs, rather than having a prolonged planktonic stage, but I really have no idea. This is something you'll have to research. Obviously rearing crabs with a planktonic phase is hard. Sexing crabs is fairly easy though -- females tend to be smaller and have a broad flap-like 'apron' under the body whereas the males have a much narrower equivalent structure.>
*Conclusion* These are all answers I hope to answer with every type of freshwater, brackish water, and saltwater crab I might keep in the future (though I may stick with just the freshwater ones since there's so many),
along with many other questions I'm coming up with as things progress. The distinct lack of scientific info and inquiry on many crabs we keep in the hobby are why I've chosen to do this and focus on truly freshwater crabs
for the time being, possibly expanding into brackish water and saltwater in the future as mentioned. I fall in love with the Purple Matano Crabs I currently keep on a nearly daily basis, so the passion is there. I was just hoping you could help me out with some of this seeing as I would like to keep them properly, breed them successfully (to study the crablets, as well as having a source of revenue in the future), and ultimately further our knowledge base of these wonderful creatures. That being said, I completely understand if you guys don't know or can't answer certain parts of my questions. It's been difficult to find much info on these questions, but that's why I ventured to ask you since you guys are expert biologists from my understanding and I just have my Bachelor's in Conservation Ecology (BS from Arizona State University, 2017).
<A good grounding for what you plan to do, no doubt. I'd be hitting Google Scholar, finding out about Syntripsa spp. in terms of reproduction; and where lacking, making comparisons with its close relatives among the Parathelphusidae.>
Thank you once again. I hope you can provide some insight into the challenging questions presented in my previous email that I've expanded on in this one to follow up.
Best Regards, Jacob
<Good luck! Neale.>
Re: Purple Matano Crab Breeding      7/26/17

Neale, From my understanding, true freshwater crabs are those that have the suppressed larval stage.
<Seems reasonable, but recall that many freshwater shrimps have a marine larval stage. I think you would need to confirm the ecology of your chose Syntripsa species before planning on breeding them.>
Such crabs ... as you mentioned ... have fully developed crablets hatch out of the eggs. Others that march to the sea may be classified in a family of land crabs while not being truly freshwater since they still need some
fashion of saltwater to reproduce. I didn't know about the releasing of eggs that hatch into crablets, though! I thought they all brooded the eggs like crayfish.
<Since freshwater crabs evolved multiple times in many families, I'm sure there's great variation. I simply don't know enough about this group to be sure -- but as a zoologist, I'm minded to be skeptical of any hard-and-fast
I have tried the egg crate method of separation for these crabs in my 100 gallon. Unfortunately, as I was introducing them into the tank one climbed through.
<Try tank dividers then; PennPlax make quite nice, easy to install ones. If possible, combine with undergravel filtration because these do restrict water flow, which undergravel filters bypass rather well.>
Several then followed suit (all except the largest could climb through)...
I documented it in one of my YouTube videos. Once they get to breeding size I might revisit it, but until then I'll likely just try to have separate filtration with a mattenburg filter just behind the start of the waterfall.
Should be interesting to find out what the two juveniles develop into.
I hope I can figure out at what point to introduce the two crabs together (male and female), as well as the technique I 'should' use so I don't end up accidently killing the only female I know I have so far.
<I fear trial and error! But more realistically, large tanks might help by reducing stocking density, as well as numerous hiding places so that females can hide away when required. Ideally, if males/females very different in size, burrows only the female can fit in. Much like breeding aggressive cichlids, really.>
Would you recommend me looking into how others breed brackish and saltwater crabs for such info on the technique of intensively breeding crabs?
<Worth a shot! Crab farming is a thing, so you will find info online about Mud Crabs (Scylla serrata) and other species farmed in tropical Asia and Australia.>
Do you know anyone I can contact specifically, or do you possibly have advice you can give me from your own experiences?
<I know of none personally, and I would imagine that with these new aquarium species, any aquarist who knows about breeding them would be extremely secretive about it! But you could certainly try the usual forums like Planet Inverts and Pet Shrimps.>
These and related crabs have little info at all that has been studied scientifically using the scientific method, and likewise I don't think such crabs have been bred in captivity.
<Nor do I.>
I'll definitely do more research into these crabs, though. Thanks again!
<Cheers, Neale.>

New tank setup and stocking questions... More study; rdg.     6/13/14
Hi crew I've just bought a 6 gallon Fluval edge that I plan to setup on my desk but I'm uncertain of how I want to stock it.
<Mmm; have you read here?:
It is going to be a planted tank with small driftwood and Manzanita with eco complete substrate. I was planning on just some shrimp and maybe Thai Microcrabs.
<Mmm, the crabs will eat the shrimp; and each other if hungry>

Right now I'm leaning towards Sakura Fire Red shrimp and Thai Microcrabs but I don't know quantities to prevent over stocking in a small tank or if the water chemistry needs are compatible for those two species. I'm also undecided on the species of shrimp. I want something colorful, breeds easily, and is easier to care for so I'm open to suggestions on the species of shrimp.
<... ? See WWM re... >

I'm also curious if the tank could handle adding CPD's or another small fish bio and swim space wise with the shrimp and microcrabs but that's just an idea for the moment. I'll have plenty of time to find out what to stock it with waiting for it to cycle.
I also have a planted 60 gallon tank that I would like to change/add stock in. It has 2 Raphael catfish, 1 golden algae eater, 4 kuhli loaches, 1 German Blue Ram, 1 pearl gourami, 3 bamboo shrimp, 1 Farlowella, and 8
tiger barbs. Specs are temp 79-80, ph 7.5, kH 4, gH 3, nitrates less than 20, and 0 nitrites or ammonia. When I set that tank up I only knew basic needs to start a tank but I didn't look into compatibility of the inhabitants.
<? Why are you writing instead of reading? Look up what you have, its compatibility... >

I would like to add another German Blue Ram and maybe 2 electric blue rams to the tank but I don't want to add to that tank unless I know everything is compatible in water chemistry. I want to add more shrimp but anything smaller than the bamboo shrimp I'm afraid would be an expensive snack. I would like to add a vampire shrimp to that tank but I'm not sure what it needs for chemistry. I would also take any suggestions for colorful or attractive fish I could add to liven up my aquarium.
<... reading. Bob Fenner>
Thanks your crew and site are always helpful
New tank setup and stocking questions. Neale's go      6/14/14

Hi crew I've just bought a 6 gallon Fluval edge that I plan to setup on my desk but I'm uncertain of how I want to stock it. It is going to be a planted tank with small driftwood and Manzanita with eco complete
substrate. I was planning on just some shrimp and maybe Thai Microcrabs.
Right now I'm leaning towards Sakura Fire Red shrimp and Thai Microcrabs but I don't know quantities to prevent over stocking in a small tank or if the water chemistry needs are compatible for those two species. I'm also undecided on the species of shrimp. I want something colorful, breeds easily, and is easier to care for so I'm open to suggestions on the species of shrimp.
<Any of the Cherry Shrimp species, Neocaridina heteropoda, are obvious choices. Lots of colour forms, including the famous red one but also blue, green, orange and black. Indeed, Neocaridina generally seem easy to breed.
Neocaridina palmata and Neocaridina zhangjiajiensis are easy too. Caridina species like Caridina trifasciata are smaller and I think generally more delicate and harder to breed (or even impossible if they have a part-marine life cycle).>
I'm also curious if the tank could handle adding CPD's or another small fish bio and swim space wise with the shrimp and microcrabs but that's just an idea for the moment. I'll have plenty of time to find out what to stock it with waiting for it to cycle.
I also have a planted 60 gallon tank that I would like to change/add stock in. It has 2 Raphael catfish, 1 golden algae eater, 4 kuhli loaches, 1 German Blue Ram, 1 pearl gourami, 3 bamboo shrimp, 1 Farlowella, and 8 tiger barbs. Specs are temp 79-80, ph 7.5, kH 4, gH 3, nitrates less than 20, and 0 nitrites or ammonia. When I set that tank up I only knew basic needs to start a tank but I didn't look into compatibility of the inhabitants. I would like to add another German Blue Ram and maybe 2 electric blue rams to the tank but I don't want to add to that tank unless I know everything is compatible in water chemistry.
<To be honest the Rams are going to need much warmer water than the Farlowella, which are very delicate fish that need cool, fast-flowing water with lots of oxygen. Bamboo Shrimps like much the same conditions as the Farlowella. Golden Algae Eaters are a menace when mature, so do review this species (Gyrinocheilus aymonieri) and act accordingly.>
I want to add more shrimp but anything smaller than the bamboo shrimp I'm afraid would be an expensive snack.
<Indeed; the Striped Raphael are predators on all sorts of shelled inverts, including snails, let alone shrimps.>
I would like to add a vampire shrimp to that tank but I'm not sure what it needs for chemistry. I would also take any suggestions for colorful or attractive fish I could add to liven up my aquarium.
<Keep reading before spending anymore money. Vampire Shrimps, indeed, all Atyopsis species, are very demanding in the long term. They are pretty much filter feeders, and while they can eat from the substrate, inefficiently, they don't compete well with catfish. They're also rather vulnerable at moulting not to mention sensitive to medications like copper.>
Thanks your crew and site are always helpful
<Most welcome and thanks for the kind words. Neale.>

Malawi Blue Crab (Potamonautes orbitospinus)    10/31/12
Hello. I found this interesting crab and want some info. How big do they grow?
<Big; 15 cm/6 inches or wider across the shell.>
Do they go through a larval stage?
<For this species, unknown to me, but some other Potamonautes are known to have a completely suppressed larval stage, i.e., the mother holds onto the eggs until fully-formed "mini crabs" are released.>
How would I get these to breed?
<Probably impossible under home aquarium conditions; see below.>
How big of an aquarium would I need to house one male and one female?
<This species is reported to be extremely aggressive towards its own kind, much like practically every other non-micro crab imported into the hobby. So keeping more than one specimen is a risky venture.>
Are they fully aquatic?
<More or less, but they are notorious climbers and escape-artists. In the wild they are somewhat amphibious, resting in burrows above the waterline, but mostly feeding underwater.>
What water parameters should I keep them at? I heard any parameters Malawi cichlids can be kept at, these can be kept at. Is this true?
Lastly, what type of setup would you recommend for these crabs?
<A very, VERY secure aquarium, perhaps with a rocky island or two for them to come out of the water if they want to.>
I want to breed these to supplement my income and for the occasional treat (I've never had crab but my family loves crab and I want to try some). I think these would be good to sale because they are big enough to be eaten and they are relatively rare in the US and Canadian aquarium trade.
<I'm not sure this species makes much sense for this sort of venture. There are lots of other fish and shrimp species that can be bred at home and make a decent profit when sold to retailers -- ask your local retailer what he or she could sell profitably, and take if from there! Dwarf Gouramis for example are a good fish species to try because the farmed ones are so healthy, while some of the most popular shrimp varieties like Crystal Red Shrimps still make a good price. As for eating quality, do review carefully the literature here: home aquaria are Salmonella incubators!>
Thank you for taking the time to answer my questions!
<Welcome, Neale.>
Re: Malawi Blue Crab (Potamonautes orbitospinus)

Thanks for responding so quickly. I did not know that part about Salmonella. Thank you for telling me.
<No problem! Cheers, Neale.>

Goa land crab ID 8/21/11
Sir, I have found a crab in my garden it was crawling on the wall and have problem finding its details on internet hope u will let me know what type of species of crab this is bright pink colour black eyes. is it a rare species or a common one. pls let me know. I am from Goa India just happened to visit your site online while looking for information.
regards. sample pics and clips attached
Elvis John D'souza
<I don't know this species. It's clearly a land crab of some sort, perhaps a Gecarcinus species. But it isn't a species I've seen in the aquarium trade so can't offer you any better help than that. The zoology or ecology department at your local or regional university should be able to help.
Alternatively, a local natural history museum or nature conservation office. Cheers, Neale.>
Re: Elvis Goa India 8/21/11
thanks a lot
Elvis John D'souza
<Most welcome. Do read here: http://www.wetwebmedia.com/fwsubwebindex/fwcrabfaqs.htm
While crabs can make fun pets, they're mostly amphibious and cannot be kept with fish or each other. Review Cardisoma armatum online for the basics.
Cheers, Neale.>

Crab identification 11/17/10
Hello, I was wondering if you could help me identify a large crab that I recently bought from Petco. They had it labeled as a "Thai Red Devil Crab" but all my internet searching on this name has not found any results. He is about 4 1/2 to 5 inches across with a purplish red shell. His left claw is much bigger than his right, but not quite as much of a difference in claw size as Fiddler crabs. On a side note, I was wondering if crabs use their large claw for anything other than attracting the ladies. Anyways, I currently have him in a 10-gallon semi brackish tank (he will be upgraded to a 25 soon) with a cave to hid in and one of those small turtle docks to allow him to get out of the water. Is this setup ok or should I switch to a terrarium? I also included some pictures of him and one of my crayfish for your convenience. Any help would be appreciated.
<Hello Zach. You appear to have a male "Thai Devil Crab". They're periodically traded but I have no idea what their Latin name might be. In any case, they get quite large, and they are notoriously aggressive and predatory. They do appear to be more or less aquatic in the same way as many other estuarine crab species -- i.e., by choice they stay underwater, but that can venture onto land for short periods. An arrangement of rocks above the waterline that allowed the crab to bask under the light should it choose to would be helpful, but otherwise don't worry about providing this beast with a land area. Thai Devil Crabs don't seem to be amphibious in the same way as Soapdish Crabs or Red-Claw Crabs. One clue is their rather flat body compared to the much more boxy, deeper body shape typical of amphibious and land crabs. They do require brackish conditions though, SG 1.005 is ideal, and I'd also recommend using marine aquarium Iodine supplement at about 50% the recommend dosage. Although crabs are carnivorous given the chance, their diet should be distinctly mixed with plenty of green foods alongside meaty treats such as tilapia fillet and unshelled prawns. As for differences in the size of the claws, so far as I know this species has claws of similar size, so your chap has probably lost a claw at some point, and it'll be a few moults until the new claw matches the other claw in size. Crabs do indeed use their claws for all sorts of things, from signaling to one another through to dismembering prey, snipping off vegetation, crushing snail shells, climbing up things, and of course for nipping at anything that attacks them. Crabs are fascinating animals, among the Nature's success stories, and quite a sophisticated and modern group of animals despite their sometimes archaic appearance. Cheers, Neale.>

Re: Crab identification, salt 11/17/10
Hello again and thank you for the quick reply. I don't think my crab lost his claw in a fight as all the other crabs in the tank also had one large and one small claw. He also uses his small claw to pick up food like
fiddler crabs. His large claw has roughly the same proportions to his body as a fiddler but his small claw is a little bigger proportionately. If both his claws were the same size as his left I don't think he could move them. I'm sorry if you didn't get the picture I will paste it to this message. As for the salinity, should I use marine salt or is their a salt specifically made for brackish water? Sorry if that sounds dumb I don't know much about saltwater tanks.
Thanks in advance
<Hi Zach. The claw could easily have been damaged prior to collection.
While it is not uncommon for crabs to have dissimilar sized claws through accidents and fights, Fiddler crabs are exceptional in having one claw massively overdeveloped as a signaling/fighting tool rather than one for feeding and climbing. So far as I know, crabs don't do the lobster thing of having one claw for crushing and one claw for snipping. Yes: marine salt mix is what you need, not "tonic" or "aquarium" salt used for treating freshwater fish. Around nine grammes per litre should be ample, with iodine added. Without the iodine, large crustaceans are extremely prone to moulting problems in captivity. Iodine-rich foods such as Sushi Nori make particularly good supplements to their diet for the same reason. Cheers,
Re: Crab identification, sys 11/17/10
Hi sorry for so many questions (this is the last one) but how long can these crabs live in freshwater? The salt in his tank is "aquarium" salt. I might not be able to get marine salt for a couple days will he be ok until then? I don't know how long Petco had them in freshwater but he's been in my tank 5 days. Thanks.
<Hello Zach. "Aquarium" salt will do for a few weeks, but in the longer term the lack of calcium salts as well as iodine could cause problems. If you can, add 1 teaspoon baking soda (sodium bicarbonate) and 1 tablespoon Epsom salt (magnesium sulfate) per 10 litres alongside the aquarium salt.
These will provide some of the minerals crustaceans need for their shells.
Also, add the iodine, either in the water, or through foods rich in iodine (there are some special crab pellets available from companies like JBL).
Cheers, Neale.>

crab compatibility 11/19/10
Hello, I would like to thank you again for all the info on my Thai Devil Crab. I am going to get him some marine salt this weekend. Anyway, my question is would a devil crab be compatible with a Halloween
crab(Gecarcinus sp.)? I know crabs are aggressive but I figured that since the devil crab is mainly aquatic and the Halloween crab is mainly terrestrial they would pretty much ignore each other. They would both be in a 55 gallon tank, (half water half land) about 4 ft long and 1ft wide.
<Easy one this. No. These large crabs are extremely intolerant of one another and in a small vivarium like yours cannot be reliably kept together. When one crab moults, there's a good chance the other one will
attack it. Cheers, Neale.>

Red Claw Crab Missing Limbs 10/12/10
I purchased 2 Red Claw Crabs from PetSmart.
<Perisesarma bidens'¦
and interesting, if aggressive, brackish water crab.>
I believe one was male and one was female, do to the markings on their underbellies, plus one had slim claws, and the other had fat, wide claws.
<Do bear in mind males and females view each other as food except when mating!>
After about a month, one crab (female) molted. She was seemingly fine after the molt, with all appendages in tact. Two days later, 2 legs and both front claws were missing. I removed the other crab (male), assuming he attacked her. Three days later, the attacked crab died.
<As often happens.>
Am I correct in assuming the other crab attacked her?
<Possibly. When crabs moult they would normally hide in places such as caves or bury themselves in leaf litter. Either way they'd be out of view. Crabs view one another as potential meals, and in their "soft" state they're easy targets. A lot depends on their environment, and in a spacious tank with plenty of hiding places crabs can moult successfully. But if you crab two crabs in 5 or 10 gallon tank, it's hard for them to avoid each other, and if there aren't any good hiding places, and I mean REALLY good hiding places, not some upturned flowerpot, then they can, will attack one another.>
Did the molt have anything to do with what happened here?
<Can certainly be a factor. But bear in mind lack of iodine is a very common reason for failed moulting. Use marine aquarium iodine supplement at 50% the quoted dose per gallon of water. Also make sure their diet is calcium-rich -- a mix of whole lancefish, unshelled shrimp, and suitable soft fruits should do the trick, along with regular offerings of crustaceans foods such as those from JBL, Sera, and others.>
Would the lost appendages result in her death?
<Not in themselves, no, but lack of iodine can cause various problems, deformed appendages merely being the most obvious symptom.>
Also, I've read on your site that RCC are land crabs, but mine stayed in the water most of the time.
<Well, they are land animals. In the wild they live in estuaries, dipping into brackish or salt water periodically but foraging on land. On the other hand, for a variety of reasons they may prefer to stay underwater in a given aquarium, perhaps because there's only enough dry land for one dominant individual. Cold and dry air can also stress them.>
My tank set-up: 10 gallon tank, part land, part water. Sea salt mixture added to water,
<How much? You really need brackish water, not "teaspoon per gallon" amounts of salt. Use marine aquarium salt at not less than 6 grammes per litre (~3.8 US gallons), and ideally 9 grammes/litre, for a specific gravity of at least 1.003 and ideally 1.005 or more at 25 C.>
with calcium and other trace elements especially for invertebrates.
<Iodine is the key, and yes, you do need iodine supplement.>
Utilized a terrarium filter to clean the water. Fed spirulina flakes, bloodworms, krill, and crab pellets. No heater was used in the water.
<Well, that's one problem. They are tropical animals. The air needs to warm and moist. Essentially you're creating a habitat similar to what you would for tree frogs, except the bathing pool contains brackish rather than fresh water. Apart from that, the coconut fibre substrate will be similar, and the bogwood and plastic climbing branches will be similar.>
After this experience, I do not believe PetSmart should be selling these crabs.
<Difficult to argue against. But they are bizarre animals, and some dedicated individuals have even bred them! The larvae need to be moved into seawater conditions and fed tiny live foods, but it is possible.>
They seem to be aggressive towards one another,
<As are virtually all crabs.>
and their requirements go way beyond what the pet store would have you believe.
<Same with Goldfish, to be honest.>
I wouldn't recommend them as a pet for the average person.
<The huge problem is that the "average person" doesn't usually keep pet animals terribly well. How many dogs do you know that get short, infrequent walks? How many parrots do you know living in small cages? How many Goldfish do you know get in bowls or small aquaria? You and I are different in caring about how animals are maintained in the home; the average person often doesn't care all that much -- or perhaps more charitably, doesn't understand how badly they're treating their pets.>
Thank you for any information you can give! Your website is awesome!
<Kind of you to say so.>
Lorie Masi
<Cheers, Neale.>

Info On Mini Crabs <Micro Crabs> 6/11/09
While I have learned much of what I know of the aquarium hobby from your website, I am unable to find information on micro crabs (aka Thai micro crabs, mini crabs, hairy mini crabs, scientific name possibly Limnopilos naiyanetri but I'm not sure on that).
From the little info I have been able to find on other sites, I am led to believe that they are freshwater, don't need land, hang out in plants, act like cherry shrimp, and like tropical temperatures - I've read anywhere
between 64 Fahrenheit and 86....that's a pretty big range....
If someone knows about these adorable little guys, I would be ever-so grateful if s/he would share that knowledge, or even direct me to a legitimate informational site or book. Of course I would love to add them
to one or more of my setups, but would never do that without first learning about their water preferences, temperament, compatibility (it seems they are more likely to be eaten by larger creatures than to cause harm
themselves?), nutritional needs, etc.
<Limnopilos naiyanetri, has just been discovered by hobbyists in the early 90's. About all I can tell you is that these crabs are found in pure freshwater in the roots of floating vegetation, such as water hyacinth and fine leaf plants along river banks. They have hairy bodies and appendages which collect mud and dirt and may function to trap food particles. They are not carnivorous, and behave like Caridina shrimps in their scavenging behaviors, where care and feeding are probably the same.
Googling will likely lead you to more information on the micro crabs. I know of no book written on the subject and Bob and/or another crew member may input here with additional info on the micro crab.>
Thanks in advance!
<You're welcome. James (Salty Dog)>

Crabby Crab?  Sabrina Has Crab Envy! - 09/03/2005 Just bought an apparently Yellow Moon crab from the local garden centre.   <Research prior to purchase, next time....  I'm impressed, I suspect you have Geothelphusa albogilva.  This animal is currently unobtainable in the US.> Guy said it was ok in my tank with 3 goldfish which are very big.   <Likely untrue.> Got the heater for him and the right food etc.   <Goldfish are coldwater, shouldn't be heated.> He seems to want to get out of the tank all the time, life seems one big struggle to climb to the top and spend some quality time out of the water on top of the heater or filter system.   <Yup, this and all other crabs available in the freshwater hobby absolutely require a land mass with hiding space - these are land animals that spend some time in the water.  Geothelphusa albogilva is more terrestrial than anything.  At least the animal is actually freshwater.  I sure wish we got critters like that in the hobby in the US.> Can't find any info on these crabs <Not much out there, from a husbandry point of view - treat this like any other terrestrial semi-aquatic crab....  Give it a large land mass of several inches of sand and wood/leaf debris, with a great deal of cover/hiding and a few gallons of clean, circulating freshwater.> and worried I'm not looking after him right.  Can you give me any advice on making sure he has good quality of life?   <Just as above - this is an animal worth accommodating.> Would really appreciate your help and comments. <I'd absolutely LOVE some images of this animal.... please.... if you have time and a camera.  I have crab envy.> Kind regards,  Joanna <Wishing you and your new decapod well,  -Sabrina>
Crabby Crab?  Sabrina Has Crab Envy! - II - 09/07/2005
God I feel so naive.....just thought I was buying a funny cute looking crab to live next to my computer and look nice.  Guess I was major uninformed. <No worries....  The fact that you are seeking information is wonderful.> Didn't realize I had something unusual! Please excuse my ignorance. <Again, no worries.> I am a total animal lover and now dead worried this poor little creature is not getting the right life. I will transfer him to another tank and somehow arrange land for him to rest on and water when he needs it. How come I can easily buy him here and you can't over there? <I have never heard of Geothelphusa offered for sale anywhere....  But Europe and the UK always tend to get "new" critters a few years prior to the US.  There are many shrimp and crabs available in Europe that I'd do a great deal to get my hands on!  I suppose I shall just remain patient....> I will take some pictures of him and send them to you... <Much appreciated!  I would very much like to see if this is in fact the crab I think it is.> again excuse my ignorance as a first time crab owner but what's the interest? He's not yellow or looks like he's from the moon haha, just a small baby crab that's whitish in colour and likes sitting on the heater.   <Once in a proper environment, I suspect you'll find him much more interesting.  The interest, to me, is that I have quite a passion/fascination with invertebrates, especially crabs and shrimp....  the interest with Geothelphusa, to me, is that they don't or shouldn't require saltwater access....  If there were more truely freshwater land crabs available in the hobby, folks would be more easily able to care for them properly, which is one of my main desires....> Guess I'm entering a whole new dimension I didn't know existed out there.   <Invertebrates are really amazing animals!> Would love to chat more, thanks for replying so quick.   <You bet.  Sorry for the delay in this response; I've been traveling a bit.> Where about in the US are you?   <In California....  In the Santa Cruz mountains.  Beautiful place.> I'm over in UK in Yorkshire - God's Country. <Sounds excellent!> Best regards,  Joanna <Wishing you and your crabby pal well,  -Sabrina>

Amarinus lacustris, ID, habitat of a FW Crab from down under  03/09/07 Can you tell me what "Myth" was being referred to here in the question in the following paragraphs? If I understand correctly the myth was concerning Amarinus lacustris. I have been trying to get a few specimens of Amarinus lacustris for a long time. I try to track down every lead but this one is  too cryptic for me to figure out what was being referred to this time.. Michael Hissom Freshwater Invertebrates, ID? Hey guys I am  trying to ID a crab that is appearing more and more frequently in Australian  stores. It has been incorrectly identified by several stores as Amarinus  lacustris (Freshwater spider crab). I suspect the supplier is keeping this myth  alive *lol Anyway, the crab in question is often referred to as a "brown backed  crab". Orange/brown body with a chocolate brown H symbol on its shell. claws of  equal size and quite heavy set, not long/slender. It seems to get to about 2"  shell width. I would LOVE to know the scientific name for this little beauty, as  although I am sure I could keep it happy using general crab knowledge, it would  be nice to know its specifics. Sincerely, Abbey AKA  Callatya <Mmm... well... this could be Amarinus... Please read here: http://www.google.com/search?q=Amarinus+lacustris&rls=com.microsoft:en-us:IE-Address&ie=UTF-8&oe=UTF-8&sourceid=ie7&rlz=1I7PCTA ... and am going to send your query to our resident FW crustacean expert, SabrinaF for her input. Bob Fenner>

The Holy Soap Dish - 03/12/2004 My soap dish crab recently molted about, three weeks ago. <A Cardisoma species....  Perhaps Cardisoma armatum.> He has several holes, or sores, in his pinchers. He seems healthy, but I have not seen this before. Could this be a parasite or is there some deficiency in his diet? Do you know what this is and how I might treat it? <The likeliest thing that comes to mind is a deficiency in iodine.  Are you adding iodine to his water?  I use Kent marine iodine in my freshwater invert tanks, at a rate of ONE drop per TEN gallons, once every week.  I would imagine your crab could/would like to have that increased a bit, though.  The second thing that comes to mind, this species, as well as many/most other freshwater crabs, requires an area to get out of the water.  Without this, they may have health issues, perhaps including what you are describing.  If you don't have such an area, please do consider adding something for him.  Even dropping the water level a bit and adding a ramp/platform of cork bark in the back of the tank would do the trick.> I have had this crab for over a year now and want to keep the creature in good health. <Wonderful to hear.> Thank you,  Bob <Wishing you and your pinchy pal well,  -Sabrina>
Holy Soap Dish - II - 03/21/2004
Sabrina, <That's me!> I will take your advice. Many thanks for your help. There is not a lot of information about these crabs available. <Agreed.  I am SO glad you wrote back, I forgot to add the link I had wanted to give you.  Here's a listing of (mostly) freshwater crabs (also shrimp, crayfish, snails, clams....), auf Deutsch, but otherwise useful for identification - and if you can read it, or translate via Google's language tools, there's lots of valuable info there, too.  So, without further ado,: http://www.wirbellose.de/arten.html#Krabben > It was nice of you to share your expertise.  Regards,  Bob <Glad to have been of service.  Thanks for writing in!  -Sabrina>  

Mystery Crab - 04/06/2004  Hey guys  <Sabrina the freshwater crusty-freak here!>  I am trying to ID a crab that is appearing more and more frequently in Australian stores. It has been incorrectly identified by several stores as Amarinus lacustris (Freshwater spider crab). I suspect the supplier is keeping this myth alive *lol  <Yeah, frankly, I'm still confused on that subject. Here's the only photo/info I've been able to locate on the web about this poorly documented little beast: http://www.nzfreshwater.org/crustacea.html  (scroll down) and http://www.dlwc.nsw.gov.au/care/wetlands/facts/paa/plants/emergent.html  (scroll down to "Cotula coronopifolia - Waterbuttons").>  Anyway, the crab in question is often referred to as a "brown backed crab". Orange/brown body with a chocolate brown H symbol on its shell. claws of equal size and quite heavy set, not long/slender. It seems to get to about 2" shell width.  <Any chance you can snap a pic of this guy to aid in ID'ing him? The following two sources may help you: http://www.wirbellose.de/arten.html#Krabben and  http://www.wetwebmedia.com/marine/inverts/arthropoda/crabs/swcrabs.htm >  I would LOVE to know the scientific name for this little beauty,  <Me, too! I've looked through everything that I have to look through, but without a picture to go off, it's pretty tough to try to find a good ID. I would very much like to see what your fellah looks like!>  as although I am sure I could keep it happy using general crab knowledge, it would be nice to know its specifics.  <Agreed. Always best to know what your animals need - and crabs are pretty diverse.>  Sincerely, Abbey AKA Callatya  <Hope to hear back. -Sabrina>
FW crab from down under info. Hi, This isn't a question - I just happened across your website and noticed a question someone asked about Amarinus lacustris - a genuinely freshwater crab found in S.E. Australia.  Here is a photo if you are interested.  Its about 6-7mm across the carapace.  Although I am no expert, I'm happy to answer any queries anyone might have, although you were quite right in your reply - there is little info available.  It would be illegal to attempt to export this animal. <Thank you for this input. Will post on WWM. Bob Fenner>

Crab Questions - 04/15/2004  Hello Crew-  <Hello, Jessica!>  First of all, I wanted to tell you how much I've learned from your website on the subject of my newly purchased Sesarma bidens <<Now: Perisesarma bidens, Red Claw Crab>>! However, I do have a couple of questions for you, and I know you can help.  <Whew, you're a lot more confidant than I am! But I'll try my best.>  I have a 10gal. freshwater tank for the two crabs I purchased close to two months ago. Both of the "girls", my 12 year-old son lovingly named "Tara" & "Melissa", have been doing wonderfully. They both have been eating well on a diet of algae pellets and shrimp pellets.  <So far, so good.>  But, after checking them both yesterday morning, and then later that afternoon, I discovered "Melissa" was in a normal up-right position, but wasn't moving at all. Maybe I'm being very ignorant and naive, but I didn't want to throw her out until I knew for sure that she wasn't actually dead and could be molting.  <No, I understand. Though, the molting process is usually relatively quick, and they'll usually hide while they molt, and while their new shell hardens.>  I did check her this morning and there's still no movement. I've spent the last three hours culling through information about the crabs, but I've had no luck in finding anything on what a dead crab will look like compared to a molting crab.  <At this point, if she's not moving, I would pretty much suspect the worst. I am very sorry. It may have been aggression from the other crab; this species, like quite a few others, are pretty aggressive with one another.>  We owned a very large hermit crab for five years, so I am very familiar with molting. But I've never owned crabs before.  <They're pretty much the same.... Though I would add iodine to the water (see our shrimp & invert FAQs for details), and would certainly allow them a space where they can get out onto a dry space somewhere in the aquarium; it is quite crucial that they have a land space.>  I also wanted to ask about the actual necessity for salt in the water for these crabs.  <It is unnecessary. They may do somewhat better in brackish water, and certainly need high-end brackish to breed, but should do quite well in freshwater.>  I found a ratio of 1tsp/10gal of kosher salt...it this a correct and safe figure to go with,  <Yes, certainly. You'll still be "fresh" water, essentially. Even salt-sensitive fish can tolerate this concentration.>  and will it hurt goldfish if I choose to put them in the water too?  <The salt would certainly be fine for the goldies - BUT - ten gallons is really far too small for goldfish. I would recommend something simpler in terms of maintenance; goldfish are really far too messy of waste producers to keep in such small confines. How about mollies? These would do exceptionally well, you could keep a few in a ten gallon with the crab, and bring up the salinity, even to full saltwater, if you desired.>  Thank you so much, and I hope to hear from you soon. Jessica Linaweaver  <You are quite welcome; thank you for writing in. Please let us know if you have any further questions! Wishing you and your crab well, -Sabrina>

Molted Crab - 05/31/2004 I have a Red Claw Crab, he is my first crab and I don't know what to do now that he has molted. His old shell/skin is sitting at the bottom of my tank, I don't know if I should remove the skin or leave it in the tank. <I would leave it.><<Often are eaten, reincorporated into new exoskeletons... necessary mineral content. RMF>> I know Hermit crabs need their old skin to eat, but I don't know what to do with this one. <If it's not gone in a few days, pull it out.  I would assume the crab (or other denizens of the tank) will have made short work of it, by then, but if not, best to get it out.  Wishing you and your crab well,  -Sabrina> Shelly Warren

A Sesarma By Any Other Name.... Would Be A Pseudosesarma 10/26/2004 Hi guys... <And gals.  Sabrina-the-freshwater-invert-freak at your service.> We need your help. <Well, what d'y'know, that's what we're here for!  Hope to help you out.> We have been getting conflicting information on our RCC. <For our readers, that's "Red Claw/ed Crab", or as you've mentioned in your subject line, Sesarma bidens....  Actually, this animal is now thought to be more accurately Pseudosesarma moeshi.  Just a fun tidbit.> One thing that everyone seems to agree on, is that RCCs are brilliant escape artists. <True.  Most (all?) crabs are.> However, when we have been trying to research as to whether they actually NEED to breathe air half of the answers are yes, the other half are no. <Mm, not so much that they need to "breathe" air (all land crabs use gills and require high humidity - even hermit crabs, which carry a bit of ocean in their shell!), but yes, they absolutely *require* a land mass to thrive.  They will not last long, forced to be fully submerged....  Or worse, fully submerged in a freshwater aquarium, as they are unfortunately sold to be.  In addition to their need to get out of the water, they also fare much better with some salt in the water.  Doesn't need to be much, but they do much better with a bit of salinity.> Could you please set the record straight for us? <Land mass required, yes.  Most definitely.  It will live for a time fully submerged, but will not thrive, and will not live long.> We don't want the little guy to die, but we don't want him to escape either. <Any chance you could drop the water level a few to several inches and offer a good-sized land mass (even a very large piece of floating wood) with lots of nooks and crannies to hide?  This would likely be sufficient.  I suspect that the reason they are so renowned for escaping is simply that they are desperate to find a way out of the *water*, not the *aquarium*.  All the same, a tight-fitting lid is definitely called for.  Do please try to accommodate this animal rather than returning him; you will be greatly rewarded with a fascinating pet, with just a little work.  Perhaps even a small, 10-gallon tank as a dedicated home for him and an opposite-gender pal?> Thanks so much, <You betcha.  I really hope you choose to make this work out - these are fun critters.> - Ian Fenn <Wishing you and your crab well, -Sabrina>
A Sesarma By Any Other Name.... II - 10/30/2004
Hello again, Gurus of Aquaria! <Well hello!> Thanks so much for your Red Clawed crab-help Sabrina. We finally found someone/place that knows what they are talking about! <Heh, or at least we *hope* we do!  So glad to have been of service.> We were wondering if we could please have some help with our cichlid tank now. <Whups, not me....  I am cichlid-ignorant, for the most part.  Chuck, our mega-awesome cichlid master is in possession of a duplicate email; hopefully he'll give you the answers that you seek.  I'll truncate this now, and give you a big hearty "Thanks!" for all the kind words.  Wishing you well,  -Sabrina>

Anomalous Crab Question - 10/30/2004 Hello, My little red crabs keep getting on the filter and just sit there like they are in a stream. <Er, do you know what kind of crabs these are?  Can you give me a good description of them?  Size, coloration, markings, anything like that?> I do not see how they are getting up there unless they can swim. Why and how do you think that they are doing this? <The how is the easy part.  Crabs are *amazing* for being able to climb nearly anything....  I wouldn't be too terribly shocked if they were simply climbing the glass!  But more likely, they're finding a way up to the filter intake tube, and climbing that.  Now, as for the "why" of it, there are likely a few reasons.  First, is this a fresh, brackish, or saltwater aquarium?  In what country do you live?  In the US, there are nearly - or absolutely - no crabs sold in the hobby that are truly freshwater animals.  Most will survive in freshwater for a time, but they will not thrive and will not live their full life span.  Moreover, nearly - or absolutely - no crabs sold in the trade in the US are truly aquatic.  All are amphibious, or land crabs that only occasionally venture into the water.  Chances are, your little inverts are just trying to find a way out of the water.  At the very, very least, I recommend you drop the water level a bit, and give them a surface to rest on out of the water.  Try to provide them with a few hidey-holes on the surface to help them feel secure.  Remember, crabs are extremely adept escape artists, and they can and will find any way out of the tank, especially if they're not happy with their setup.  Please be sure you have a tight-fitting lid, or you might wake up in the morning to find a crab cuddling you in bed!  ;) > Thank you Kayce <Wishing you well,  -Sabrina> 

Got Crabs? Hi WWM Crew! I have a 20g FW tank. In that tank I have 4 guppies, 5 small goldfish (who will soon have there own tank), and 2 small catfish. I was wondering, can I put some small red crabs in there or will they harm my other fish. The ph is 7.2 and the temperature is consequence at 73* F. Will this cause a problem at all? Please, I would be very happy to hear from you. Thank you: ~Lena~ <Hi Lena, Don here. Sorry, can't recommend crabs. Although some will thrive in FW, most would do better in at least brackish conditions and all would need a place to get out once in a while. If they were to catch a fish they would kill and eat it. There are plenty of FW shrimp you could keep with the guppies and cats. BTW, You do need to move the goldfish and then increase the temp to 78>  

Thai devil Soapdish crab I know this is not truly an aquatic species, so I don't know if you  can help.  However, I thought that if you didn't know the answer, you may  know someone who does. <Mmm, am actually one of those "guilty" ex-retailers of yore who used to sell these w/o much knowledge of their husbandry> My friend has a Thai Devil crab (Soap dish crap).  His large  claw is inflamed at the joint where it attaches to his body.  He is in  a 10 gallon tank, partially filled with water.  He has land access and  spends most of his time there now.  He is still eating as normal and very  active.  The Ph of the water is 7.0, but she does not have any salt  added. <IS a freshwater animal, that DOES eat various meaty foods>   He is fed a varied diet of krill and hermit crab pellets.  She  soaks the krill in vitamins before she feeds them to him. <Good> I understand  that iodine is important to these crabs. <A essential micro-nutrient for much life, including you and I. I would add Lugol's solution, potassium iodide/iodate once a week or so... to this animals water.> Does he need special  lighting? <No> And could the inflammation be a sign of an impending molt?   <Maybe> He is full grown and they only molt once a year I think.  She is very concerned about his health, she has had him for about 6 months.  Any information would be greatly appreciated. Thanks, Caryn <I encourage you to place the above title words in your computer search tools and read what little there is posted on the Net re this crab/species. Bob Fenner>

FW Crabs Hello again. Thanks for taking a look at my letter. I have a few more questions for you. Using the German crab ID page I found on your site, I have determined that my soap dish crab is the third Thai fresh water crab they have listed, it looks just like my little Carl, right down to the dark zig-zags on his appendages. It says it is of the Demanietta species, but that seems to include a lot of different looking crabs. How can I narrow it down further? < Do a Google search on the web using the Demanietta species you have already found. That should get you closer to a correct ID.> Anyways, I've started adding iodine to all my crab tanks. How often should I add the drop? daily? < Add the drop of iodine every time you change water.> The water I use is well-water with a softener. If this is no good, what type of water should I use? Would adding some sea shells add calcium to the water? < All crabs like brackish water. I would use the softened well water but add some sea salt and micronutrients at about 1/3 to 1/2 the dosage recommended for salt water.> I know the fiddlers prefer brackish water, does Carl need some salinity also? < You bet.> Should I change the water to brackish? < The sooner the better.> Would his feeder minnows tolerate the salt? < They are pretty tolerant to salt and would probably do OK.> He has not molted since I have had him, but I just figured he was big enough that he only molted once a year. Am I incorrect with this assumption? < Sounds like a pretty safe assumption.> How big is this guy supposed to get, anyway? What is this creatures lifespan? well, thanks in advance, Scott < They usually get about 2 to three inches across the body and will probably live between 2 and 5 years depending on how old Carl was when he was caught.-Chuck> 


Soapdish Crabs, Fiddlers, Ghost Shrimp hello: please, I was wondering if y'all could help me.  I have what was sold to me as a Soapdish crab in a 2' x1' 6" tank with about 4 or 5 inches of fresh water.  Carl, as he is called, has a 2" wide body and is probably about 6" across including legs.  he has relatively short (compared to my fiddler crabs) eye stalks and is a reddish brown color with orange legs and claws that have reddish brown "designs".   the tips of his claws are whitish gray.  he has easy land access but hardly ever comes out of the water.  is that weird? <Mmm, not necessarily>   he eats live minnows and frozen peas.  anything else I could feed him for a little more variety? <Other meaty foods>   please don't say crabs eat anything, he won't eat carrots or broccoli.   is it safe to feed him hot dog? <Mmm, no... too fatty>   he'll eat it and seems to like it but I took it away because I'm wondering if it could be harmful with all that sodium.  should I remove any left over fish parts from the water?   <Yes, I would> sometimes he just eats half a minnow and the other half  just floats around in the filter current.  will it muck up the water or make it unsafe for him in any way?    <Could. I'd remove all uneaten food> I have had him for probably 8 months and he seems to be doing well.   I just want to know if you guys and girls have any tips to make him happier and/or healthier.  I read something on your site about iodine supplementation for crustaceans? anything else? <You could monitor, adjust biomineral (mainly calcium) and alkalinity... has this animal molted while in your care?> what is krill, where do I get it and how do I "soak it in vitamins"? <Euphausiids... liquid vitamins... just putting a few drops on for ten, fifteen minutes before offering...> I love my soap dish crab(s) and would really appreciate any help y'all could give as there is virtually zip on the web about them. also, for anyone wondering, Carl (as with all Soapdish crabs, in my experience: I have 2 males, I lost a female when she wondered into Carl's territory) is extremely aggressive and will decimate anything it can catch, including other Soapdish crabs of equal or  greater size. does not play well with others. I've even heard of one wasting an Oscar. <Have seen this sort, level of "aggression"> oh, why might a fiddler crab in similar tank conditions up and die for no obvious reason. <Is a brackish water animal...> a not too old/big male that seemed to be thriving was fine one day and upside down dead by the filter the next. he shares the tank with 2 females and one other male which doesn't currently even have its large claw. I don't suspect foul play, I am afraid there is something wrong with the water or something. the tank has been in operation for at least 6 months and has a good filter. I've heard a terrible rumor about fiddler crabs just dying after a while in fresh (not brackish) water but I've had a lot of these wonderful, mostly peaceful crabs and this is a brand new occurrence. any thoughts?  might the same thing happen to Carl? <What is the make-up of your source water? You may have hard, alkaline water that "works" for both these species> just one more thing, I promise. I employ a multitude of ghost shrimp as janitors and I read on your website that it was easy to breed them. that is very exciting to me, please tell me more! I am so glad I found your website, I hope you can give me a few pointers. thanks, Scott <Use your computer search tool/s... much written on Ghost Shrimp. Bob Fenner>
Re: Soapdish crab
hello again! Carl has molted! about a week after starting the iodine treatments, Carl (Thai freshwater- Soapdish crab) molted.  could this be directly related to the addition of iodine? <Yes> unfortunately,  it did not go well for the big guy and he lost a leg and his larger pincher. <Evidence of? Likely a lack of biomineral (calcium) and alkalinity... provided in foods, water...> the next couple days were very tough for both of us, as he just sat there and twitched and I was terrified that he wasn't going to make it.  the next day I came home from work to find him on his back and motionless.  I nearly lost my mind with grief until I noticed his mouth apparatus was moving. I very gently touched the tip of his claw and to my great relief he sprung to life, trying desperately to flip over.  the poor guy just didn't have the strength! he was still very soft, so I decided to let him be rather than possibly injuring him by flipping him over.  after a couple more days he eventually started to consume his exoskeleton and move around the tank.  Carl's gonna be ok!  whew! now for the questions: I've noticed that since the molt his carapace and claw look very strange- its a very dull tan-gray and none of his normal patterns, like the "H"  on his back, are visible. it just looks very worn, or something. I know crabs will sometimes come out of a molt a different color, but the way Carl's shell looks makes me think its related to his traumatic molt. any ideas? <Either lack of nutrition, water quality... or will develop color, pattern in time> Also, is it possible to over dose them on iodine? <Oh yes> should I add the drop only when I do a complete water change or anytime I replace water that has evaporated? <Best to do with (weekly) water change regimens> keep in mind I have a 10 gallon filter in about 4 gallons of water, does that make a difference as to how fast the iodine is getting used up? <Yes> One more thing: I really want to change my crab tanks to brackish but I have read that once crabs are in freshwater for so long, they cannot be switched to brackish. is this true? <Not so. Bob Fenner> thank you in advance. Scott

Injured Red Claw Crab Hi, firstly thanks for such a great website! The information here is comprehensive yet easy to understand. Unfortunately I have a problem with my Sesarma bidens crab. The other night whilst cleaning out the tank I did not notice the crab (Colin) burrowed under a plant, as he is almost always hiding under an ornament on the other side of the tank during the day (or breathing sitting out of the water on top of it).  He just recently molted (about a week ago) so I thought I would leave him under the rock and clean the tank around him. Well I dumped the plant in a bucket (with Colin underneath it) and proceeded to vacuum out the gravel and remove other ornaments to the bucket. It was only when putting the ornaments back that I noticed Colin at the bottom of the bucket on his back... I immediately picked him up and put him in the tank but he didn't move, I put lots of little bits of food in front of him and left him for the night thinking the worst.  When I came back in the morning he was on his back again but when I went to lift him out of the tank assuming he was dead he started moving his legs frantically, anyway I righted him but noticed that 5 of his legs were not working as well as one claw (I think they must have been broken in the accident) he was attempting to move around but the legs were preventing him, I left him for the day came back and he still had not moved despite attempting to with his working legs, so I amputated 3 of the legs at the base (not the claw) he is now a lot more mobile however he is unbalanced due to missing 2 back legs (resulting in him overturning and not being able to right himself frequently/a few times a day).  I have also since noticed that one side of his mouth is not working (i.e. the exterior movable parts of his mouth that he uses to clean his eyes) he can still move it a little but cannot properly function.  My question is: Is there anything I can do for Colin? I am aware that crabs can regenerate limbs during a molt but has he just sustained too much damage? <I hope not> My main concern is his mouth as I cannot see whether he is eating properly. Would it be kinder to just kill him now or try to aid his recovery?  <I would not euthanize this animal. It may well recover> It has been three days since the accident and he is still defending his food against the fish (a few platies) but I cannot establish if he is eating the food or whether the platies are eventually managing to take it all. In this situation could a premature molt occur or could he partially grow back before a molt? <Not before, but might molt again sooner, shrink in body size> I really don't want to have to kill him but equally I do not want to prolong his life if he is suffering with very little chance of recovery. He is in a 5 gallon tank with 0 ammonia, 0 nitrites, 20ppm nitrate, just over 1 tbsp. of salt per gallon and I am lifting him out of the tank daily for a few minutes to allow him access to air. pH is 6.6 (low I know but I added dolomite to the filter on the day of to raise it so hopefully that will start to take effect). Should I dose with Iodine? <Yes, I would> Sorry for the long question but I am very concerned about him.  Thanks, Chris <Do take care to maintain good, consistent water quality, assure this animal is getting food. Could take weeks to a few months, but may well be fine. Bob Fenner> 

Freshwater Invertebrates, ID? Hey guys I am trying to ID a crab that is appearing more and more frequently in Australian stores. It has been incorrectly identified by several stores as Amarinus lacustris (Freshwater spider crab). I suspect the supplier is keeping this myth alive *lol Anyway, the crab in question is often referred to as a "brown backed crab". Orange/brown body with a chocolate brown H symbol on its shell. claws of equal size and quite heavy set, not long/slender. It seems to get to about 2" shell width. I would LOVE to know the scientific name for this little beauty, as although I am sure I could keep it happy using general crab knowledge, it would be nice to know its specifics. Sincerely, Abbey AKA Callatya <Hey there, sorry it took me forever!  http://www.fishprofiles.net/files/~adam/tanks.htm  Right down the bottom of that page is a front-on view of that crab. I asked a large pet store and they said they are buying them under the name Holthuisana agassizi.  I cannot for the life of me find any reference to this species online, so I thought maybe, just maybe, you guys might have more references that I have access too. Thanks for your help! < I have seen this crab at wholesalers referred to as "red clawed crabs" from Asia. Try looking in the internet under that name to see if you can find more info. -Chuck> 

Red Claw Crab <Hi Anthony, MacL here. The only red claw crab I know of is actually a brackish crab often sold for freshwater. Is this what you have?> I purchased a red claw crab from a local Fish store about 2 weeks ago. I believe the crab is a female due to the very small claws.  Anyway, recently she has had her abdomen hanging open. <Maybe releasing eggs?> I figure she was getting ready to molt, but she hasn't done anything for 2 days now. She has already molted once since we have had her and it didn't take long.  She has plenty of different kinds of food.  Also these past 2 days she is flipping herself over on her back. <Not a really good sign.>  Can you tell me what is wrong? <I'm just guessing here but I think you probably have her in fresh water and she needs some salt. I also think it might be a difference in PH as well.>  I have searched through the internet, but cannot find any information on Red Claw Crabs.  <I did a search on Google and came up with tons of thing on them.  You might try www.google.com> Thank you for your time and patience. <Anthony you might do the research on them and decide if it needs to be in brackish water or not and make a decision from there.> Anthony <An excellent site re this species: http://wrongcrowd.com/aquaria/crab/ RMF>

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