Quick answer
Caridina japonica is the older scientific name for the shrimp now classified as Caridina multidentata, and known to most aquarists as the Amano shrimp. It is a freshwater shrimp native to Japan and Taiwan, reaching around 2 inches (5 cm), living roughly 2 to 3 years, and kept mainly for algae grazing in planted tanks. It needs a mature tank of at least 10 gallons, stable water around 18 to 27°C (65 to 80°F), and absolutely no copper. It will not breed in a normal freshwater aquarium, because the larvae require brackish water to survive.
If you have been reading about this shrimp, you have probably run into three or four different names for it and wondered whether they are the same animal.
They are. Caridina japonica, Caridina multidentata, Amano shrimp, Yamato shrimp, Japanese marsh shrimp, and algae shrimp all describe one species. This guide covers the naming, identification, care, feeding, breeding, and the problems people actually run into.
I have kept them myself, though not currently.
Caridina japonica at a glance
| Scientific name | Caridina multidentata |
| Former name | Caridina japonica |
| Common names | Amano shrimp, Yamato shrimp |
| Size | 2 inches (5 cm) |
| Lifespan | 2 to 3 years |
| Tank size | 10 gallons and up |
| Temperature | 18 to 27°C (65 to 80°F) |
| pH | 6.5 to 7.5 |
| Diet | Biofilm, soft green algae, leftover food |
| Breeds in freshwater | No, larvae need brackish water |
| Difficulty | Easy, in a mature tank |
Caridina japonica or Caridina multidentata?
Both are correct, but one is current.
Caridina japonica was the accepted scientific name for years. It is still what a lot of shops, forums, older care sheets, and long-established shrimp sites use.
Caridina multidentata is the current accepted name after the species was reclassified.
Nothing about the animal or its care changed. If you bought shrimp labelled Caridina japonica, you have Amano shrimp, and every multidentata care guide applies to them. The practical takeaway is not to dismiss older japonica pages as outdated, or newer multidentata pages as being about something else. They are the same shrimp.
Where the common name comes from. Takashi Amano, the Japanese aquascaper, popularised them in the 1980s after noticing their appetite for algae. The hobby has called them Amano shrimp ever since.
Identifying Caridina japonica
Appearance. A translucent grey to light brown body, with a row of dots and dashes running along each side and a pale stripe down the back. The body is largely see through, which is why they can look almost ghostly against dark substrate.
Size. Around 2 inches (5 cm) as adults, roughly double the size of a cherry shrimp. Females tend to be slightly larger.
Lifespan. Around 2 to 3 years in a stable tank, sometimes longer.
Male vs female. The side markings are the easiest tell. Males have evenly spaced dots along the flank. Females have longer dashes rather than dots, and are noticeably larger and fuller bodied. In a mixed group the difference is obvious once you know what to look for.
Caridina japonica care and tank setup
They are genuinely hardy, which is why they get recommended so often. Hardy does not mean requirement free.
Tank size. 10 gallons minimum. They are active and larger than dwarf shrimp, and they need surface area to graze.
A mature tank. This is the requirement most often skipped. Amano shrimp feed on biofilm and algae, and a tank running for a week has neither. Adding them to a brand new setup is the most common reason they struggle or die early. Wait until surfaces have developed a film.
Water parameters. Temperature around 18 to 27°C (65 to 80°F), pH roughly 6.5 to 7.5. They tolerate a reasonable range, and stability matters far more than hitting an exact number.
Substrate. Not fussy. Sand or gravel both work, since they graze surfaces rather than dig.
Plants and hardscape. Cover matters. Moss, wood and plants give grazing surfaces and somewhere to hide, which is important right after moulting when they are soft and vulnerable.
Filtration. Use a sponge filter, or a guard on the intake. Shrimp get pulled into unguarded intakes.
Copper is the hard rule. Copper is toxic to invertebrates. Check every medication, plant treatment and fertiliser for copper before it goes anywhere near the tank. This is the fastest way to lose a whole group.
What does Caridina japonica eat?
They are constant grazers and opportunistic scavengers.
Biofilm. The microbial layer that develops on surfaces in a mature tank. This is a staple, and it is why a sterile new tank does not support them. It is the same white biofilm that appears on new driftwood, which they will graze happily.
Algae. The reason most people buy them. They are effective on soft green algae. Reports on hair algae vary, and some experienced keepers argue their appetite is more limited than the hobby generally claims.
Leftover food and decaying plant matter. They clean up what fish miss.
Supplementary food. In a clean, algae-poor tank they need feeding. Blanched courgette or spinach, and prepared shrimp foods, both work. Feed sparingly.
An honest note on algae control. Amano shrimp are not a cure for an algae problem. Their appetite is finite, and a shrimp group cannot out-eat an ongoing imbalance in light, nutrients and carbon. Buying them to fix an outbreak usually disappoints. Treat the cause, and treat their grazing as maintenance rather than a solution.
On black beard algae specifically. They will sometimes pick at BBA, particularly if little else is available, but they are not a reliable answer to it. I went through what actually works on BBA, and which animals genuinely eat it, in my black beard algae video.
One caution. Hungry Amano shrimp can pick at soft new plant growth. It is uncommon in a well fed tank, but “they never touch plants” overstates it.
Tank mates
Generally safe: small peaceful community fish, other shrimp species, snails, and most small tetras and rasboras.
Risky: anything with a mouth big enough for a 2 inch shrimp. Larger cichlids, big gouramis and most predatory fish will treat them as food.
Worth knowing: they are assertive feeders. Fast, larger than dwarf shrimp, and they will muscle in at feeding time. In a tank with shyer shrimp, make sure everyone actually eats.
Breeding Caridina japonica
This is the part that makes the species interesting, and the part most guides handle badly.
In a normal freshwater tank, they will not breed successfully. Females carry eggs readily, and a berried female is common in a healthy tank. The problem comes after hatching. The larvae are not miniature shrimp, they are planktonic, and they need brackish or salt water to develop. In freshwater they die within days.
What deliberate breeding involves:
- A berried female carries eggs for several weeks
- Larvae hatch and must be moved to brackish or salt water promptly
- They feed on phytoplankton or fine algae based foods while developing
- After several weeks they metamorphose into recognisable juvenile shrimp
- The juveniles must then be acclimated back to freshwater gradually
Be careful with the specifics you read. Sources genuinely disagree, particularly on the salinity required and the exact timings. This is one of the least settled areas in shrimp keeping, so treat any single confident number with caution and read more than one account before attempting it.
The practical takeaway. If you want a self sustaining colony, Neocaridina (cherry shrimp) breed freely in freshwater and are far easier. Amano shrimp are ideal precisely because they will not overrun your tank.
Common problems
Turning white or opaque. The most common panic. A milky white, motionless shrimp is usually dying or dead. But a clear, hollow, shrimp shaped shell is a moult, which is completely normal. Check whether it is hollow before assuming the worst.
Moulting problems. Shrimp shed their shell as they grow. A failed moult, where the shrimp gets stuck partway, is often linked to unstable parameters, particularly sudden mineral changes during a water change. Slow, consistent water changes help more than any additive.
Hiding constantly. Normal for a while after being added, and normal straight after a moult. Persistent hiding in an established tank suggests stress, water quality problems, or a tank mate bothering them.
Frantic swimming around the tank. Sometimes a male chasing a newly moulted female, which is normal. But if the whole group is doing it, test your water before assuming courtship.
Sudden deaths after a water change. Usually a parameter swing or something in the tap water. Shrimp are far more sensitive to abrupt changes than fish are.
Signs of a healthy Caridina japonica
Constant grazing. A healthy Amano shrimp is almost always busy, picking over plants, wood and glass.
A clear, translucent body with the dot and dash markings visible along the sides.
Regular successful moults. Finding empty hollow shells is a good sign, not a bad one.
A strong appetite. They should come out when food goes in and be assertive about it.
Alert, responsive movement rather than drifting.
Berried females, if mature. A female carrying eggs means good conditions, even though the eggs will not produce surviving shrimp in freshwater.
Caridina japonica vs cherry shrimp
- Size: Amano shrimp are roughly twice the size
- Colour: Amanos are translucent grey, cherries are bright red
- Algae grazing: Amanos are considerably more effective
- Breeding: cherries breed freely in freshwater, Amanos effectively do not
- Best for: Amanos for grazing in a planted tank, cherries for a self sustaining colourful colony
Plenty of planted tank keepers run both.
Mistakes to avoid
Adding them to a brand new tank. No biofilm, no algae, nothing to eat.
Any copper containing treatment. Check every label.
Expecting them to solve an algae outbreak. Their appetite is limited. Fix the cause.
Assuming every white shrimp is dead. Check for a hollow moult first.
Buying just one or two. They are more relaxed and more active in a group.
Unguarded filter intakes. An easy and avoidable loss.
FAQ
Is Caridina japonica the same as Caridina multidentata? Yes. Caridina japonica is the older scientific name and Caridina multidentata is the current one. Both refer to the Amano shrimp, and care requirements are identical.
What is Caridina japonica? A freshwater shrimp native to Japan and Taiwan, kept in planted aquariums mainly for algae grazing. It is commonly sold as the Amano shrimp or Yamato shrimp.
How big does Caridina japonica get? Around 2 inches (5 cm) as an adult, roughly twice the size of a cherry shrimp.
How long does Caridina japonica live? Around 2 to 3 years in a stable, mature tank, sometimes longer.
What water parameters does Caridina japonica need? Roughly 18 to 27°C (65 to 80°F) and a pH near 6.5 to 7.5. Stability matters more than exact figures, and copper must be avoided entirely.
Can Caridina japonica breed in freshwater? Not successfully. Females carry eggs, but the larvae need brackish or salt water to develop and do not survive in a freshwater aquarium.
How do you tell male from female Caridina japonica? Look at the flank markings. Males have evenly spaced dots, females have longer dashes and are larger and fuller bodied.
Does Caridina japonica eat algae? Yes, mainly soft green algae, and it grazes biofilm constantly. It is not a cure for an algae outbreak, since its appetite is limited.
Why is my Caridina japonica turning white? A milky white, motionless shrimp is usually dying. A clear, hollow shell is a normal moult. Check whether it is empty first.
How many Caridina japonica per gallon? A common guideline is roughly one shrimp per 2 gallons, adjusted for how much algae and biofilm your tank actually supports.
Final word
Caridina japonica, Caridina multidentata, Amano shrimp. One animal, three names, and none of them changes how you keep it.
Give them a mature tank with something to graze, keep parameters stable rather than perfect, guard the filter intake, and keep copper well away. Most problems with this shrimp trace back to one of those four things.
And do not buy them expecting an algae cure. Buy them as a useful, hardy, long lived grazer that will quietly earn its place, and you will not be disappointed.
