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Everything About Caridina japonica

		Japanese swamp shrimp, Amano shrimp, and the Yamato numa-ebi, all refer to the same great algae eater, Caridina japonica. Without a doubt, Caridina japonica is one of the best algae eaters for a freshwater aquarium. Unfortunately, the distribution of these shrimp is limited to only a handful of Asian countries. Lately many of these great shrimp are showing up in North America.

  Since very little is known about these shrimp outside of Japan, I have decided to write this. I have lived in Japan for over five years, and I have used Caridina japonica for nearly that long. I have talked with a few aquarium retailers about these shrimp, and purchased some magazines with Caridina japonica articles. My Japanese wife Hiromi, has helped me with the translation, when necessary.

History:
  As the name implies, The Japanese swamp shrimp come from many different swamps here in Japan. My friend at the local aquarium store, says that his wholesaler collects these shrimp from the wild on the southern island of Japan (Kyushu). The photographer, artist, author, and aquarist, Takashi Amano was the first one in the world to widely use this type of shrimp. Amano started using these shrimp in the early 80's. Now, no tank he creates would be complete without these little guys.

Description:
  Caridina japonica can reach a length of almost 2 inches (5cm) from nose to tail. Body color consists mostly of a light brown opaque color. On the back carapace, there is a tan stripe that runs from the head down to its tail. On the shrimp's side flanks, are a series of broken lateral lines that are a reddish-brown in color. The tail also contain two or more black and white dots.

Diet:
  Caridina japonica has been known to eat almost every kind of algae known to the aquarist. But Yamato numa-ebi are finicky when it comes to how much, and of what type of algae to eat. One algae that Yamato numa-ebi do not like, is the dreaded black beard algae. Nevertheless, when they are hungry they will gnaw away at some of it. These shrimp are most active at night, but seem to do a decent job during the day, also. Even if there is an abundance of algae in the tank, I have observed these shrimp taking fish food from the surface of the water. In rare cases, Caridina japonica has even been known to eat plants. I have witnessed them eat my nice lawn of Riccia, due to the fact that the shrimp I had bought were bagged for two days with nothing to eat. Along with eating some living plants and algae, Yamato numa-ebi will also eat detritus in the form of dead plant leaves and leftover food.

Care:
  Japanese swamp shrimp are very tolerant when it comes to water type. Since they come from swamps, they can also tolerate different salinity. Another parameter that is tolerated by these shrimp is pH. Amano, and I, use these shrimp, and our pH is about 6.5 with the use of Aqua Soil. Since Caridina japonica originate from a swampy/marsh region with brackish condition, I would guess that a pH well above 7 is also fine. These shrimp have been known to live up to three years in captivity. I personally have had one for nearly two years. Two things to point out, the Yamato numa-ebi are very sensitive to ammonia/ammonium, and heavy metals. Heavy metals will interfere with the shrimp's molting process causing them to die. Ammonia and ammonium are just simply poisonous to all living things.

  Almost all Cichlids will take a liking to these shrimp, meaning they will eat them. These is only one kind of Cichlid that I know that does not harass these shrimp and that is the ramirezi. Most other community fish should coexist with them.

  Transporting any kind of ship can be hard since they will suffer from ectodermic shock (I think that what it is called) from the plastic bag if they do not have anything to cling on to. My LFS always provides a plastic mesh for them to hold on to until I get them home. If something is not provided during transportation in a plastic bag they would surely die.

  Acclimating any shrimp must be done slowly as they are sensitive to change. I have spent up to an hour pouring aquarium water in the bag

  Other than these simple rules, Caridina japonica require no other special needs.

Breeding:
  Caridina japonica on the other hand, is certainly a challenge. Few people have breed them, and even fewer have been able to raise the larva for more than a week. The conditions and factors regarding breeding is still foggy. It is speculated that Caridina japonica might spawn, or whatever crustaceans do, in brackish/saltwater, and then return to freshwater. This seems to match what one German aquarist accomplished. With a rough translation with Alta Vista's Babblefish it appears that a brackish condition does encourage breeding as does as temperature of 25~26.5 degrees Celsius. The mating season seems to be in late Spring or early Summer. I base this on the fact that I have bought Caridina japonica during these times with big females holding eggs. One female held this clutch of eggs for about a week after I bought her. After that time I did not see the eggs again. I looked in the tank for larvae, but found none. This is the same thing that happened to the other females that were holding eggs.

  A diet of green water for the first few weeks and an abundance of algae might help to raise the young, but once again this is pure speculation on my part.

  What I do know is that the young must be removed from the display tank if you are serious in raising them. A sponge filter would be ideal, since a power filter would eat them as quick a fish would. I have also bet that the parents will cannibalize their young too.

  There is a shrimp that looks similar to Caridina japonica, and it has been known to breed in the aquarium. This shrimp is known as the southern swamp shrimp (Minami numa-ebi) in Japan, or scientifically as Neocaridina denticulata. Neocaridina denticulata is smaller in size and less opaque than Caridina japonica. I have seen Neocaridina denticulata mixed in with Caridina japonica before at aquarium stores. Unfortunately, I do not know the details regarding the breeding of Neocaridina denticulata. It is possible that the conditions would be the same as C. japonica

Closing:
  In the future I hope to see more of these shrimp in America. It would be a shame to not be able to use them in America too. Not only are they a great 'clean up crew' but they are cute and full of energy. If you know more about these shrimp, or have been able to breed them please let me know.

  I have seen many stores here in Southern California selling 'Algae Shrimp', but they are not Caridina japonica. Arizona Aquatic Gardens is currently selling these shrimp. The price is a little steep with shipping. One day we might all be able to get them locally.

Ryan Stover
ryan at suiso.com

More Info on breeding and raising these shrimp:
Joe's Aquatic Lounge Shrimp FAQ's
Heather Canderlaria Breeding Report Part 1  Part 2