How to Take Care of Japanese Freshwater Crabs (Sawagani)

Freshwater crab - Potamonautidae, sawagani

Freshwater crab; Photo by brian.gratwicke

“Sawagani,” which translates to Japanese Freshwater Crab, is the only freshwater crab found in Japan.  While it is more popular to eat sawagani once they’ve been caught, it can also be quite an interesting experience to keep these freshwater crabs as pets.

Materials for Japanese Freshwater (Sawagani) Crab Care

Container

As a container, some people use a medium-to-large flower-pot from a garden center for their sawagani crab, which is fine.  Others prefer a plastic case, since you can see the crabs from the side.  Keep in mind that a case/container that is too shallow will be easy for the sawagani crabs to escape.

Water

The water in the container should be freshwater, preferably without chlorine. Leave tap water sitting out for a day before introducing the sawagani crabs into it. This will ensure that the water becomes de-chlorinated.

Food

Crabs eat a wide variety of items. Suitable foods include boiled rice, cabbage, small crunchy dried sardines, young sardines, tubiflex worms, sliced dried bonito, and bread. Special food isn’t required, though you could certainly buy special crab or crayfish targeted food from a pet store.

Small Food Dish

You should prepare a dish in which to put the sawagani crabs’ food. This keeps the food from being scattered around and making the water dirty.

Shore Materials

You should use materials to create a “shore” inside the container. You can use pebbles, dirt, sand, or rocks.

Hiding Places

Sawagani crabs need hiding places. You can use larger rocks, roof tiles, broken pots, branches, or anything else under which they can hide.

Water Plants

Water plants aren’t absolutely necessary, but they can help keep the air fresh and can be eaten by the crab in a pinch.

Water Purifier and/or Oxygenator

A water purifier and oxygenator are optional, but some sawagani crab owners chose to use these. Make sure the crabs don’t escape by climbing up any of this equipment.  They are quite good at climbing.

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Sawagani Crab Care Instructions

Finding Sawagani Crab

Acquire your new friend.  Sawagani crabs often live in freshwater streams and creeks in mountains in Japan. Also, some pet shops and grocery stores sell them.

Don’t put too many crabs in the container.  Crowded conditions will make sawagani crabs stressed.  One male and one female is recommended.  Also, if you place two crabs in the same container, please be sure that they are about the same size.

Sawagani Crab Container

Prepare the container. Put pebbles, dirt, and/or sand in the bottom of the container at a slope. This is to create a “shore” for the crabs to climb up on. You can also add larger rocks or any kind of decorative object for the crabs to climb on. Add at least 2 to 3 centimeters (about 1 inch) of freshwater. 

Sawagani crabs are quite sensitive to heat, so a little more than that would be preferable. This prevents the water from getting too hot or evaporating. Also, if you use tap water rather than bottled, let the tap water sit out for a day before introducing the sawagani crabs into it. This will ensure the water is de-chlorinated. 

Also, place branches, larger rocks, and/or broken pottery into the container so that the crabs have a hiding place. If you choose, you can also put in water plants, a water purifier, and/or an oxygenator.

Put the container in a cool area, out of the sun. Sawagani crabs are very sensitive to heat and will die if put directly in the sun or in an area that’s too hot. Make sure that the area also has good, cool ventilation. 

In the summer especially, it is best to err on the side of caution and keep them indoors. If the temperature reaches over about 28 Celsius (about 82 Fahrenheit), the crabs will almost certainly die.

Cleaning the Container

Change the water if it starts getting dirty. This should be about once or twice a week. It is okay to change the water all at once, rather than gradually, like with other water-dwelling-pets. If the crabs start blowing bubbles, this means the water is dirty and the oxygen level is low, so please change the water.

If you choose to use a water purifier or oxygenating equipment, be cautious. Crabs are able to climb quite well and it isn’t unheard of them to escape by climbing up a water purifier.

Feeding Sawagani Crabs

Crabs are omnivores, which means they eat a wide variety of things and will live a long, healthy life if you give them that variety. 

Feeding once every other day is sufficient. Sawagani crabs eat much less than expected. Don’t feed them too much and be sure to remove uneaten food so it doesn’t rot. 

Good foods include:  smooshed rice, cabbage, small crunchy dried sardines, young sardines, tubiflex worms, sliced dried bonito, and bread. Sawagani crabs don’t really need special food, but you can also use pet store crab and crayfish food. 

Place the food in a small food bowl so that it will be less likely to be scattered around and make the water dirty.

Sawagani Crab Molting

When the sawagani crabs are molting, their bodies become soft, so please don’t touch them during this time.  Also, the crabs sometimes may turn to cannibalism when molting, so don’t keep too many crabs in one container.

Sawagani Crab Hibernation

In winter, sawagani crabs hibernate. Place them in an area where the water and dirt won’t freeze and also place a little more dirt in the container. The crabs will dig a hole in the dirt/sand/etc. and hibernate there until spring. If they can’t dig a deep enough hole, they will hide under a large rock or other object to hibernate.

Sawagani Crab Tips and Facts

Male and Female Crabs

You can differentiate between males and females by their stomach and claw shape.  If the right claw is bigger than the left claw, the crab is a male.  On females, both claws are the same size.  On males, the stomach has a bit of a pointed, triangular shape, whereas on females, the stomach is more rounded.

Breeding Season

Japanese freshwater crab breeding season is from about April to July.  The females lay eggs and, after about a month, the eggs will hatch. 

If you go swimming or boating in June in Japan, you may have the chance to catch baby crabs.  Taking care of young crabs is the same as taking care of the parents.

If you do happen to breed crabs, be sure to keep the young separate from the parents.

Eating Sawagani Crabs

Please note that while many foods in Japan are served raw, freshwater crabs are an exception and should not be eaten raw, as they often have parasites. Although I don’t know why you’d want to consider eating your new friend 😉

Sawagani Crab Lifespan

I couldn’t find much information on the crabs’ lifespans, but it seems one pet-owner made it through at least one year with his.

Disclosure

Please keep in mind that I am not an expert on crab care. All of the information provided here was compiled and translated from the sources listed below. Thank you for your understanding.

Sources

Sawagani no kaikata

I’ve also compiled care instructions for yago (dragonfly young), so please click here to see the post.

Thinking of getting a kabuto mushi (rhinoceros beetle)? Check out these care instructions!

How about a kuwagata mushi (stag beetle)? Then take a look at this article.

4 thoughts on “How to Take Care of Japanese Freshwater Crabs (Sawagani)

  1. Peter says:

    Thanks! Daughter just caught one in the mountains and wanted to keep it. Super useful.

    Reply
  2. hana says:

    Where can these be caught? Honshu only? Were they ever introduced to rivers in Hokkaido?

    Reply

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