Breeding Medaka rice fish is a fascinating adventure that gives you an up-close look at the wonders of nature. These small, colorful fish Japan are not only beautiful to look at, but also relatively easy to grow in your own aquarium. Whether you are a seasoned aquarist or just starting out in this hobby, the process from egg to adult fish remains special every time. In this article I will take you through all the stages of Medaka development and give you practical ones tips to be successful in breeding these special fish.

The journey of one Medaka starts with a tiny egg and ends with a beautiful, adult fish that can reproduce itself. Each stage requires specific care and attention, but with the right knowledge and preparation it is a very satisfying experience. Let's discover together how to give your Medakas the best start and help them grow into healthy, adult fish.

The fascinating journey of Medaka eggs

The adventure begins when a female Medaka fish produces eggs that are then fertilized by the male. What makes Medakas so special is that after fertilization the female carries the eggs on her abdomen for a while before depositing them on aquatic plants or other surfaces. This gives you as a grower a unique insight into the reproduction process. The eggs are transparent with a slight yellowish tint and have a diameter of approximately 1 to 1.5 millimeters. They are surrounded by small adhesive threads that help them attach to plants such as Java moss or artificial spawnmops.

The development of the embryo in the egg is really fascinating to follow. At a water temperature of about 25 degrees Celsius, it takes about 10 to 14 days for the eggs to hatch. During this period you can observe the development of the fish in the egg with a magnifying glass or loupe. You first see small dots that grow into eyes, and later you can even see the heart beating. It is important to place the eggs in a separate container to prevent adult fish from eating them. Use water from the main aquarium and ensure a constant temperature between 23 and 27 degrees Celsius.

Optimal conditions for eggs

To give your Medaka eggs the best chance of survival, there are a number of factors you should pay attention to:

Water quality:

• pH value between 6.5 and 7.5
• Water temperature of 24-26°C for optimal development
• Clean water without ammonia or nitrite
• Regular small water changes (10-20% every other day)

Prevention of mold:

• Remove unfertilized (white, opaque) eggs immediately
• If necessary, add a few drops of methylene blue to the water
• Ensure good water flow without blowing away eggs
• Check daily for mold formation

The hatching of the eggs

When the eggs are ready to hatch, you will see the little fish actively moving inside the egg. This is a sign that hatching will occur within a few hours. The newborn Medakas, also called larvae or 'fry', are about 4 to 5 millimeters long and still have a yolk sac on their abdomen. This yolk sac contains nutrients that nourish the fish for the first 2 to 3 days of its life. You do not need to feed them during this period, but it is important to keep the water clean.

Please note that the newborn fish are extremely vulnerable. They can be easily sucked up by filters, so use a sponge filter or protect the inlet of your filter with a fine gauze pad. The water depth in the rearing aquarium does not have to be great; 10 to 15 centimeters is sufficient for the first weeks. This makes it easier for the small fish to find food and saves them energy when swimming to the water's surface for air.

Growing up: the first weeks of your rice fish

The first weeks are crucial for the development of your young Medakas. Once the yolk sac is used up, the fish have to look for food themselves. This is the time when you should start supplementing. Infusoria (microscopic zooplankton) is the ideal starter food for the smallest fish. You can grow infusoria yourself by letting some hay or dried plant leaves rot in the sun in a pot of water. After a few days the water is full of these microscopic animals. Feed small amounts several times a day, because young Medakas have a fast metabolism and need to eat regularly.

After about a week you can switch to slightly larger food such as newly hatched brine shrimp or finely ground flake food. Artemia is particularly nutritious and promotes healthy growth and beautiful colours. You can buy brine shrimp eggs and hatch them yourself in a separate container with salt water. This may sound complicated, but with a simple brine shrimp breeding kit it is actually very simple. Many Medaka breeders swear by brine shrimp because it significantly accelerates the growth of the young fish. Variety in the diet is important, so combine different types of food for optimal results nutrition.

Growth phases and development

The growth of young Medakas occurs in several phases, each with its own characteristics:

Week 1-2: Larvae stage

1. Fish are 4-6 mm long
2. Yolk sac is absorbed
3. Start with active swimming and eating
4. Very sensitive to water quality

Week 3-4: Juvenile stage

1. Length of 6-10 mm
2. Fins continue to develop
3. First color pigments become visible
4. Swimming behavior becomes stronger and more confident

Week 5-8: Young fish

1. Length of 10-20 mm
2. Colors become clearer
3. Gender characteristics begin to become visible
4. Can be transferred to larger containers

Feeding schedule for young Medakas

A good feeding schedule is essential for healthy Growth. here's a practical overview:

Adult Medakas: care and maintenance

After about 8 to 12 weeks, your Medakas will have grown into young adult fish. They have now reached a length of about 2.5 to 3 centimeters and their colors are fully developed. This is also the period when you can clearly see the difference between males and females. Males have a longer and more pointed dorsal fin and anal fin, while females are rounder and fuller, especially when carrying eggs. From this moment on they can in principle start reproducing themselves, although it is wise to wait until they are fully grown for optimal health of the parents and the offspring.

Adult Medakas are relatively easy to maintain, but do require consistent care. They thrive best in groups of at least 6 individuals, with a ratio of 2 females per male being ideal to prevent stress on the females. An aquarium of at least 30 liters is suitable for a small group, but more space is always better. Medakas are active swimmers who like to stay in the upper layers of the water, so provide plenty of surface swimming space. They are peaceful fish that get along well with other small, peaceful fish species.

Optimal care of adult Medakas

Aquarium furnishings:

• Minimum 30 liters for a group of 6-8 fish
• Many plants, both floating and rooted
• Soft lighting or partial shade
• Calm water flow
• Temperature between 18-28°C (can be even cooler)

Power supply:

• Our high quality Medaka food as a base
• Live or frozen food such as mosquito larvae, artemia, daphnia
• Small insects (fruit flies are a favorite!)
• Feed 1-2 times a day, amount eaten in 2-3 minutes
• One fasting day per week is healthy

Water quality and maintenance

Good water quality is the basis for healthy Medakas. These fish are surprisingly adaptable and can live in a variety of water conditions, but stability is the most important thing. Perform a weekly water change of 20-30% and test the water values ​​regularly. Medakas can even be kept in unheated aquariums if the temperature does not fall below 15 degrees, making them ideal for outdoor ponds in the summer.

Ideal water values:

• Temperature: 20-26°C (optimal), can Tolerate 15-30°C
• pH: 6.5-7.5
• GH: 5-15°dH
• Ammonia: 0 mg/l
• Nitrite: 0 mg/l
• Nitrate: below 20 mg/l

Health and disease prevention

Medakas are generally robust fish with few health problems, provided you keep them in good conditions. prevention Is always better than cure, so pay attention to the following points:

Signs of a healthy Medaka:

• Active swimming behavior
• Good appetite
• Bright, vibrant colors
• Smooth, shiny scales
• Fully spread fins

Warning signs:

• Lethargic behavior or lying on the bottom
• Loss of appetite
• Faded colors
• Collapsed fins
• White spots or mucus formation
• Swollen stomach or bulging eyes

Bij de eerste tekenen van ziekte is het belangrijk om snel te handelen. Isoleer zieke vissen in een quarantainebak en verhoog eventueel de watertemperatuur licht (naar 26-27°C) om het immuunsysteem te stimuleren. Voeg aquariumzout toe (1 gram per liter) voor veel voorkomende problemen. Bij aanhoudende klachten kun je specifieke medicijnen gebruiken, maar lees altijd de bijsluiter zorgvuldig.

Voortplanting en de cyclus begint opnieuw

Wanneer je Medaka’s volwassen zijn, zal de voortplantingscyclus vanzelf beginnen, vooral in de lente en zomer wanneer de dagen langer worden. Vrouwtjes kunnen om de paar dagen eitjes produceren, wat betekent dat je regelmatig nieuwe eitjes zult vinden. Als je deze wilt opkweken, herhaal dan het proces dat we aan het begin van dit artikel hebben besproken. Sommige kwekers laten de natuur zijn gang gaan in een goed beplant aquarium, waar enkele jongen tussen de planten kunnen overleven. Voor een hogere overlevingskans is het echter aan te raden om de eitjes of de zwangere vrouwtjes tijdelijk te verplaatsen naar een apart opgroei aquarium.

Het kweken van Medaka’s kan verslavend zijn! Voordat je het weet heb je meerdere aquaria met verschillende kleurvariëteiten en ben je bezig met het selecteren van de mooiste exemplaren voor verdere kweek. Dit is precies wat de hobby zo leuk maakt: elk visje is uniek en het proces blijft fascinerend, ongeacht hoe vaak je het meemaakt.

Veelgestelde vragen over Medaka kweken

How long does it take for Medaka eggs to hatch?
At a water temperature of 24-26°C the eggs hatch after about 10-14 days. At lower temperatures this may take longer (up to 3 weeks at 18°C), at higher temperatures it may take longer (7-9 days at 28°C).

Can adult Medakas eat their own young?
Yes, adult Medakas will eat both eggs and newborn fish if given the chance. It is therefore important to isolate eggs or pregnant females if you want to rear the young.

What is the best food for young Medakas?
For the first few days they live off their yolk sac. After that, infusoria is ideal, followed by newly hatched brine shrimp from about a week old. This gives the best growth and health.

At what age are Medakas sexually mature?
Medakas can be sexually Mature as early as 8-12 weeks old, depending on diet and Temperature. for optimal health, it is better to wait until they Are 3-4 months old before allowing them to mate.

How many young can a Medaka female have?
A healthy female can produce a Cluster of 10-30 eggs every 1-3 days throughout the breeding season. this Can amount to hundreds of eggs per year per female