Amano shrimps in the aquarium | Shrimp | Blog

Amano shrimps in the aquarium | Shrimp | Blog

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What makes an amano shrimp?

The Amano shrimp or Yamato shrimp (scientific name Caridina multidentata) is a rather large dwarf shrimp, probably the largest in aquaristics. Its size is only surpassed by fan shrimp and some large-armed shrimp.Sexually mature Amano females reach 5-6 cm body length, the males remain much smaller at about 4-4.5 cm.

Most Amano shrimps show the wild colouration: they are more or transparent to greenish or brownish, some Amanos can also develop a grey to bluish cover colour. A fine, light-coloured, brown-lined dorsal stripe runs across the back. This makes amano shrimp perfectly camouflaged in foliage and detritus at the bottom of the water. On the side of the belly, amano shrimp show a reddish brown to dark brown dot pattern or a short line pattern.

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The life expectancy of the very adaptable amano shrimp in the aquarium is between 7 and 10 years – there are also reports of animals that became even older. A very respectable age for dwarf shrimp!

Colour breeding of amano shrimps – white Caridina multidentata

Until a while ago it was said that there was no colour breeding in Amano shrimp, but now this has changed! White Caridina multidentata, the Caridina multidentata “Snow”, have been available for several months. Our Snow amano shrimp were bred in Taiwan. The breeder assumes that it is a mutation that remains permanently white.

“White” amano shrimp have been shown before, but these breeding forms had to be kept rather dark and needed a special food – sooner or later, however, these animals eventually became wild coloured. This is different with the Amano shrimp “Snow” – these animals have shown themselves to be permanently white in long-term tests at our aquarium facility in Mannheim, so it can be assumed that they should tend not to change colour.

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Sex differentiation in Amano shrimps

Differentiating the sexes of Amani shrimps is actually very easy: On the one hand, the females are clearly larger and appear much more bulbous than the males, on the other hand, thanks to the transparent basic colouration, the greenish grey egg spot in the neck of sexually mature females can be seen very clearly – or the similarly coloured eggs in the abdominal pockets under the abdomen when the Amani females are carrying.

The pattern, however, is really simple: wild-coloured amano females have a pattern of short horizontal lines on the abdominal sides, while wild-coloured males show a dot pattern. This pattern, which differs according to sex, is also called sexual dimorphism. However, this criterion does not apply to the white snow amano shrimp.

Also, this deviating pattern only appears in somewhat older amano shrimp, in juveniles this characteristic is not yet fully developed, just like the other characteristics for sex recognition.

In the trade you usually get young animals where you cannot yet say for sure which is male and which is female. Because the sex distribution in a litter of Caridina multidentata is more or less 50:50, it is best to start with a larger group of young Amano shrimp if you want to breed specifically. The chances are then good that there will be both males and females in the group.

Where do amano shrimp originally come from?

The first amano shrimp on the market were imported from Japan. At that time, amano shrimp were consequently also known under the scientific name Caridina japonica (Japanese shrimp). In the meantime, it is known that there are also occurrences of these beautiful large dwarf shrimps in Taiwan and Korea – and even on Madagascar! The Madagascan Amana shrimp could belong to a subspecies, but it is also possible that it is a completely separate species – genetic studies are still pending.

The Amano shrimp got its Japanese name Yamato numa-ebi (or Yamato shrimp) because it was first found in Japan in the Yamato province.

How do amano shrimps live in nature?

In their native waters, amano shrimp are found exclusively in the freshwater of rivers that flow into the sea. The shrimp apparently migrate upstream against the current their entire lives. Therefore, the largest specimens of Caridina multidentata are found in the upper reaches of rivers.

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Amano shrimps also climb over larger obstacles during this migration against the current – they may even crawl a short distance in the air – as long as the gills are moist, these shrimps also survive above water. With powerful flicks of their tails, migrating amano shrimp catapult themselves over stones, small rapids and other obstacles.

If you keep amano shrimp in an aquarium, they will not be able to completely abandon this natural behaviour – again, following their migratory instinct, they like to go against the water current and may even jump out of the aquarium. It takes a while for this behaviour to subside, especially in wild-caught fish. Therefore, you should make sure that the aquarium is well covered for your new Amano shrimp and that they do not find any gaps through which they can jump. Especially the cable shafts in the back of the cover should be plugged with some filter floss or filter sponge.

What do amano shrimp eat?

In the wild, amano shrimps feed on algae deposits and biofilms, on fallen leaves in the stream and on plant remains, on dead animals, on worms and insect larvae and so on. The small saprobionts or destructors thus act more or less as a clean-up squad and health police in the streams of their biotopes.

Amano shrimps also eat remains in the aquarium: leftover fish food, dead snails and shrimps, algae deposits (even soft filamentous algae!), biofilms, plant remains, dead fish, … everything that is left over in the aquarium. As a rule, Amano shrimps do not eat healthy plants.

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In addition, especially female amano shrimps sometimes cover their increased protein requirements with a living snail during egg production, and very rarely it has been observed that they even go for healthy fish. However, this should still be an exceptional case! Most amano shrimps are very peaceful aquarium inhabitants.

The increased protein requirements of adult females can be met by feeding them appropriately – frozen food, protein food for shrimps and also FD food are readily accepted and can prevent the females from nibbling on snails, other shrimps and other tank mates.

Moulting in Caridina multidentata – what do I have to consider?

Shrimps do not have bones, but an exoskeleton – their carapace made of tough chitin and lime, which becomes slightly elastic due to the chitin and very stable and firm due to the lime. Less lime is deposited on the joint membranes so that the shrimp can move. This is also the case with the Amano shrimp.

Because shrimps grow throughout their lives, they have to shed this firm shell from time to time and replace it with a new, larger one; they are said to shed their skin.

Underneath the old shell lies the skin, which is still quite soft at first. In order to adjust the size of its new shell, the Amano shrimp pumps itself up with water directly after moulting, so that the new, still soft skin fits tightly. Over time, the water pumped into the shrimp’s body is replaced by the body’s own tissue – allowing the animal to grow. After moulting, the Amano shrimp is about 10% larger than before moulting.

Before moulting, the shrimp extracts lime from its old skin, which it stores temporarily in its body. After moulting, the lime is gradually stored in the new skin, making it stable again.

Female amano shrimp are only ready to mate after moulting. Once the carapace is solid again, they cannot carry their eggs under their swimming legs.

The time directly after moulting is the most dangerous for an amano shrimp – if there is a lack of protein, other Caridina multidentata like to help themselves to the soft conspecifics weakened by the moult and eat them. So always make sure that there is a sufficient protein supply as well as sufficient hiding places where the freshly skinned shrimp can take cover.

The reproduction of Caridina multidentata

Immediately after moulting, mating-ready female amano shrimps emit so-called pheromones into the water, well-smelling attractants that can be perceived by the males of their own species and trigger them to swim to mate. The male amano shrimp buzz around the aquarium looking for the female that is ready to mate.

During the so-called mounting, one or more males sit on the back of the female shrimp and slide down her side so that they can deposit their sperm packets (also called spermatophores) between their front legs.

After a successful mating, the female presses her eggs from the ovary (egg sac) in the neck through the oviduct to the oviduct opening between the last pair of walking legs. As they slide past, they are fertilised by the attached spermatophores.

The lady amano shrimp then attaches the eggs to her swimming legs with a sticky thread, the filament. As they slip past the spermatophores, the eggs are directly fertilised.

Female amano shrimp carry over 1000 tiny eggs per litter. They remain attached under the abdomen until hatching, where the female sorts, cleans and fans them with oxygen-rich water until the larvae hatch. The females recognise unfertilised eggs, dirt, rotting or mouldy spawn thanks to the olfactory cells on their swimming legs and selectively sort them out.

The eggs are greenish grey at the beginning and become lighter and lighter during the gestation period. If you have a good magnifying glass and look very closely, you can see tiny black pairs of eyes in the eggs towards the end, shortly before the larvae hatch.

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Amano shrimp larvae usually hatch at night. The larvae are positively phototactic and always swim specifically towards the light.

Amano females carry their eggs for four to six weeks. In warmer water, the gestation period is less long than in cool aquaria.

The tiny eggs do not hatch into ready-made juvenile shrimps, as would be the case with Neocaridina or with bee shrimps, tiger shrimps and other dwarf shrimps, but into very small zoea, larvae only about 1 mm long. The larvae float upside down in the water and are very difficult to spot.

In freshwater, Amana larvae survive for about four to five days. In nature, they drift with the current to the river mouth or even all the way to the sea. In brackish water with seawater, the zoea larvae of the Amana shrimp develop into the finished shrimp.

In the aquarium, of course, the Amana larvae cannot drift into the sea – here the shrimp farmer must transfer the small larvae from fresh water to salt water in good time.

Amano shrimps bred in Germany (DNZ) are becoming increasingly popular in aquaristics. Amanos bred here are much more resource-efficient than animals that have to travel the long way from Asia as imported animals or wild-caught. You will also find DNZ Amano shrimps in our shop!

If you would like to try breeding amano shrimps yourself, we explain how to do it in our blog Breeding amano shrimps in the aquarium.

Can amano shrimps also reproduce in freshwater?

Every now and then we hear that Amani shrimp larvae also grow up in freshwater aquariums – however, these are usually only isolated accidental offspring that are not sufficient to maintain the population. In most cases, there is confusion with wild-coloured Neocaridina or Sulawesi Island shrimps. In the few cases where Amana larvae actually grow large, they swam in very hard water with a shifted calcium-magnesium ratio and quite a high proportion of magnesium in the aquarium water.

What explains the large distribution area of Caridina multidentata?

The larvae of Caridina multidentata that grow up in the sea do not necessarily return as a finished shrimp to the exact river from which they were drifted into the sea. Like most shrimps with marine larval stages, Amano shrimps have a very large range in nature. Amano larvae from the sea can thus, with a bit of luck, migrate to new rivers as juvenile shrimp and colonise new habitats, and this is noticeable in their large range across several islands and coasts.

The dear relatives

The Amano shrimp belongs to the species group around Caridina weberi. Here, related species of dwarf shrimp are grouped together, most of which belong to the so-called primitive reproduction type – this means that, like amano shrimp, they do not release ready-made juveniles into the water, but tiny zoea larvae that live suspended in the water as part of the zooplankton and need salty water to develop. The adult shrimps of the weberi group, on the other hand, mostly live in freshwater.

All for science – what does research say about the amano shrimp?

The amano shrimp Caridina multidentata belongs taxonomically to the decapod order (Decapoda), the suborder of shrimps (Caridea) and the family Atyidae. The species was first scientifically described by the US zoologist and naturalist William Stimpson in 1860. In his first description, Stimpson gave the shrimp its species name Caridina multidentata, which means many-toothed Caridina shrimp and alludes to the rostrum of the Amano shrimp, which is covered with many small teeth.

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In 1892, the Amana shrimp was scientifically described for the first time by the Dutch biologist Johannes Govertus de Man, who was not familiar with Stimpson’s work. This time, the animals were given the name Caridina japonica – and this is how they were known in aquaristics for a long time. It was not until 2006 that the researchers Yixiong Cai, Peter K. L. Ng, Shigemitsu Shokita and Kiyoshi Satake noticed during their revision of various species that the older first description by Stimpson already existed for the Amano shrimp. Because in taxonomy the oldest species name is also the valid name, Caridina multidentata was elevated to the valid name by Cai, Ng, Shokita and Satake and Caridina japonica was declared a synonym.

Caridina multidentata (or Caridina japonica, as it was then called) was initially known in aquaristics as Japanese shrimp or Yamato shrimp – but then the ingenious aquarium designer, aquascaper, nature photographer and father of the natural aquarium Takashi Amano discovered how useful the ever-hungry little shrimp are as algae eaters in planted aquariums. He put the efficient algae shrimps in each of his natural aquariums to keep them algae-free and photogenic. Through Amano, the shrimps became world-famous and quickly acquired their trivial name Amano shrimp.

Even in aquariums that are not set up by master aquascapers, amano shrimp do a good job as efficient algae police. Especially the young females are excellent algae eaters, even taking care of the rather hard to eat filamentous algae and furry algae.

If you observe algae-eating Amano shrimp, you will see that they bite off small pieces of the algae with their powerful mouthparts.

How do I set up the perfect aquarium for amano shrimp?

The aquarium for the large Amano shrimp, which are very lively especially during mating swims, needs an edge length of at least 60 cm, even 80 cm is better, so that they can show their full range of behaviour – larger is of course no problem for the great dwarf shrimp! Because Amano shrimp jump well and like to go against the current, the aquarium must be covered to prevent escape, especially at the beginning. Current can, but does not have to be.

There are no limits to your imagination when it comes to setting up the aquarium. Amano shrimp like a good structure with roots and stones that offer them hiding places. They love to graze on biofilms growing on them.

Free swimming space is gladly accepted, especially during mating swims. The substrate does not play a major role in the living conditions of the Amano shrimp in the aquarium – gravel, sand, soil – everything is possible. Caridina multidentata does not eat healthy aquarium plants, but it will eat dying leaves. They love thread algae and other green algae, as well as brown autumn leaves.

The right water values for Amano shrimps

Amano shrimps are not very fussy about the water values in the aquarium and do very well in soft to hard freshwater. They are also not restricted to a narrow range of water temperatures, but can tolerate a temperature range between 18 and 30 degrees. You do not necessarily need a heater for your Amano shrimp aquarium, room temperature is usually sufficient.

How do amano shrimp behave in the aquarium?

Amano shrimps are not shy dwarf shrimps, but show their funny and interesting behaviour very freely. They are also not shy towards their fellow inhabitants – every now and then you may even see a cheeky amano shrimp stealing food from the mouth of a fish in the aquarium!

Amano shrimps do not really have much respect for smaller to medium-sized fish such as guppies, platies and the like, and they do not perceive them as predators.

The swim-loving amano shrimps are diurnal and make the tank unsafe especially during their mating swim. Amano shrimps are not suitable for nano aquariums!

Can amano shrimps be kept together in an aquarium?

It is possible to socialise the robust and lively amano shrimps (malicious tongues claim they are cheeky) with small to large peaceful fish. Other dwarf shrimps or snails also tend to be left alone.

With one exception, however: If female Amano shrimp suffer from protein deficiency, it is possible that they will grab other shrimp and even slow or careless small fish like young guppies – or go after snails. You can remedy this by feeding a balanced diet with a good proportion of vegetable and, if you like, animal proteins. Compared to other dwarf shrimp, Amano shrimp have quite respectable claws – stick a finger in the water and let your Amanos nibble on it, the plucking is clearly noticeable. They are also fast and agile, very skilful swimmers. Make sure you feed your amano shrimp well and in a balanced way, especially in a community aquarium.

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