Red Claw Crab not Eating 12/29/19
Hello! Hardly anyone knows anything about red claw crabs, as I
cannot find any answers as to why my red claw crab has stopped
<Let's see if we can help.>
He is kept in brackish water conditions, has filtered water, and
water that is always about 74 degrees Fahrenheit.
<Right. Let's review first. By "brackish", how salty are we talking
about? The first thing you do when brackish water animals misbehave
is change the salinity. Many if not most come from places where the
salinity varies, so just making a change can have a positive effect.
But the bigger issue is that you need to be using a substantial
amount of salt, not the teaspoon per gallon amounts often mentioned.
I'd suggest one teaspoon per litre (i.e., a salt concentration of
about 6 gram/litre) to produce about one-sixth normal seawater
salinity. If that didn't do the trick, feel free to double that
amount, which would get you around one-third normal seawater
salinity. Either of these would be much closer to real world
situations for Perisesarma bidens. Next up, review air temperature.
23 C/74 F is very much towards the low end for a tropical animal,
and I'd crank the water heater up to 25 C/ 77 F. In cold conditions
tropical animals will slowly lose vigour, and loss of appetite is an
extremely common symptom of that. Death invariably follows soon
after, though it may take weeks to happen.>
He is able to climb to get air or be in water when he wants. I have
sand substrate. When I first got him, he would eat his food fine,
but now, he won’t eat at all. I noticed he wouldn’t eat, so I ended
up putting his food right in front of him, and he still won’t eat
<Loss of appetite in crabs is almost always a symptom of
environmental problems. Review as stated above.>
I don’t think he’s molting, because he’s been acting this way for
about 2 weeks and I was told molting should only take about a day.
<Correct, and moulting crabs tend to hide away. They do need a
source of iodine to moult successfully, for which purpose either
offer regular portions iodine-rich foods (Sushi Nori is ideal) or
else specific iodine-enriched crustacean foods sold for use in
Also, I don’t think it’s a calcium problem, as I give him special
vitamins that help provide him calcium every 3 weeks. I’m really
worried about him, and I have no idea why he is not eating.
<Hope this helps. Cheers, Neale.>
Re: Red Claw Crab not Eating
Thank you very much for this help! Right after I added more salt, he
molted the next day.
Does he absolutely need to eat his exoskeleton? If so, he is not
<No, he doesn't need to eat it, but most crabs do, simply to recycle
the calcium. If he doesn't, that's fine, but do add some suitable
replacement, like a small shell-on prawn that he can pick apart and
consume. Failing that, just dusting whatever he likes to eat (fish
meat, banana, etc.) with crushed cuttlebone or even fragments of
edible snail shells (escargot) will have the same usefulness. Some
crab foods are calcium-enriched and may be good enough on their own,
but personally, I'd make a point of offering
extra calcium immediately after moulting. Cheers, Neale.>
Re: Red Claw Crab not Eating 1/11/20
I’d like to thank you for helping me with my red claw crab.
Unfortunately, he has passed away even after adding a proper amount
of salt and turning up the temperature, as he just did not eat at
<I'm sorry to hear that.>
I don’t know the reason for his refusal to eat, but after taking
your advice, he seemed to have more energy and would actually
approach the food (but still didn’t eat it). Maybe he was sick?
<Indeed, or perhaps, he'd been away from salty water for too long.
These are tricky animals to keep well -- they need brackish water,
high humidity (cold or dry air quickly kills them), and food that
contains all the nutrients including iodine and calcium. So while
inexpensive in themselves, and not demanding in terms of space, they
I don’t know, but I’m glad I found your website and got some help.
You are very knowledgeable about these creatures, and people who are
having trouble with their pet crabs are fortunate enough to be able
to contact you for help. Again, thank you very much.
<You are most welcome, and thanks for these kind words. Good luck
with your next pet! Cheers, Neale.>
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