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FAQs on Freshwater Crabs 2

FAQs on FW Crabs by Species: Halloween Crabs, Panther Crabs, Vampire Crabs (Geosesarma Bicolor), "Other" real and purported Freshwater Crab species,

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,

Parathelphusa pantherina Biotope Aquarium      6/15/14
Hello, I've emailed you before and have had great service from you and you seem to know your stuff, so I thought I might run a few things by you again to see what you thought.
<Fire away.>
I am planning a biotope aquarium based on Lake Matano with the prime species being Parathelphusa pantherina (Panther Crab). I have had some of these before and have learned quite a bit and hope to succeed in breeding them this time.
Last time I kept them, one was a female and released her pheromones in a too small of an aquarium and drove the males crazy. Needless to say, I found her limbless and she didn't make it.
<Some potential to separate them is surely a good idea, e.g., with egg crate. Do read on similar problems with cichlids.>
Anyways, I plan to keep them in a DIY acrylic aquarium measuring approximately 74 inches by 52 inches by 18 to 20 inches tall. I plan on housing three trios in this aquarium (trio = one male, two females). I've
done the math and this should leave plenty of space for them.
<Let's hope the crabs understand the maths too. Seriously, the hobby's track record of keeping amphibious crabs together is very poor. Many were shipped in soap boxes once upon a time, singly, so they couldn't interact with any others. During moulting they are all especially vulnerable, because a moulting crab is defenceless and viewed as an easy meal for any other crab. In the wild moulting crabs use deep burrows or something else to hide in.>
It's recommended you have one square foot of surface area to each inch of crab, so for these crabs being three inches, they need approximately three square feet of area each.
<While this recommendation sounds good, I suspect surface area is less important than topology. A crab isn't going to ignore one that's an inch outside "it's" square foot. So while providing space is important, you
probably also need rockwork, caves, 3D climbing structures and space above the waterline. This latter is important. A crab feeding on land can't see one below the waterline, and vice versa. I'm no expert on crab behaviour, but I'd also suspect they have different sets of behaviours used above and below the waterline because the predators, resources and stresses will be different.>
In the aquarium I have planned, this leaves just enough room for all nine crabs. I plan to replicate Lake Matano as much as possible including aquarium inhabitants but as of yet have not researched what other species of aquatic life are endemic/native to the lake, but I am open to suggestions (fish spp, shrimp spp, maybe some good substitutes).
<Snails and shrimps are definitely crab food, so a non-runner. Fish will be highly risky, as ever with crabs. While these crabs aren't fish predators, they are fish scavengers, and if a crab comes across a sleepy fish or manages to corner one... we'll, that fish becomes dinner. One crab might be tenable with a bunch of (initially inexpensive) fast moving midwater species along the lines of big barbs, but the more crabs, the less peace the fish will have. I think you're trying to do too much here. Breeding will require one set of criteria: potential to isolate "picked on" individuals; easy cleaning to reduce bacterial and fungal infections of eggs; countless hiding places to break up lines of sight; and some degree of flexibility so you can change the tank decor as needed when the unexpected happens. A biotope aquarium is designed for aesthetics, usually as a caricature of a particular place or habitat. That tends to force you to decorate an aquarium in a way that is less easy to maintain, rearrange or divide up with egg crate.>
I hope to create as much of a fully sustaining ecosystem as possible in all future aquariums but will be prepared to intervene if necessary.
<Do read "Dynamic Aquaria" if at all possible; the science behind microcosms that sustain themselves has been done, is extremely complex, and for home hobbyists, overwhelming. That said, if you're prepared for the extra cost needed for a biotope aquarium (e.g., in optimising plant growth) and stock the tank very lightly (understocking is virtually essential) then you can create tanks that more or less manage themselves in some regards, such as algae control and even population if the fish or shrimps breed.>
I know you recommend housing crabs alone,
<With good reason.>
but I feel confident about what I am embarking on.
<Which is fine. But have a Plan B.>
I plan to use driftwood with some sticking out of the water so the crabs can climb on them if they want, some sort of sand (open to suggestions)
that is natural-like, and rocks (what kinds of rocks are in Lake Matano?).
<No idea! But use neutral rocks regardless, such as granite or slate since the water isn't especially hard.>
I am open to suggestions on my setup. I will not be putting anything near the edges for them to climb out of the aquarium (to help prevent fatalities).
I will have a sump with heaters and plants for filtration.
<How will you keep the crabs out of the sump?>
A drip system will continuously cycle my aquarium to help reduce concentrations of hormones and prevent need of water changes (water will be dripped into aquarium and excess overflowed out through the sump).
<Unless the hormones are diluted with fresh water, and old water continually leaves your aquarium (and sump) for the drains, hormone levels in the tank will not go down. Honestly, I suspect managing crab behaviour this way is dubious. Indeed, I can't find anything on Google Scholar about Parathelphusa hormones. Is this something brewed on the Internet or some cutting-edge scientific research? All the crustaceans I've ever worked with have been visually-oriented animals that use body postures, claw waving and so on to communicate. So while Panther Crabs aren't nearly as lethal as, say, Soap Box/Rainbow Crabs, I'd still be focusing on ensuring a complex, 3D habitat with lots of objects breaking lines of sight, as well as plenty of suitable caves and burrows. Might end up looking less like the Lake
Matano, but would nonetheless be more suitable for keeping crabs in numbers greater than 1 specimen.>
Any suggestions? I appreciate you answering my questions and giving me advice on how this may or may not work out. Have an awesome day!
<Most welcome, Neale.>
Re: Parathelphusa pantherina Biotope Aquarium      6/19/14

So, I've decided to play it safe and focus on breeding the crabs first. I was reading up on a few things and came across your article about the freshwater deep sand bed. I was wondering if it'd be possible for me to set up one of these in a 10 gallon aquarium with one crab?
<Do you mean Deirdre Kylie's article?
Doable, yes; worthwhile, debatable. A 10-gallon tank isn't especially large; the standard US version has a depth of 12 inches (about 30 cm).
Since you need 3 inches (at least) for the DSB, that leaves you relatively little for the water. It would certainly be fun trying, but think about any potential compromises you might have to make. I will also observe that crabs are almost always deposit feeders to some degree, which means they sift mud and eat any organic material they find. That's great in the wild, but will make a full-featured DSB somewhat less easy to create because things like worms and micro-crustaceans are going to be eaten.>
I plan on putting one crab in a 10 gallon with a 10 gallon sump.
<Ah now, the DSB in the sump *would* work, and could work great.>
The 10 aquariums would be connected to each other via an overflow in each aquarium.
<Sounds good.>
I may put in a water bridge, but just thought of this as I was typing this, so I'm still undecided on this. Anyways, what are your thoughts on the deep sand bed? Will the crabs burrow too much?
<Not sure these are deep burrowing crabs, and don't look like them, but most crabs do usually move about the top layer of mud as indicated above. I have no idea how much movement this species is likely to carry out, but I'd be aware of the possibility.>
Should I just have it in the sump? I plan on a three inch deep substrate for the DSB, and in case the crabs want to burrow. Thank you for your time.
Have an awesome day!
<Breeding projects are most easily done in the cleanest possible tanks for various reasons including minimising opportunistic bacteria and making it easy to see eggs/fry. If this was me, and breeding was my goal, I'd probably look at plain tanks, sponge filters (great for aufwuchs growth) and easy to clean climbing surfaces for the crabs. But if breeding is a welcome spin-off rather than the prime goal, then a "freshwater reef tank" project with the focus on microbial life could be very worthwhile, and might provide opportunistically useful food and niches for crab eggs/zoea.
I think you will need to consult Google Scholar to find out whether Parathelphusa spp have a marine larval stage; I do not know if they do (many amphibious crabs do) and that may be a complicating factor that
requires collecting eggs, transferring to brackish then salt water, and rearing accordingly. Has been done, rarely, in the case of some freshwater Gobies and Amano Shrimps, but obviously a major project. 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.>

Panther Crab (Parathelphusa pantherina) color forms?     11/1/12
Hey again. I read something and saw a few pictures of these crabs claiming to be different color forms. They mentioned red, purple, brown, and white clawed color forms in addition to the most commonly seen leopard spot colour form. Is this true?
<No idea, to be honest!>
Can they be different color forms of the same species?
<Or a closely related set of species.>
Are these actually the same species or are they different species? If these are the same species just different color forms, I may try to locate all of them and breed them all.
<Nice that you have a goal! But to avoid disappointment, do consider trying out something simpler, like crayfish, so that you understand the basics.>
Thanks for answering my questions!
<Most welcome. Cheers, Neale.>
Re: Calcium Supplements for Panther Crabs?     11/1/12

I know you told me about the cooked unshelled shrimp commonly used for human consumption, but wanted to know a couple things. I've heard you can also feed egg shells and cuttlebones to crustaceans to help them get the calcium they need. Is this true?
<Potentially, but it depends if your crab will eat them. By themselves they don't sound very appetizing!>
Which type of cuttlebone should I use, if any? Also, how can I help ease the moulting process to help ensure proper moulting and survival?
<Use marine aquarium iodine supplement, at 50% the dose stated on the bottle.>
How long does this normally take (moulting and hardening of new shell)?
<Varies dramatically with age. Young crabs may moult once a month, while older specimens may essentially stop moulting altogether, and their shells often look very tatty and encrusted with algae.>
Thanks for everything!
<Real good, Neale.>
Re: Calcium Supplements for Panther Crabs?      11/2/12

Okay. One more question. After a crab moults, how long does it take for their new shell to harden?
<Hours, couple days, depending on species, temperature, diet, calcium availability.>
Essentially, how long should I wait until I start worrying about if the crab is alive or not?
<Anything more than a week would be worrying. But keep crabs singly, give them iodine, let them eat calcium-rich foods, and moulting should happen without problems. It's when people either ignore their mineral nutrition and/or keep them in groups (or with fish) that moults fail. Cheers, Neale.>
Re: Calcium Supplements for Panther Crabs?

I'm getting a male and a female Panther Crab and am planning on housing them together because I heard the male impregnates the females when she moults. Is this true?
<Yes; or at least, is standard for crabs generally.>
Should I separate them when they moult just in case or when she isn't mature?
<Sounds wise.>
I am going to put them in a 20 gallon long which I've heard is able to house two female and one male Panther Crabs.
<Hmm… I wouldn't bank on this, but I don't know for sure it won't work. It's a case of "suck it and see".>
<Welcome, 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.>

Halloween Moon Crab - Gecarcinus quadratus 12/8/11
I have two g. quadratus crabs - purchased both 12/2010. Keep both together in 20 gal. long with coco fiber substrate, hermit crab sand pile, coco huts/logs to hid in and live plants. Keep moving water fountain and use mister for humidity. Tank temp. ranges 68 - 85, depending on local weather. Humidity at 75% and up. Food offerings are fresh fruit, veggies, hermit crab "cookies", live crickets, shrimp, cooked chicken. Water is declor treated. I have recently noticed that one of the crabs has stopped eating and is sluggish. He still moves around, however, he is not as active.
<Coming up to moulting perhaps?>
Also, he dropped one of his rear legs that seemed damaged at the mid joint.
He is usually the more aggressive crab of the two. What are signs of molting?
<Typically the moult comes off all at once, rather than a pair of legs at a time. In any event, moulting crabs drink a lot, which puffs up their new shell, and then go hide somewhere. Immediately before moulting crabs can feel sloshy if shaken.>
Neither crab has molted in my care. I have also noticed that the crab is taking on more water and that the whitish material under his shell on his backside and alongside his legs is extremely engorged.
Are those his gills?
<Probably not. The gills are inside the body, underneath the "apron" part of the shell.>
The other day I found him upside down in the fountain. Thought he has died. When I picked him up, he pinched me and spit water at me (why do they spit water?).
<They're cross?>
I could feel water moving inside his shell. I placed him back in tank and now heat tank with 2 75W "moon" bulbs and covered his side of tank with paper for privacy. Crabs are located in very open area. Do I need to supplement with iodine?
<Well, tricky to do with terrestrial crabs. You can get iodine-enriched tablet foods for crabs and these would be good. Otherwise, marine algae is good, e.g., Sushi Nor.>
Should I be adding marine salt to water?
<Not with this species, no, it's a freshwater one I believe. If you wanted to be super-safe, you'd offer one pool of freshwater and one pool of brackish water, and let the crabs choose what they want.>
Have I made this crab sick with improper care?
<Probably not, but do be aware the other crab will likely kill, eat the moulting one.>
Please help.
<Cheers, Neale.>
Re: Halloween Moon Crab - Gecarcinus quadratus 12/8/11

Thank you for such prompt response. I will make arrangements to separate the crabs until this is figured out.
<Sounds wise.>
I will keep the tank dark and limit activities with the potentially moulting crab to just water changes and food offerings. I would think that this will reduce his stress so that he can accomplish a successful moult.
<I agree.>
I will still keep misting with warm water to keep up humidity.
<Good idea.>
I took the fountain out and just have a pool of water (so in case he falls over into fountain, he can flip over again so he doesn't drown). I also have noticed last week that instead of brown poop logs, he was eliminating some sort of greenish-whitish watery goo out of the little chute under his mouthparts.
Is there any other signs of moulting that I should be on the lookout for versus having a sick crab..... I will be relieved when he is back to his crabby self again.
<Honestly, there's little to no understanding of crab health, so all you can really do is ensure the right environment, a good diet, and hope for the best. If the crab does get sick, there's nothing at all you can do. We simply don't know enough (anything!) about crustacean healthcare. Moulting crabs tend to be shy and retiring, for obvious reasons, and so we as pet owners see very little of what's happening. But there are not usually odd secretions, so the green goo sounds odd. On the other hand, he may simply have eaten something disagreeable.>
Thanks again,
<You're welcome. Good luck, 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.>

Panther Crabs! 6/29/11
Hey there folks! As always, I have a few questions if you don't mind helping me out with! I've looked far and wide for a completely fresh water dependant crab! Parathelphusa panthernia
<Parathelphusa pantherina.>
appears to be just what I've been looking for but is it all of what little I've read it to be?
so here we go!
#1 T or F - I've read it does not require a land portion for its habitat and can purely stay in a fully filled aquarium.
<More or less. They will crawl out onto floating plants and above-the-water wood or stones, but only for short periods. So provided there's at least a bit of land, even if that's just the top of an internal canister filter it can perch on, it'll be happy. Conversely, yes, it can climb, and yes, it will escape from an aquarium given the chance.>
#2 T or F - It IS completely Fresh water, NO BRACKISH or full marine needed.
<Is indeed freshwater. Hard, alkaline freshwater.>
#3 T or F - They grow to a decent size, 3 inch on just the shell, but with legs around 5 inch, and thus the minimum tank size is 5 gallons per crab (2 for a 10 gallon)
<Two will kill each other. One in an 10 gallon tank would be fine. If you get one male and two or more females, allowing 25-30 gallons for the first trio, and another 5-10 gallons per extra female, you should be okay. But two males will fight.>
#4 T or F - They will eat or uproot plants, even the toughest leaves are not safe from their grasp!
<Yes, they are omnivores and view plants as food. But tough plants like Java fern should be okay, and fast-growing plants like Hygrophila and Indian fern should keep up with any damage. Just don't expect to keep one in an Amano tank!>
#5 T or F - They WILL eat any sort of dwarf crayfish, shrimp or fish that it can catch or get a hold of somehow.
<Yes, they are omnivores and view any fish, shrimp or crayfish as potential food.>
Anyone with knowledge on these crabs PLEASE help with these T or F questions! I have a 10 gallon all ready and waiting for either these panther crabs (preferred), dwarf crays, or Aegla sp. argentina (if I could even find any), my tank is a low light set up so it has crypts Anubias and soon to be mosses, so hardy plants for that matter..
I thought you would enjoy a little T or F trivia to change the pace of your email reading haha! -Shovelman (AKA-John)
<Certainly makes a change! Nice animals, by the way. Cheers, Neale.>
Re: Panther Crabs! 6/29/11
Thanks Neale! You don't by chance happen to be on tropical fish forums as well? I always see "Neale" replying to many questions and concerns in the oddballs section most frequently?
<Yep, that would be me! Cheers, Neale.>

Panther Crab, care 1/17/11
I recently bought a Panther Crab for my aquarium and I can't find any information what so ever on how to take care of them.
<I assume this is Parathelphusa pantherina.>
My aquarium is relatively small... and they act quite strangely. The only things I could find about them is that they like scavenging at night and are known for attacking slow and big fish, though I guess you could say that of most crabs.
<Yes, though like all crabs their diet is really very varied, with things like whole lancefish and unshelled shrimp being particularly important as sources of calcium. Use marine aquarium salt as stated on the package, but at a half dose. This will ensure safe moulting; without extra iodine, many crustaceans have problems moulting. Also offer algae wafers and soft greens such as cucumber slices.>
This is not anything really important as I assume you are getting many other e-mails of much more importance. If you have the time though and you know anything I should be doing in specific to help these guys please respond.
<Standard vivarium set up required, though Parathelphusa pantherina spends less time on land that most, so a few bogwood branches above the waterline would be acceptable if space was limited. Hard, basic water is important -- 10+ degrees dH, pH 7.5-8.5. Water temperature middling, 25 C/77 F is fine.
As with other crabs they're territorial and need hiding places when resting and moulting; hollow ornaments and PVC tubes are ideal. Don't keep more than one male per vivarium, and even females are likely to be molested by the male if the tank is too small. Best kept singly, really. Your 12 gallon tank should be okay for a single specimen, but that assumes you keep it clean and perform regular water changes. Keep the tank securely covered --
all crabs are very good at escaping!>
Extra Information: I'm not a aquarium expert so feel free to correct me...
My aquarium is only about 12 gallons and doesn't have many hiding places. I have about 6-7 Neon Tetras in my Aquarium and 5 of this other species of fish.. can't remember their exact name but they are slightly smaller then the Tetras. Are they in danger?
<Yes; they're crab food for one thing. Also, the crabs need hard, basic water unlike the Neons that want soft, acidic water. So not good companions. All crabs are best kept -- in fact must be kept -- on their own. Cheers, Neale.>

Re: Panther Crab 1/18/11

Wow! Lots of helpful information, thanks for the quick respond too I appreciate it a lot! One last question.. if you don't mind. I recently noticed this small... algae looking thing growing on a small log I put in my aquarium. It is very dark grey in color and doubled in size this week (Though it is still very small) It kind of looks like a sea anemone but dark grey. It seems as if I accidently dropped a fur ball into the aquarium and it stuck to a log and decided to start growing! I would type this on Google to figure out what it is but I don't think "Grey growing sea anemone looking thing" would come up with many results. If you heard of this kind of thing before it would be nice to know what it is, thanks.
<Without a photo, hard to say. Likely algae, but possibly fungus, the latter usually colourless to grey. Algae can be a variety of colours. If you send photos, remember, keep them no larger than 500 KB, and if necessary, use an application like iPhoto to reduce them.>
Also one last "extra information" I forgot to add in my last message.. : I also have about maybe 5 Cray fish in my aquarium. Very small crayfish.. I guess they are possibly those unshelled ones you were speaking of.
<Hmm'¦ not really. While a crab *might* eat crayfish, you'll likely find standard unshelled shrimp or krill from the pet store better value. Buy frozen and defrost as required. Use regularly but not to excess because the vitamin content of shrimp isn't good. Balance shrimp against white fish fillet (ideally, tilapia) and algae wafers.>
It kind of seems like right now I have a huge feeding ground for my crab, and its food is everything in my aquarium. Problem is that I love my Panther Crab and that crabs are my favorite type of aquarium animal I could hope for, but I don't want to just catch every single fish in my aquarium and crayfish just so my crab can have some peace. What is my best option?
<Crabs require their own tanks. Don't delude yourself into thinking otherwise. Small fish/crayfish will be eaten by the crab, while bigger fish and crayfish can, will damage the crab during its moult. Fish, crayfish, and crabs all need their own tanks. There isn't a magic solution to this one. Cheers, Neale.>
Re: Panther Crab, mortuus est 1/24/11

Well, I don't have the photo, but something more important than the small little ball has arisen! My panther crab.. died. I read that they can live up to five years somewhere,
<Not even sure they've been traded for 5 years. But yes, amphibious and land crabs do indeed have this sort of lifespan under good conditions. They rarely live this long though because they're usually kept in the wrong conditions, e.g., in an aquarium.>
and at first I thought he was just sleeping. Because he couldn't of died in a position as strange as this, he died on his side, half of his legs are holding him in the air on one side while the other half of his legs face towards the surface. I thought he was just messing around until I noticed he's been like this for three days now and won't respond to anything that moves near him. I don't know what could've cut down his life so shortly especially since I don't think a small Neon Tetra could've killed him!
<Indeed not, but an aquarium designed for Neons will be inhospitable to Panther Crabs, which are amphibious.>
He had some kind of strange... white.. don't know what else to call it but, strange white object growing out of the right side of his body.
<Fungus most probably. Post-mortem.>
I thought it might of been a parasite or he could've been sick. Could this of been the cause of his death?
Or is he just molting.. in a strange position for a really long time.
<No; moulting doesn't make the crab inactive, just shy. It withdraws to its burrow, and then moults quite quickly, within a couple of hours usually. It re-emerges once the new skeleton has hardened off, typically within 24 hours. Crabs in captivity need dosing with iodine used in reef tanks, though only at 50% the quoted dose on the bottle.>
<Cheers, Neale.>

Freshwater Crab... some reading now! 1/5/11
I have a freshwater male crab in a ten gallon tank.
<Almost certainly neither a freshwater crab nor an aquatic crab.
Is this Perisesarma bidens by any chance?>
Along with the crab I have a sucker fish,
<Needs 55 gallons, assuming this is Pterygoplichthys pardalis.>
dragon fish
<Gobioides spp.? This is a big, brackish water fish that will die if you keep it in freshwater; read here:
and a black fin shark.
<Is this Sciades seemanni? A schooling brackish to marine catfish; read here:
This evening I noticed that the large claw and one leg was missing, they look like they were ripped out. I was wondering if the crab is suppose to remove its limb when molting? Or is there anything else that could have happened that I am unaware of. The fish have lived in the tank for a while now and been very harmonious, or so I thought.
Thanks Melissa B
<Melissa, if these animals are what I think they are, you have a crazy collection of livestock in a tank far too small for them and filled with the wrong water for most of them. Sooner of later they're all going to die.
Read about the animals you've bought -- seemingly at random! -- and rehome them. That they've lived together for a short while doesn't mean much of anything, so you need to get real about these poor animals and provide them with the conditions they need. They're all fun animals in the right tanks, and I'm happy to provide further information should you need it. 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.>

Please Help 11/7/10
Hi, Thank you for making this link available so that all us people who have question can have them answered.
I just recently got into raising vampire crabs. I have two males in a 10 gallon half land half water tank with a couple fiddlers (they get along well).
<Tenuously... the Crabs will eat the Fiddlers in time>
A few days ago I bought a female to join my two males but three days later I found her dead. The two males seem fine but I noticed tiny white worms in the water.
I'm wondering if they came from her and that's why she died and if that's the case I need to know what kind of monsters I'm dealing with and how to kill them before they get my others. I've been searching for hours but haven't found any clear answers, especially for the vampire crabs. I would greatly appreciate a good web link
<For worm ID?>
so I can gain more knowledge on what kind of creatures can infest and or kill my new little pets.
<Likely cumulative stress... there are plenty of sites, info. on the Net re this Geodesarma...>
Patiently awaiting your response. Thanks a bunch.
<The fiddlers need to live elsewhere... Bob Fenner>

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)>

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