FAQs on Freshwater, Terrestrial
Related Articles: Fresh to Brackish
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, Freshwater Crabs 2, & FAQs on: FW Crab Identification, FW Crab Behavior, FW Crab Compatibility, FW Crab Selection, 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, & Crayfish FAQs, Crayfish 2, Crayfish ID, Crayfish Behavior, Crayfish Compatibility, Crayfish Selection, Crayfish Systems, Crayfish Feeding, Crayfish Disease, Crayfish Reproduction,
Calcium in Crab & Shrimp Tanks 6/2/16
I keep a few crustaceans (Panther crabs, Rainbows crabs, Geosesarma
crabs, Crayfish and Cherry Shrimp). I know that calcium is important for
the proper development of their shells. I have looked all over the net
and can't find any definitive information on how much calcium and how
often it's needed, so I'm hoping you can help.
I bought some small calcium tablets (1" long by .5" wide), but I haven't
put them in the tanks yet. I need to know how often I should be giving
my crustaceans calcium and how much. So far they've been doing good but
I want to make sure they have the best care possible.
Any help is much appreciated. Thank you.
<As with humans, it's the "bio-available" Ca that is important; and for
freshwater organisms this takes the form of both dissolved and
macro-sources. Unless you have a Calcium concentration test assay, I'd
rely on "hardness" as a measure here; and aim for "medium hardness"
(measured in various ways:
AND I would use the small calcium tablets you mention (or softer sea
shells, cuttle bone) as an exogenous source these animals can/may pick
Parathelphusa pantherina Biotope Aquarium
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.
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).
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
<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
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
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
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
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.
Fully Aquatic Freshwater Crab?
Well, I'm using a different e-mail but I wrote you awhile ago,
twice. (I forgot the address and password of the e-mail.) Both times it
involved things in my aquarium dying.. (First my Crab, then all my Neon
I recently re-visited the place I buy my crabs, shrimps, and fishes
from. (I don't buy fish anymore after that Neon Tetra incident.)
After you told me that crabs should have land I noticed that the crabs
I buy have only water in their buying tank and no land. I decided to
buy another and pay a lot closer attention to them. The new one I
bought is a lot smaller than the old one, but still the same species.
Are there any fully aquatic freshwater Crabs?
<Mmm; none that I'm aware of, no>
If so, is mine? I don't know the scientific name for it but I can
describe him.. it looks a lot like the female Flower Crab. (Portunus
<... this isn't a freshwater animal: http://en.wikipedia.org/wiki/Portunus_pelagicus>
Since I didn't see a single male among them, or one that looks like
a male, I can only assume that the crab is not that species.
It has mainly a light brown color with many small black dots around its
body. It has an orange color under its claws and the back of its shell
is mainly dominated by those black dots. Its eyes are completely black,
its legs are orange, its underbelly is white, and if you were to
stretch its legs from side to side and measure it across it would
probably be 1 and a half to 2 inches. It's quite shy as whenever I
walk by it will run for cover immediately while my other Crayfish just
sit there unwavered. It seems very passive and it won't kill
anything (At least from what I've seen.) It also likes digging up
the ground and creating ditches. It eats all the plants I buy (over a
span of around one plant per 2 weeks) One thing I haven't mentioned
about the previous incidents is that my crayfish are not the ones with
claws. They have no claws and are very, very small. (Around a fourth of
an inch!) If you can identify this Crab, what should I do to ensure it
lives well and is it fully aquatic?
<See the Net>
Sorry for it being so long but I have one last question... A really
long time ago when I was first setting up my aquarium and I finished
the starting group of animals I got were: Around 4 mini-Crayfish and
one that was about an inch in size, was bright Orange and had claws. It
seemed to eat all the crayfish though I never caught it I always
noticed the numbers of my Crayfish decreasing. I later asked the owner
if these ate those mini-Crayfish and he said they didn't though all
my crayfish seemed to die in the same area. (Feeding Ground?)
Eventually it passed on and I wanted to know he was responsible for the
deaths of my other Crayfish or if there could be another reason.
<Could be... Read here:
and the linked files above>
Really sorry about all these incidents that talk about my crayfish/fish
dying, must make me sound like a terrible 'aquariumist'.
<A developing one. Bob Fenner>
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
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
<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
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,
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.>
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
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
<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
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).
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.>
Question about my rainbow crab 6/21/10
Hey, I`ve owned my rainbow crab `Peaches` for 4months now, he's so
<Cardisoma armatum, I assume? There are, unfortunately, other crabs
sold under the "rainbow crab" name.>
I keep him with loads and loads of sand that he happily burrows in and
a plant pot for hiding and a lunchbox full of normal tap water.
But I`ve been reading a lot about having to treat the water or use
`saltwater`, I love this little guy to pieces and would appreciate any
professional help you can give me with his upbringing.
<Actually, while these crabs do come from coastal regions of West
Africa, they don't appear to need brackish water to do well, though
they may well need brackish or saltwater for breeding. The use of a
iodine supplement in his bathing water, at one-half the dose
recommended for marine tanks, would actually be much more useful. With
that said, if you wanted to (also) add 2-3 grammes of marine aquarium
salt mix per litre
of water, that wouldn't do any harm, and may even do some
He seems quite happy though but I really don't want to risk anything
with looking after him. Any help would be much appreciated :-) many
unknown crab, terr. 4/19/09
I hope you can shed some light on my current dilemma and give me
a few pointers and how to take care of this beautiful crab I
rescued today. I received a call from a friend that works at
PetCo. He says "I have this awesome crab that someone just
dropped off in a bucket and have no idea what to do with it. Do
you want it?" Of course being the lover of all God's
creatures that I am, I said "Yes". Keep in mind, I have
zero idea what I have or how to care for it.
<Usually not difficult with crabs. They need something very
similar to what you'd offer frogs or newts: shallow pool of
water to bathe in; lots of damp moss and rock above the water; a
source of warmth; and an enclosure with a tight lid so they
can't escape. Virtually none of the species in the trade is
aquatic, and all will spend most of the time on land.>
I have six fish tanks, all freshwater and no crab experience. I
have searched the web to find not much info. It looks a lot like
a soap dish crab, same basic shape, but this one I have is so
awesome in color. Not
plain reddish/brown like the pics I have seen online. One call I
made said possibly a Thai Devil crab. I am attaching a photo. It
is female, I do know that much.
<Very likely a Cardisoma species of some sort, so basically
similar to the Soap Dish Crab in terms of being terrestrial,
largely herbivorous, and highly aggressive.>
She is currently in a 20g tall tank with a mix of gravel and
<It's a land crab. You can easily tell land crabs from
Land crabs have tall, boxy bodies. They have that shape to make
space for the structures that effectively function as their
lungs. By contrast underwater crabs are usually more flattened so
they are streamlined and not pushed over by water currents.
Another good clue is the back pair of legs; on underwater crabs
these are usually flattened into swimmerets, basically paddled;
on land crabs they are pointed, just like the walking
I have a submersible filter running and I have some rocks she can
climb out onto so that she isn't constantly submerged and
have given a healthy dose of aquarium salt.
<Not a brackish water species, so far as I know. I'd
certainly not keep her in an aquatic environment. Honestly,
she's a land animal.>
I read in a several of the forums that I may need to get iodine
supplements and some different salts. Does she need a heater?
Anyway, so far she seems to prefer being under the surface for
the most part. Every now and again she pops up out of the water
just far enough to inhale through her "nose" and
immediately exhales through her back side. I want to absolutely
do right by her as she has obviously had a decent life so far.
Can't imagine someone just bailing on her as they did today.
She is fairly good sized with her body being about 2.5"
across. Many thanks in advance for whatever info you can help me
<Read up on Cardisoma species, and keep in the same basic way.
These animals like damp, but terrestrial, habitats and feed
extensively on soft fruits, dead animals, etc. Couple of inches
of filtered water ample. Iodine supplements are useful. Cheers,
Re: unknown crab 4/19/09
Thank you so much for the super fast reply.
<Happy to help.>
Beautiful isn't she?
We are just amazed at her colors. I am real concerned about
taking care of this crab. Ok, just a couple more questions. Is
the 20 tall big enough?
<Should be ample, especially if you use lots of bogwood or
whatever to create places to climb.>
I have a 55g that has a crack in the bottom that is not being
used. Or is that overkill?
<I'm sure the crab would love that tank, but why not keep
things simple and inexpensive for now?>
Is the gravel and crushed coral ok or should I get a bunch of
<Either. These animals aren't at all fussy. Wild animals
burrow into mud.
They burrow into the mud along river banks a lot, so if they can
dig, that's great. Here are the things that matter: Firstly,
that you can clean the tank out easily. Some folks find
"disposable" media like coconut fibre
the ideal in this regard, simply cleaning it all out before it
Other folks prefer substrates they can clean every couple of
weeks. Either is fine. What matters more are [a] a hiding place;
and [b] humidity. Provided they have these things, they really
aren't fussed. So a cave or hollow ornament or whatever where
they can hunker down periodically is useful, and as for humidity,
a plastic drip tray or even a regular hood should take care of
that. Within these restrictions, be creative!>
I have made her a larger land area by making a plateau out of the
gravel and siphoning out some of the water out. Seems to work ok
with the filter still circulating all the water through the
raised gravel area. She wants nothing to do with the
"land" area and dives right back into the water.
<Really? That's odd. Well, since I don't recognise the
crab to species level, let your observations be your guide. She
certainly should have land, but if she's nervous or otherwise
fussed about something, she will feel more secure under water.
Start off with a 50/50 mix of land and water, and see how you
Maybe that's just what she is used to. I hollowed out a spot
in the gravel so there is just a shallow pool. She is staying
there for the moment. As far as heat, get a heat rock?
<I'd recommend an under tank heating mat as being a lot
easier to use in this context.>
Of course that would require a real land area wouldn't
<Indeed. You may find that if the water area is big enough,
heating the water, and allowing the warmed air to circulate, will
do the trick. Really depends on how cold the air is in your part
of the world. If you're in
Southern California or somewhere with a subtropical climate,
merely warming the water would be adequate. Elsewhere, you really
want to heat up the whole enclosure.>
Again, I really appreciate your input.
Re: unknown crab 4/20/09
You are awesome.
We live in Texas, usually around 74, 75 in the house all year
round. Should be warm enough I'd think. She ate a nice piece
of cantaloupe while we were making breakfast. I feel much better
now that she has eaten something.
Here's a link to a site I found helpful as well.
<Have to confess that this isn't one of my favourite
sites; while it has a page on just about everything, it also
contains myriad errors and the writers seem to have a slap-dash
approach to healthcare and animal welfare.
They seem to offer feeder fish to just about everything, which to
me is a massive alarm bell that rings "bad
We will stick to the 20t for now as I am going to
"give" the crab to one of our 12 year old twins. You
are of course correct concerning manageability compared to the
55g. The other twin is getting a hand tame pair of
Fischer's lovebirds to "take care of". We all know
how that works don't we?
<Indeed... an issue I've commented on here before; by all
means share animals with children, but if any parent believes
their child will genuinely shoulder all the work (and expense)
they're likely to be in for a
Should be fair, we hope...
Again, thank you. We will let ya know how we progress. Have a
<I do hope so! And to you, too.>
Re: unknown crab, fdg., sys., beh.
I was mistaken when I said that the crab had eaten a nice piece
<Banana! Land crabs seem to love banana, the softer the
better! Also try small pieces of white fish, ideally lancefish,
which you can buy in pet shops. These have bones in them, and the
calcium there is excellent for the crabs. Unshelled prawns,
perhaps sliced along the middle to make things easier, are also a
good source of calcium. Crabs are scavengers, and generally eat
anything that's soft or meaty.>
My wife had removed it as it was getting a bit smelly. The crab
has not eaten anything since we got her and has seemingly become
<Review air temperature and humidity; these are essentially
like frogs in terms of care, and cold, dry air does them no good
at all. Turning the heater up in the water side of the tank can
create more warm, humid
conditions in the land side of the tank. Likewise, keeping the
lid more firmly secured will help, too.>
She has not moved much in the past 2 days. Maybe she's
getting ready to molt.
<You can actually check this: before they moult, crustaceans
absorb extra water. When picked up, you may notice they've
both bulked up and yet the shell is softer than normal, and may
even yield a bit to the touch. They feel less heavy for their
size that you'd expect (a tip you using when buying edible
crabs, by the way). While the following link refers to Land
Hermits, in terms of generalities, it would hold true for Land
So, prior to moulting, the crab will puff up, become softer, tend
to hide away from light, and generally become inactive. Moulting
starts with the exoskeleton unzipping, and the crab sort of backs
out of its shell,
I hope so. We would not feel like very good stewards if she
Already lost one pet this week :-( One of our Fischer's
lovebirds had a seizure and died in my hands.
<Oh, sorry to hear that.>
Of course, I have zero history on the crab. Have tried feeding
her a variety of foods to no avail. Any suggestions? Thanks.
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>
Bettas and brackish This question is threefold, but
background first. I have a two-year running planted tank with just
about the easiest to grow plants in them (hornwort and Cabomba weeds)
and a Betta (who is in heaven). Ten gallons, inexpensive waterfall-type
filtration turned all the way down to keep the water filtered but
generally undisturbed at the surface, temperature at 82-84F, full
spectrum lighting (as I pretty much used to use it as a plant-isolation
tank to get the snails out of them... used to have a swarm of apple
snails, which has since stabilized as the Betta tends to eat the egg
sacs and young snails... basically anything he could fit in his mouth).
It was my first foray into plants and gave me the knowledge I needed to
go into planting my goldfish tanks. <Outstanding> I am now
interested in getting some (generally) bottom-dwelling small crabs, and
according to the research I have done, while they can tolerate
freshwater (poorly), they prefer brackish. <Most of the species sold
in the trade, yes> I've done research into setting up a brackish
system and I feel ready for it. I've also been briefed in the
requirements of the types of crabs I'm considering (but will
eventually settle on a single pair of a single type, most likely the
small red-clawed crabs) and feel ready to meet them. <Okay>
Question one is: Can the Betta tolerate a brackish or
slightly-less-than-brackish salinity? <Yes... as can the
hornwort/Ceratophyllum... but the Cabomba may well do its falling apart
act> I'd like to keep him (I got him as a fry and know he is
around 19 months of age now) where he is, and possibly just slowly up
the salinity to desired levels to get him used to it, as well as
letting the microorganism population adapt to the change. <Good
technique> Question two: Would the Betta be socially compatible with
these scavengers? He generally will sleep on the plants and I've
almost never seen him sleep on the gravel (I work nights, and keep the
room dark on my nights off, so I have observed him during the
'night' part of his cycle). <The Betta should not harm the
crabs, but the reverse may well not be so... almost all crabs are
opportunistic omnivores... and if hungry, might attack, consume the
Betta> Question three: Answered on your brackish plants page, no,
the plants will stick around. Thank you, Dan <Be chatting, Bob
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 truly 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>
Crabby Conversion? - 08/07/2005
Can saltwater crabs adapt to fresh water? <Unfortunately, no. Thanks
for writing in! -Sabrina>
Halloween Land Crab 03/17/07 Hi,
thank you for taking the time to read this. I have what the pet store
called a Halloween Land Crab. <Gecarcinus sp., maybe G.
lateralis.> He is not set up in some amazing aquarium, he is just in
a plastic cage. I have a water dish for him that's 2 inches deep
that he climbs in and out of. The bottom of the cage is filled with
calcium sand and aquarium pebbles. <Ideally, he needs a sand
substrate deep enough and just damp enough to burrow into, and needs
enough saltwater and enough freshwater, each in separate containers,
deep enough to fully submerge himself - though the land area is by far
the most important.> He has been doing really well eating bits of
fruit such as apples, oranges, pineapple and also an occasional guppy.
<Needs more meaty foods, preferably things like human-consumption
shrimp (raw, frozen and then thawed) and fish; krill, meaty fish foods,
and also Nori (seaweed) would be other important foods.> But
recently three of his legs fell off on his right side! What is going
on? <Likely he is very deficient in something that he needs -
saltwater, perhaps, or iodine.... Feeding the foods mentioned above,
especially shrimp, krill, and Nori which are rich in iodine, will be
very important. Supplementing the food with a reptile calcium
supplement will be helpful, as well.> He was not in a fight with
another crab and I've never experienced him going through the
"shedding process"! Is he unhappy or sick? How can I tell
what's going on? <sounds like a state of disease, not a normal
molting situation at all.... I would urge you to improve this
critter's living space and food.> If this is below what you guys
do, then I'm sorry to waste your time, <A question is never a
waste of time.> I just need simple answers and can't seem to
find them anywhere. <Thank you very much for searching for your
answers, and for asking questions.> Nick <All the best to you,