Japanese Rice Fish (Oryzias Latipes) : Youkihi Richfish Care, Feeding, Breeding

By Alberto Roy

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The Youkihi Medaka Ricefish morph is an uncommon and brilliant orange color of the Japanese Rice fish. It is one of the most adaptable and hardy fish in the world.

The Youkihi Medaka Ricefish (Oryzias latipes, var. The “Youkihi”, also known as the Japanese Ricefish (or Japanese Killifish), is a highly adaptable fish species. It has been selectively bred to this bright, orange variety.

This schooling fish is an important feature in any community aquarium. It also makes a great addition to a planted aquarium.

It is unclear whether this fish should be included in the killifish family. However, it has a similar behavior to other killifish. This subtropical fish can live in all water salinities, including freshwater and marine.

What’s Japanese Rice Fish?

Japanese Rice Fish 1

Ricefish are often dismissed as dull and drab. However, they can shine in a planted aquarium. These peaceful, calm schooling fish are an excellent alternative to Tetras and make a great addition to any community tank.

It amazes me when someone says they are bored with their aquarium hobby. They have kept all kinds of fish, and they don’t know what to do with them.

It’s amazing how far this is from reality! There is a limited amount of fish available in the local area, so it’s possible to overlook some truly interesting fish.

This group includes the fish we call ricefish. Although they might seem small and unassuming in a shop, once taken home and placed in a tank, their subtle beauty is immediately apparent. Their behavior changes and you will be captivated.

Youkihi Medaka Ricefish

Youkihi Medaka Ricefish usually occupies the middle or top of the water column. It can be paired with small, peaceful fish. It is small in size and compatible with dwarf shrimp.

Japanese Rice Fish 3

Smaller, more peaceful invertebrates are also good choices for tankmates. It is recommended to keep the Youkihi Medaka Ricefish surrounded by dwarf shrimp. You should also introduce the dwarf shrimp to your aquarium before you introduce the Youkihi Medaka Ricefish.

Youkihi Medaka Ricefish should be kept in groups of six or more. It will display its best natural behavior in large schools and will not pay much attention to other species.

This tank-raised fish can be very adaptable and hardy, but it needs clean, well-maintained drinking water in order to thrive. It will also display the best coloration and health in an aquarium with dark substrate, particularly where floating plants are present.

It is a very outgoing species, provided it has enough cover. It can be easily bred in an aquarium. A secure aquarium lid is essential for this species.

Although the Youkihi Medaka Ricefish is not picky, it will thrive on a variety of mostly omnivorous food.

Japanese Rice Fish 6

All types of high-quality flake foods, pellets and live, frozen or freeze-dried Artemia microworms, Tubifex and finely chopped bloodworms are accepted. The Youkihi Medaka Ricefish requires vegetable matter as part of its diet. It is not a problem for aquarium plants.

What we like about this fish:

  • Very small, beautiful orange color and very small size
  • Peaceful relationships with fish and invertebrates
  • Fish that are very active and visible in aquariums
  • Ideal for both planted and nano aquariums
  • Extremely tough


  • Temperature: 64deg F – 75deg F (18deg-24deg C), but it can at least temporarily tolerate a temperature range of 44deg F – 104deg F (66.7deg-40deg C).
  • pH: 7.0-8.0
  • KH: 9-19 dGH
  • For a school, the minimum tank size is 10 gallons. However, a larger aquarium would be more beneficial.


  • Omnivore. Accepts high-quality, frozen and dry foods in the right size. It is important to include vegetable matter.
  • Social Behavior: Peaceful, schooling/shoaling.
  • Origin: A tank-bred dog, but native to Japan, China Taiwan, Korea and Vietnam
  • Average adult size: 1.6 inches (4cm)
  • Average Purchase Size:.5 to 1 inch (1.3 to 2.5 cm).

Japanese Rich Fish Introduction

Oryzias Latipes, a Japanese rice fish, is one of the most beloved pet fish. They are also known by the Japanese killifish or the Medaka. They are small and beautiful.

Japanese Rice Fish 2

Their semi-transparent orange, gold or yellow color is what makes them unique. Some of them also have blue eyes. Since the seventeenth century, Japanese citizens have kept them in aquariums.

They have since spread to India, Pakistan, Vietnam, India, and Korea. The Japanese rice fish has an extended body and a back that resembles an arch.

Their bodies glow in darkness, which is one of their most striking characteristics. The moonlight and gold medaka are the most well-known types of Japanese rice fish. While the gold medaka has been around since antiquity, the moonlight medaka is a new breed.

The rice fields of Japan are home to the Japanese rice fish. This is the perfect place to find fish of the “Oryzias genus”. This is due to the absence of predators. The water temperature is also suitable.

These fish were recently used by scientists in experiments to develop biological traits. Scientists believe they can reproduce faster and more efficiently in outer space.

Although it is simple to raise and house these fish, they need a special environment in which to thrive. We will learn everything we can about these amazing creatures.

We will also be discussing all requirements, starting with the aquarium and ending with possible diseases.

Rice Fish Aquarium Requirements

The Japanese rice fish live together in groups. These groups are called schools. They can sometimes move alone or in pairs, despite this fact. These fish live in the natural habitat of Japanese rice pads.

Japanese Rice Fish 4

You will need to recreate this environment. Because of their small size, they don’t need large aquariums to live in. A tank must be at least 10 gallons in size. Sometimes, a bigger tank is better. They will have plenty of room to move around freely.

A good filtration unit is essential. A good filtration unit is essential for Japanese rice fish. It is better for the fish to be in clean water.

Because these fish are very mobile and can jump out of aquariums, a tight lid is necessary. You don’t want fish running around the aquarium.

To enrich the water with oxygen, it would be a good idea to put a spongey lid on the aquarium. If the lid is not providing the required air support, you can drill 1/4″ tubing or an air inlet.

A well-lit environment is also important for them. The Japanese rice fish live in rice paddies that have shallow water. They receive plenty of sunlight.

You can cover the aquarium’s substrate with gravel or sand. They can hide from the elements with small plants or driftwood. They would feel as if they were living in their natural environment with these accessories.

Rice Fish Water Parameters

Each fish group has a unique place to settle because of the differences between them. Two key factors in determining the water requirements are the durability and homeostasis.

Some fish only live in shallow waters. Others find comfort and pleasure living deep below the sea, where pressure is too high.

Japanese Rice Fish 5

The best water type for Japanese rice fish is brackish water. These fish are known to wander off the rice paddies into the ocean. They can also be found in rivers, so they can survive in freshwater.

They thrive in cold environments. The water temperature that is suitable for Japanese rice fish is between 64 and 75 degrees Fahrenheit. The water pH should be between 7.0 and 8.0. Keep the aquarium water moving slowly.

Rice Fish Tank Mates

When housing fish, it is important to ask yourself “Will these fish be capable of co-existing with each other?” You must choose species that are compatible with each other.

There are two types: omnivores or carnivores. The peaceful omnivores show no aggression or violence. Omnivores make up the majority of pet fish.

Some fish, however, are vicious predators and will hunt other fish to feed on them. These two types of fish can lead to disastrous outcomes if they are combined in an aquarium.

The Japanese rice fish are naturally peaceful and friendly. They are rarely aggressive. They can co-exist with many species.

Make sure that the fish are the same size as the Japanese rice fish.

These fish are small and weak. These fish might be considered food by larger fish, even if they are peaceful.

Any fish that is aggressive or larger than the Japanese rice fish are clearly a threat. They are able to live peacefully with some sea creatures like shrimps or snails.

Feeding Rice and Fish

The peaceful Japanese rice fish don’t eat other fish or feed on other fish because they are peaceful. They are omnivores. You can get them in the form of frozen foods and flakes.

You can sometimes feed them small vegetables or worms, and it won’t hurt them. Some live foods contain many nutrients that fish require. They should be fed at least twice daily.

While they may need nutrients from fresh food, their diet should not be solely dependent on this. These fish are primarily plant-eaters. Too much live food can cause them to lose their peaceful nature.

They would become vicious carnivores gradually and slowly. Ask your pet shop staff for information about the best way to care for these fish.

Rice Fish Diseases

The Japanese rice fish are not prone to getting sick easily. But that doesn’t necessarily mean they are immune to all diseases. All it comes down to how well you take care your tank.

Be careful about the type of water you use and the accessories that you put in your aquarium. You must ensure that your plants and gravel are clean. Dirt and bacteria could pose a threat to fish.

The good thing about Japanese rice fish is the fact that infection doesn’t occur immediately. If one or more fish exhibit unusual behavior, you can quickly notice it. You can stop the spread of infection.

To prevent future diseases, ensure that your water is clean. This includes changing the water frequently and maintaining a filtration unit. A healthy diet with all the nutrients they need is essential.

These fish are easy to handle and should not pose a problem for housing. They are an excellent choice for housing if you are a beginner. You just need to gather the necessary information and you are good to go.

Breeding of Rice Fish

The aquarium must have certain conditions to ensure that they can breed. The aquarium must have the correct water temperature, the right number and type of plants.

The plants attract the fertilized eggs from their female abdomens and nurse the baby fish until they hatch. After ten to twelve days, the baby fish should be fully grown.

It can be difficult to identify the gender of Japanese rice. You might be able differentiate them if you concentrate on the anal fins. Males have larger anal Fins.

Many people are curious about the nature of Japanese rice fish. As the person responsible for their lives, housing and raising them is an important responsibility.

Those who are just starting out in the field often have many questions and are anxious to find out what to do. We will now discuss some of these issues.

Is Japanese Rice Fish Aggressive?

Japanese rice fish are peaceful and do not display any signs of aggression. They tend to isolate themselves among the plants when they feel anxious or nervous and stay stable.

The Japanese rice fish are happy and full of life. They can be seen moving around the aquarium together or alone. It’s rare for them to act aggressively or violently towards one another, so it’s hard to see.

Does Japanese Rice Fish need a filter?

To survive, the Japanese rice fish need to live in certain environmental conditions. One of these conditions is either freshwater or brackish water. It is important to have a good filtration system installed because faucet water can be dangerous.

First, take a small amount of your tap water and do a TDS (totaldissolved solids) test. The result will tell you what type of filtration system you need.

A reverse osmosis system and deionization (RO/DI) is a system that purifies water from any harmful bacteria or other unwanted substances.

Does Japanese Rice Fish need a Heater?

The ideal water temperature for Japanese rice fish is between 64 and 75 degrees Fahrenheit. They thrive in cold environments. They can tolerate water with moderate temperatures.

But if the temperature of the aquarium is too high, then their internal organs won’t be capable to deal with it and they will eventually die. Installing a heater in an aquarium will speed up their death.

What’s the life span of Japanese Rice Fishes?

The Japanese rice fish has a life expectancy of around four years. The average lifespan of a Japanese rice fish is around four years.

You can ensure your fish live as long as possible by creating a replica of their natural habitat and ensuring that they have the right water temperature, pH, and nutrients.

It will bring a smile to your face to see these tiny creatures move around in the aquarium. Although they are very easy to care for, it is still a responsibility.

You have to be able to do the job. We hope you found this article helpful in understanding Japanese rice fish.

Background of Oryzias Latipes

The Oryzias genus is a fascinating and widely distributed group that includes just over three dozen species small fish. It spans from India to Southeast Asia to Korea, across the sea to Japan, through the islands of Indonesia, Malaysia and the Philippines.

Although they are most commonly found in freshwater, many species can also be found in marine and brackish environments. They move freely between these environments.

Although they are not related to killifish, they are schooling fish and small. They spend a lot of time near the surface eating insects. This is the same place that killies use in their habitats. Many killie keepers have taken to working with these species due to their similarity.

Naming of Oryzias Latipes

Because they can be found in shallow, flooded rice pads throughout their range, they are known as ricefish. This habitat is ideal for small fish species as it has plenty of warm water and a lack predators. It also offers many places to breed and plenty of food in the form small insects and their larvae.

Origins of Oryzias Latipes

Many of you will be familiar with O. latipes, also known as the Medaka. Although they are thought to have originated in Japan and can now be found in China, Korea, and Japan, Medakas may also have been found in China. Its popularity as a pet is probably the reason for this. This fact is documented as far back at the 17th century.

This beautiful golden morph has been created by breeding it to the original creamy-white fish.

Scientific Uses of Oryzias Latipes

They are used frequently in scientific research. They currently live in an aquarium at the International Space Station.

They are also at forefront of genetic research. Hobbyists in certain countries have access to a transgenic, green, glowing version. O. latipes, along with the zebra danio Danio rerio, is probably the most studied vertebrate species worldwide.

In The Hobby

Many hobbyists would dismiss ricefish as too dull if they saw them in a shop. Even the most drab species can still have stunning, bright-blue eyes that draw attention from far away.

Many ricefish have attractive patterns, with a few exceptions like the neon-colored O. woworae (O. woworae) which is quite spectacular.

Most species are smaller than 2 inches. Many species, including the tiny Mekong ricefish O. mekongensis (O. mekongensis), measure just an inch or less.

The island of Sulawesi seems to have the real giants of the genus. There are many species that exceed 2 inches, and one, the yellow fin ricefish (O. profundicola), which reaches almost 2 1/2 inches.

Aquarium Care of Oryzias Latipes (Chinese Rice Fish)

Ricefish are adaptable because they can be found in many species over large areas, with saltwater often separating their freshwater habitats. The Medaka (O. ltipes), is found in Japan and Korea.

However, recent research suggests that O. latipes may actually be a complex species of many species. From Java, all the way to Thailand, the Javanese ricefish (O.javanicus), can be found!

Water Requirements of Chinese Rice Fish (Oryzias Latipes)

This is great news for hobbyists as they can usually adapt to tap water without having to remove chlorine or chloramines. Instead, we can concentrate on making large, frequent water changes to reduce dissolved pollutants.

Hobbyists who keep killie plants in small tanks often have them in clumps of Java moss and Java fern. They are often kept in small tanks with no filter.

This is as long as they are fed healthy foods and get regular water changes. If they are kept in pairs, they will thrive and even reproduce in smaller tanks than one gallon. This makes water changes and care easy in these smaller tanks.

In small tanks, the most important thing is to stock light and keep the water clean. Although it is difficult to maintain temperature in small tanks due to their limited size, most species aren’t too picky about temperature.

It is possible for them to be comfortable as long as they are in the same room. For most species, temperatures in the 70s are ideal.

Cover Your Tank

It is important to remember that ricefish can jump very well so it is essential that the tank is covered. It is possible to place a sponge filter inside the tank to provide biological filtration and oxygenation.

If the lid is not equipped with a punch-out, drill 1/4 inch holes in it and then run the airline tubing through the hole. You can cut a glass top at one corner to allow for the airline. Any excess space can then be covered with packing tape.

Community Life

They thrive in small-sized fish community tanks where they can be model residents. They will appreciate the plants and large swimming areas in front of them. They are most often found in areas with low current, so it is important to keep them in tanks that don’t require strong filtration.

Ideal is a sponge filter or canister. A group of about a dozen fish will enjoy a large tank with a sponge filter or canister.


Ricefish, which are wild-caught, are omnivores. They eat everything, from biofilm to insects and fish eggs to whatever is available in their area. Friends in Japan have reported that flake food can be eaten by wild fish.

They can eat high-quality pellet and flake foods. For several days, you can offer live foods such as fruit flies, daphnia and newly hatched brine shrimp to your fish. If you have other live foods available, they can be greedily eaten.

Breeding of Rice Fish (Oryzias Latipes)

Most species have easy sex. The females tend to be a little larger than the men. Depending on the species, males can be a little more colorful than females. Many species have males with anal fin extensions, which can be quite impressive in certain species.

The body of females tends to be larger than that of males. The genital papilla is a small bump that appears in males just in front of their anal fin. This area is typically flat for females with a small protrusion.

Many times, even in community tanks, you can see females swimming with clusters of eggs in their mornings. This is one of the most fascinating things about ricefish.

Reproductive Behavior of Oryzias Latipes

Scientists continue to study their reproductive behavior. In many species, however, this is not yet known. The observations have shown that males have one, pointed, tubular, genital papilla, while females have two, flattened, round, lobular, genital papillae.

Some species also have thickened anal fins that are thought to be used for mating. Other species have males with small contact organs located on the back and middle rays of their anal fins that can also be used for mating. In most Oryzias species, the males fertilize the eggs internallly.

Eggs of Oryzias Latipes

The mating process takes place almost every day for several months. After that, the fish rest for a while before starting again. For several days, the fertilized eggs are inside the female. She can lay up to 20 eggs each day in the early morning.

Thin filaments keep the eggs close to the female’s vent. This makes it appear that she is swimming with grape clusters attached. The eggs attach to or fall to the ground, and she swims through fine-leaved leaves.

The developing embryos are left to their own devices. The eggs can hatch within a few days depending on their species.

Only a few open water species, like O. sarasinorum or O. eversi (which are found in streams and lakes on Sulawesi), have a female with extended pelvic fins. These form a protective pouch around the eggs, and she actually carries them until they hatch.

It can take up to 18 days for the eggs to reach this point after they have been laid. These species have a female that forms a notch in the abdomen cavity and the front of the anal fin to hold the eggs in their place.

It is amazing to me how the eggs of O. mekongensis, a small species, and O. celebensis, a large species, are almost identical in size. It’s not surprising that this group will see more unusual reproductive behaviors as more species are investigated.


Although well-fed adults are less likely to eat fry than their smaller siblings, larger siblings may consider their younger siblings to be a tasty morsel. It’s best to separate fry from fry that have more than one week of age.

When fry hatch, they are ready to eat. Good first foods include vinegar eels or microworms. Many species of fry will also eat fine-powdered prepared fry meals.

They grow quickly and will soon be able take freshly hatched brine shrimp within a week. Many species can spawn when they are only three months old.

They live only one year in the wild and are therefore likely to have adapted to a shorter lifespan and being at the bottom of the food chain.

They can live up to five years in our aquariums, where they are well-fed and sheltered.

How do I breed them?

For most of the year, I keep my specimens in mixed species tanks. They are fed a high-quality flake of food or floating micropellet foods every day. I add live food to the tank several times per week: daphnias, brine shrimps that have just been hatched, various worms and flour beetles.

When I want to get my spawn, I change from one to many pairs to a 5- to 10-gallon tank. A 3-gallon critter tanks is perfect for smaller species.

No matter what size tank you use, make sure to keep the lid on! I add a few spawning mop or fine-leaved plants to my tank and feed the adults with plenty of live foods.

Water Filtration

Although I add a sponge filter to my tank, it isn’t always necessary. Sometimes, I just add a bubbling airline to my tank. I simply change the water every two days by pouring half the water out through the holes in the lid, and then refilling.

I feed them live food like daphnia, small worms and other types of small worms at least twice a day. After two weeks, the adults are returned to the main tank.

Eggs and Fry

The eggs will hatch over the next few days. The tiny fry can be found just below the surface. The fry should be fed from the beginning. The fry can have the daphnia as soon as they are born, but I do not leave them in the tank.

You can feed them vinegar eels or microworms from the beginning. They can eat newly hatched brine shrimp within a week, as I have mentioned.

They grow quickly and can reach 3/8 inches in length after two to three weeks. For their growth, I transfer them to a 10-gallon aquarium.

I don’t net fry. Slowly, I transfer them from the hatching tanks to this tank. To help with cleaning up excess food, I add small ramshorn snails at this stage.

Snails can be eaten by eggs so I don’t keep them in the spawning tanks. For the next few weeks, I will be doing water changes every day.

Moving Tanks

Three pairs of fry can produce hundreds of fry in a couple weeks. It is possible to move them around to bigger tanks over time. They will reach 1/2 inch in length after a few weeks. Then I transfer them to a 30-gallon tank in my fishroom where they will remain until they can go out on their own.

Surprisingly for something that some people consider bland fish, they are almost always in high demand and I have no problem finding new homes.

I don’t raise many species. I have a small number of them, and I don’t want to flood the market. Although one could theoretically raise thousands of animals, it would be difficult to find homes for that many.

It is better to just enjoy these fish and to breed enough to sustain them.

A Pretty Little Fish

Although they are often overlooked, the members the fascinating group known as ricefish can make interesting additions for aquarium hobbyists. Even the most skeptical viewer will be drawn to a school of them in a communal tank.

You have a winning combination of aquarium fish that are easy to care for, exhibit model behavior, and interesting methods of reproduction.

If you are looking for something different and unique next time that you visit your local fish shop, look no further than the ricefish. They’ll make you happy that you brought them home.

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