FAQs on Freshwater
on FW Crabs by Species:
Vampire Crabs (Geosesarma
Bicolor), "Other" real and
purported Freshwater Crab species,
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, & FAQs
on: FW Crab Identification,
FW Crab Behavior,
FW Crab Compatibility,
FW Crab Selection,
FW Crab Systems,
Crab Feeding, FW Crab Disease,
FW Crab Reproduction,
Fresh to Brackish
FW Crustaceans 1,
FW Crustaceans 2,
Terrestrial Hermit Crabs, &
Marine: Hermit ID,
Parathelphusa pantherina, FW crabs and Juli's tog. in a 10 gal.
I recently acquired two very small Parathelphusa pantherina (shells just over
1.5cm across) and three juvenile Julidochromis marlieri (about 3cm long).
They're currently in a lightly planted 10 gallon grow-out tank with plenty of
rocks for the fish and some wood for the crabs to hide in. I know the tank will
be too small for them in the long-term and that it's not recommended to keep
crabs together with fish, but my crabs are so small and shy I can't imagine them
being able to do any damage to the Julies for a while yet.
<Mmm; yes; hard to imagine... but at night when the fish are settled down, near
the bottom, easily pinched>
And from what I understand they have similar pH and hardness requirements.
So I'm hoping to keep them in this tank for a few months until they all get a
little bigger. (Assuming I see no aggression of course.)
Which brings me to my three questions:
1.I haven't treated the tank with PraziPro yet. Is it truly safe for freshwater
<It should be; yes>
2. How will the Julies tolerate the extra iodine the crabs need?
<This too should not be problematic>
I do 50% water changes once to twice a week and add 1 drop of Kent Marine Iodide
to the change water every other time.
<No worries here>
3. At what size can I expect the Julies to start pairing up and become
<Another couple cm. With close observation you'll find this happening more in a
few months time>
Thanks for your help,
<Welcome! Bob Fenner>
Re: Parathelphusa pantherina 11/25/18
Thanks for such a quick response Bob! Will definitely keep a sharp eye out for
<Real good Rina. This is not a very "mean", territorial genus of Cichlids; and
less so w/ successive captive-produced generations. You'll see trouble coming.
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.
Panther Crab (Parathelphusa pantherina) color forms?
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
Thanks for answering my questions!
<Most welcome. Cheers, Neale.>
Re: Calcium Supplements for Panther Crabs?
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
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?
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
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.
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
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".>
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.>
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
<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
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
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
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
<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
<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