Breeding and Life Cycle of Amano Shrimp

Amano shrimp (Caridina multidentata) is one of the most popular species of freshwater dwarf shrimp that is commonly kept as aquarium pets. But, if you want to know more specifically about the breeding and life cycle of these shrimp, you have come to the right place.

On the whole, Amano shrimp go through 12 distinct life stages. They start as eggs and progress from being larvae (9 zoea stages), into being juvenile, then to being adult shrimp. It takes them around 40 days to reach the juvenile stage and another 90-120 days to become adults.

These shrimp have an amphidromous life history. It means that adult Amano shrimp live and reproduce in freshwater environments, whereas the development of their larvae takes place exclusively in seawater. 

Keep reading for everything there is to know about the breeding and life cycle of Amano shrimp. I will go into detail on every aspect of their life and breeding procedures.

I need to start off by saying that, in this article, I will not be talking about how to care for Amano shrimp. If you need this kind of information, read my guide on this species.

Part one: Life Cycle of Amano Shrimp

Mating:

The life cycle of Amano shrimp starts with mating. Although mating itself is a very brief process (a few seconds), it can be done only when the female is ready.

1. A mature female picks up eggs in the paired ovaries, in which the eggs are produced. The paired ovaries are located at the junction of the cephalothorax (carapace) and the tail (abdomen). In Amano shrimp, it is very easy to see them because the shrimp are Generally, for a characteristic location and a special form, the paired ovaries aquarists usually call a “Saddle”.
2. Female has to molt (shed their old exoskeleton) prior to mating, which makes fertilization possible.
3. Next, the female releases a certain chemical substance (pheromone) into the surrounding water to attract males. This signals the males that she is ready to spawn. It will cause the males to go into a frenzy to find her and breed with her.
4. During mating, the males need to find at a right angle and transfer the spermatophore to a specialized receptacle on the female’s abdomen.

Insemination:

Amano shrimp have external fertilization.

After molting, females become flexible enough to transfer the eggs (squeezing) from the “saddle” to the brood pouch. At that moment the eggs go through the spermatophore and become fertilized.

Stage # 1 – Eggs

After fertilization, the eggs remain attached to the female’s swimming appendages (called pleopods). Amano shrimp use pleopods to keep the eggs clean from dirt and well oxygenated.

The size of the females positively correlates to the number of eggs they can carry. Large females have more eggs.

Caridina multidentata belongs to the small egg group and bears many eggs. Eggs are oval in shape and of dimensions 0.50×0.31 mm (after spawning) and 0.54×0.35 mm (before hatching).

Amano shrimp have high fecundity. According to the study, Caridina multidentata can have anywhere between 747-4391 eggs per brood (an average of 1872 eggs). 

Note: By the time of hatching, females lose most of their eggs. This is because the increase in egg volume caused by water uptake limits the availability of egg carrying space, resulting in smaller broods. Therefore, even large females usually have only a few hundred eggs (200 – 400 eggs).

Females hold the eggs until hatching day. Depending on the temperature, Amano shrimp usually carry them for 4 – 5 weeks. For example, fertilized eggs took about 25 days to hatch into larvae at a water temperature of 78 F (25.5 C)

If you can see the eyes of the developing embryos through the eggshell, it means that the eggs will hatch within several days.

Note: Male shrimp do not exhibit parental care for their offspring in any way.

Stage # 2 – 10 (Hatchlings and 9 Zoea stages)

After hatching, they have planktonic larval stages. Basically, they have to go through 9 stages before reaching adult body form. 

Note: Zoea are the free-swimming larvae of aquatic decapod crustaceans 

Zoea stages	Size (total length)	Period
First	1.55 (1.48-1.76) mm.	to 10 days
Second	1.76 (1.59-1.93) mm.	4 to 13 days
Third	2.10 (1.82-2.35) mm.	6 to 14 days
Fourth	2.10 (1.82-2.35) mm	10 to 18 days
Fifth	2.21 (1.89-2.75) mm	12 to 22 days
Sixth	2.76 (2.42-3.10) mm.	14 to 29 days
Seventh	2.95 (2.81-3.24) mm.	15 to 31 days
Eighth	3.90 (3.59-4.32) mm.	16 to 33 days
Ninth	5.01 (4.77-5.35) mm.	22 to 35 days
The first juvenile	4.83 (4.60-5.20) mm.	24 to 38 days

Note: Caridina multidentata does not have megalopa stage. In science, the megalopa is called an intermediate stage between the planktonic (zoea) and the final form of the animals.

Stage # 11 – Juvenile (Growing)

Baby Amano shrimp are pretty small but will grow very quickly. In the natural environment, being small is a huge danger, they can fall prey to almost everything.

At this stage, shrimplets require a lot of nutrition. However, in the matured aquarium, it should not be a problem. In addition, like adults, Amano shrimplets are not picky eaters as well.

They can eat the same food as adults. It just needs to be in smaller proportions. This is an important step in their life.

11.1. Molting (Growing)

Amano shrimp have a hard multi-layered exoskeleton (shell) that protects their internal organs and prevents their growth. However, exoskeletons do not grow as the animal inside them grows. Therefore, they are forced to molt (shed the old exoskeletons) as they grow bigger.

This process is characterized by a complete replacement of the old mineralized exoskeleton with a new one.

The frequency of molt depends on age and temperature. For example, very young Amano shrimp can molt every few days, whereas juveniles usually molt every 1 to 3 weeks. Fully grown shrimp molt every 1 – 2 months. Generally, they do that to restore lost limbs.  

Recently molted shrimp are extremely susceptible to attacks from other animals

Important: Calcium (Ca) is an essential component of the exoskeleton composition. So, growing a new exoskeleton requires a high amount of Ca to facilitate calcification. The process of molting puts shrimp in a vulnerable state.

Related articles:

• How to Supplement Shrimp and Snails with Calcium
• Aquarium: Molting Process and Metabolism of the Dwarf Shrimp

Stage # 12 – Maturation  

In Amano shrimp, the juvenile stage can be defined as a period before it meets reproductive maturity.

Once the reproduction system starts developing, Amano shrimplets turn into adults. Generally, it takes them about 3 – 4 months to become mature.

From that moment it is possible to differentiate males from females with the naked eye. This completes their life cycle and starts a new one.

Related article:

• Shrimp Gender. Female and Male Difference

Part two: Breeding Amano Shrimp

The adult Amano shrimp live and reproduce in freshwater environments. However, their zoea (larvae) need brackish water in order to survive.

The zoea of this species hatch as a planktonic stage. In the natural environment, they are swept by water flow and passively drift into the ocean where they develop. After metamorphosis, juveniles migrate upstream to freshwater habitats from which they originally came.

Replicating this process in home aquariums is not that easy. That is why almost all Amano shrimp are wild-caught.

Setup for breeding Amano shrimp (some links to Amazon):

• 1 – 2 gallon (4 – 10 liters) breeder tank for rising Amano zoea.
• A few 1 – 2 gallon (4 – 10 liters) bottles for culturing Tetraselmis sp. (food for Amano zoea)
• Instant Ocean & Reef Crystals Reef Salt
• Refractometer.
• Turkey baster (or a big syringe).
• Aquarium Saltwater test kits.
• Lid and Light
• Flexible airline tubing
• Air pump (optional)
• Check valve (optional)

1. Rearing Tank

Some aquarists say that there is no need to prepare the rearing tank in advance.

Nonetheless, I noticed that the survival rate was much lower if I did not prepare anything beforehand. This is probably because of a combination of 2 factors:

1. It does not stabilize your water parameters.
2. It does not give phytoplankton and algae enough time to start growing in the rearing tank.

Therefore, I would still recommend doing it beforehand. So, prepare the rearing tank a few days before you are planning to transfer Amano zoea into the tank.

Note: There is no need to have a large tank to raise Amano zoea. A 1 – 2 gallon (4 – 10 liters) breeder tank will be more than enough.

2. Preparing Saltwater

The next step is adding sea salt.

Important: Do not ever use simple aquarium salt or table salt to prepare saltwater! It will kill Amano zoea.

You can use only special marine salt (such as Instant ocean marine salt or similar).

According to the study, Amano shrimp larvae exhibited an ability to adapt to a wide range of salinity conditions (17 – 34 ppt or 1.0128 – 1.0256 SG). However, most aquarists, including myself, had a better success rate at 30 – 35 ppt (or 1.0226 – 1.0264 SG).

So, our goal is 32 ppt (1.0241 SG). For that, you will need a refractometer to take accurate measurements. Keep the temperature range between 71 – 79 F (22 – 26 C) as well.

1. Add marine salt into the water.
2. Stir the water properly for a few minutes.
3. Let it sit for about 20 – 30 minutes.
4. Stir again to ensure that the salt is entirely dissolved and evenly distributed.
5. If the salinity level is high, add more freshwater, and if it is too low, add more marine salt mix.

Should you use RO water or old aquarium water?

Both options are viable. Each has pros and cons.

Old aquarium water already contains microorganisms that will boost the growth of phytoplankton and algae in the rearing tank. On the downside, you cannot be absolutely sure that there are no things that can harm Amano zoea.

On the contrary, with RO water, you will be able to define all parameters to your own specifications. However, it will take longer to establish phytoplankton and algae in the rearing tank. 

How much saltwater do you need in the rearing tank?

I would say that 3 – 4 inches (7 – 10 cm) will be enough. Do not fill the rearing tank all the way.

Actually, it will be counterproductive. In shallow tanks, Amano zoea will have more oxygen. Whereas in the deep tank, you will definitely have to use air pumps.

Note: Air pumps are dangerous to Amano zoea. I will be talking about it later.

3. Preparing Food for Amano Zoea

This is the most important step. I will repeat it again – THE MOST!

You will need cultured phytoplankton Tetraselmis sp. (link to Amanon). Tetraselmis sp. ia  green unicellular algae with 4 distinct flagella. The algal cells of cultured Tetraselmis can move around freely in seawater.

According to the study,  only cultured Tetraselmis can sustain larval survival and development to the juvenile stage in Amano shrimp. Even preserved Tetraselmis do not have the same efficiency.

Do you need to give Amano zoea anything else?

No, you don’t. Amano larvae will be absolutely happy with cultured Tetraselmis until they become juveniles.

This is one of the rare cases when there is no need to diversify their diet. Even more, giving them more food will only risk spoiling the water quality.

3.1. Option # 1 (recommended)

1. Take a few 1 – 2 gallon (4 – 10 liters) bottles for culturing phytoplankton (Tetraselmis).
2. Add saltwater.
3. Add algal 
4. Provide 24 hours of light.
5. Add Tetraselmis into bottles.
6. In 2 – 3 days you will see that your water become greenish. This is exactly what you need. Tetraselmis is growing.

Now you can add some Tetraselmis into the rearing tank (1.6 oz per 1.5 gallons or 50 ml per 6 liters).

3.2. Option # 2

1. Some breeders do not exactly feed the Tetraselmis to the Amano zoeas. Instead, they drop the zoea directly into the algal culture.

The drawbacks of this method include:

• Risk of losing the Tetraselmis culture will lead to the death of Amano larvae. Do not put your eggs in one basket.
• Uncontrollable growth rate may reduce the oxygen level in the rearing tank.
• Tetraselmis also require food (fertilizers) to reproduce. By adding fertilizers into the rearing tank, we can spoil water quality.

When do we need to prepare food for the Amano larva?

The Tetraselmis should be cultured at least 3 – 4 days before the Amano larva appear.

Important: some people make a simple mistake, which can kill Amano larvae. They provide 24 hours of light but they do not do it in advance. As a result, algae do not have time to grow and larvae die without enough food.

Should I feed Tetraselmis? How to feed Tetraselmis?

Tetraselmis also need food to reproduce.

If you are using old tank water (from water changes), it may already have enough nutrients for Tetraselmis. If you are using RO water, you will need to use any hydro fertilizer for that.

Note: Although there are some special algal fertilizers (link to Amazon), we do not have to buy them.

Related article:

• How to Culture Phytoplankton

4. Hatching day

When you can see the eyes of developing embryos through the eggshell, then the eggs will hatch within a few days.

Interesting fact: The embryos do not hatch all at once. Some of them start hatching 3 – 5 days before the main group. It will also give you an idea of when to be extra vigilant.

Tip: To trigger the process, do a 25 – 20 % water change.

There are two options here:

• First. When the female is about to hatch, you need to move her to another tank. After hatching, return her to the main tank.

Important: Use only freshwater. Do not put adult Amano shrimp into saltwater. They do not tolerate it.

• (recommended) If you do not want to mess with the separate tank for the female. Leave everything as it is.

The eggs hatch at night. Because of their small size, the hatchlings (zoea) can be easily sucked into the filter.

To avoid this from happening, you need to lower (turn off if possible) your filtration and place a desk lamp on the opposite side of your filtration.

Amano larvae are highly sensitive to light. It attracts them.

5. Transferring Amano larvae

In the morning, use a turkey baster or a big syringe to catch the Amano larvae. Move them into the rearing tank.

Amano larvae do not require a slow transition into the saltwater. Just drop them there.

During the first few weeks larvae swim in a heads-down position. They are almost transparent and barely visible. Keep in mind that the larvae must go into saltwater within 2 – 3 days or they will all die. Starting from the 4^th day you will lose 10-15% of larvae until they all die within 7-10 days.

6. Feeding Amano larvae 

According to the study, Amano larvae start to take food at stage 3. They are potentially lecithotrophic. So, we do not have to feed them during their short stay in freshwater.

Note: Lecithotrophy means feeding on egg yolk or other materials put in the egg by the mother. 

After that, larvae will need Tetraselmis to grow. Therefore, it should already be in the water.

7. Changing salinity   

After 4 weeks you will notice a slight transformation in Amano larvae. So, during the next water change, you can start lowering salinity to 20 – 25 ppt (1.015 – 1.0188 SG).

7. Transferring Amano larvae into freshwater   

After 40 – 45 days, Amano Shrimp larvae will complete transformation into actual Amano shrimp. From this moment, they are tiny copies of adult shrimp. It means that they cannot tolerate elevated salinity levels anymore.

You will see them swimming only forward (larvae can swim in all directions).

So, if you see that they are swimming like crazy non-stop, it means that they are ready to go into your main aquarium. In nature, this behavior says that juveniles are trying to migrate up to the adult freshwater habitat.

Tip:  do not do any sudden transitions from saltwater water to freshwater. Replace half of the saltwater water with your aquarium water for 1 day. Let them accustom a little bit to the new water conditions. After that, drain the water in the bowl down to the bottom. So it will be easier to put them into the main tank.

FAQ about breeding Amano larvae.

The larvae float to the surface and stick to the bacterial film. What should I do?

Generally, this problem arises during the first 3 weeks when larvae are weak and cannot control their movement. The larvae periodically float to the surface, stick to the bacterial film and die. There are several ways to avoid this      :

• Manually remove the bacterial film. Float a piece of paper over it for a few seconds. Lift the paper off and you will notice that all that protein film sticks to it. Do the same using another side of the paper. Throw away that piece of paper and take another one. Do not reuse it.
• Manually drown larvae. Use a dropper, a turkey baster, or a syringe. Just drop by drop.
• Do water change.
• Increased circulation and airflow. So, a surface film will not form.

Do I need aeration in the rearing tank?   

Strictly speaking, in shallow tanks, aeration is not necessary.

However, if your rearing tank is almost completely filled with water, you will need some aeration. Avoid too much aeration. It should not spin the larvae throughout the tank.

Where should I put the lighting?   

It was noticed that having lighting on top reduces biofilm formation. Thus, Amano larvae do not stick that often.

Do I need filtration in the Amano rearing tank?

No, filtration is not necessary. Amano larvae do not produce a lot of waste.

In addition, filters may suck in tiny larvae.

Note: I used to use filters filtration before. Now I have changed my opinion because of the better survival rate. 

How often should I do water changes?

Generally, your first water change (10 – 15%) will be after first week. After that, you need to do it every 2 – 3 days.

However, if you can barely see the opposite side of the tank due to the excessive growth of Tetraselmis, it would be better to do a large water change. Just do not forget to lure larvae to the corner of the tank.

Also, check your water level. Evaporation will increase the salinity, it will affect larvae.

Note: It is possible to breed Amano larvae even without water changes but it will significantly reduce the survival rate.

Why do I have problems with Tetraselmis?

Some potential problems why Tetraselmis may die out include:

• They do not have enough food. Use fertilizer. Be careful with overdosing, it can also affect their growth rate.
• High and low temperature may kill Tetraselmis.
• The lighting is too strong or too much. I would recommend short light breaks (for at least 3 – 5 hours).

What is their survival rate?

There is a reason why Amano shrimp have a high fecundity (an average of 1872 eggs). Unfortunately, only a few dozen larvae will survive even if you do everything right.

In Conclusion

The lifecycle of Caridina multidentata, also known as Amano shrimp, is typically divided into 12 stages: eggs, zoea (9 stages), juveniles, and adults.

Females carry eggs under the abdomen. Depending on the temperature, the incubation period lasts 4 – 5 weeks.

Amano shrimp develop for a relatively long period (40 days) with complex zoeal stages. After multiple molts (growing curves), they reach sexual maturity in 3 – 4 months and become adults.

Breeding Amano shrimp in captivity is difficult but possible. Multiple experiments have revealed that feeding conditions, temperature, and salinity are the most important factors affecting larval survival.

References:

1. 曹林泉, 秦政, 姜玉声, 刘鑫, 李晓东, 林源, 黄楷涛, and 刘胥. “Embryonic Development of Caridina japonica and in vitro Incubation of Its Fertilized Eggs.” PROGREES IN FISHERY SCIENCES 41, no. 1 (2020): 145-152.
2. Hayashi, K. I., and Tatsuo Hamano. “The complete larval development of Caridina japonica De Man (Decapoda, Caridea, Atyidae) reared in the laboratory.” Zoological Science 1, no. 4 (1984): p571-589.
3. Hamasaki, Katsuyuki, Sota Nishimoto, Masakazu Okada, Asahi Kimura, Kosei Otsubo, and Shigeki Dan. “Dietary effects of phytoplankton and zooplankton on larval survival, duration and growth of four Caridina species (Decapoda: Caridea: Atyidae) under laboratory conditions.” Crustacean Research 49 (2020): 225-237.
4. Kondo, Shuji, Katsuyuki Hamasaki, and Shigeki Dan. “Larval performance of three amphidromous shrimp species in the genus Caridina (Decapoda: Caridea: Atyidae) under different temperature and salinity conditions.” Crustacean Research 50 (2021): 41-54.
5. Klann, Marleen, and Gerhard Scholtz. “Early embryonic development of the freshwater shrimp Caridina multidentata (Crustacea, Decapoda, Atyidae).” Zoomorphology 133, no. 3 (2014): 295-306.