The Medaka Library
Everything I've learned raising Japanese rice fish, written down so your fish thrive from the day the box arrives. No fluff, no filler, just what works. These are my methods, proven in my own pots. Other keepers succeed in their own ways, and that variety is half the fun of this hobby.
49 guides
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Start here
New to medaka? These cover what they are, whether they suit you, and how to set up.
What Are Medaka?
Japanese rice fish, Oryzias latipes. Where they come from, why the rice paddy explains everything about them, and who they suit.
Read the guide →What Does Medaka Mean?
High eyes, a rice-field Latin name, over 4,600 local nicknames, and a song every Japanese child knows. The history inside the word.
Read the guide →Why Buy From a Small Breeder?
The price tag is not the whole price. What a chain-store fish comes without, and what to look for wherever you buy.
Read the guide →The Best Gift for a Fish Lover
Why a surprise fish usually backfires, and the version that lets them pick their own fish for the day their water is ready.
Read the guide →Why Are Medaka So Expensive?
A feeder guppy costs next to nothing. Where the difference actually goes: generations of line work, hand-sexing, and shipping a live animal well.
Read the guide →Medaka as a First Pet for Kids
Hardy enough to survive a beginner, alive enough to teach real things. What a tub of fish gives a kid, and the parts parents should know first.
Read the guide →The Easiest Pet
No walks, no vet bills, no heater, and no crisis if you skip a day of feeding. The full case for medaka, fine print included.
Read the guide →Best Fish for an Outdoor Tub
Medaka, white clouds, guppies, goldfish, or a mosquitofish? How the common choices hold up in a patio tub, summer through winter.
Read the guide →Giant Duckweed: Benefits and Drawbacks
Duckweed has a bad name. What is fair, what is not, and whether giant duckweed is really a great plant for filtering water.
Read the guide →Drying Duckweed Into Fish Food
Farms feed it to fish worldwide. What the research shows, how to dry it safely, and what nobody has tested in medaka.
Read the guide →Normal, Hikari, and Daruma
Body type is not the same as colour. What each shape looks like, how to tell them apart at a glance, and which ones need more care.
Read the guide →Medaka Varieties, Explained
Miyuki, Youkihi, Orochi, lame, and sanshoku in plain English, and why US trade names don't match the Japanese ones.
Read the guide →Medaka in Science
A genetics pioneer since 1921, the first vertebrate to mate in space, and a genome milestone. Your pond fish has a resume.
Read the guide →Medaka Care: The Complete Guide
Tank and tub setup, water, temperature, feeding, tankmates, and the first 48 hours after your fish arrive. Start here if you're new to this hobby.
Read the guide →Your Medaka Just Arrived
The box is here. Floating, acclimating, and releasing shipped fish step by step, and what is normal in the first 48 hours.
Read the guide →Medaka vs. Goldfish, Koi, and Guppies
Planning a patio pond or tub? A practical comparison of size, waste, and cold-hardiness, and why goldfish outgrow a small pond that medaka fit perfectly.
Read the guide →How Many Medaka Can You Keep?
Real stocking numbers for tanks and tubs, why surface area matters more than gallons, and why you should leave room for fry.
Read the guide →Medaka Lifespan and Life Stages
How long they live and what to expect at each stage, from egg to breeding adult to an older fish that has slowed down.
Read the guide →Setup and equipment
What you actually need, and the two things most people buy that medaka do not require.
The Walstad Method
Dirt, sand, plants, water, fish, and almost no equipment. The natural planted method that matches how medaka actually live, and why my pots run on the same idea.
Read the guide →Do Medaka Jump?
Yes, and it is one of the most common ways beginners lose a fish. When the risk peaks, and the freeboard rule that prevents nearly all of it.
Read the guide →Do Medaka Need a Filter?
Often not. When plants do the job instead, when a filter earns its place, and why a sponge filter is the right one to use.
Read the guide →Do Medaka Need a Heater?
Short answer: no. Why these temperate fish thrive without one, what actually protects them in winter, and the one time warmth is worth considering.
Read the guide →Fish That Eat Mosquito Larvae
Set up a medaka tub and it doubles as mosquito control, eating the larvae before they hatch into biters, a beautiful alternative to the classic mosquitofish, which is restricted in some places.
Read the guide →How Hot and How Cold Can Medaka Go?
The band they are comfortable in, what they merely tolerate, the danger zones at each end, and why the rate of change matters more than the number.
Read the guide →How to Build a Medaka Mini Pond
You bought the planter, now what? Container, water, plants, the patient two weeks, and the fish. No electricity required.
Read the guide →Keeping Medaka Indoors vs. Outdoors
Both work. What actually differs is light, live food, breeding season, predators, and winter, plus how to move fish outside safely.
Read the guide →Keeping Medaka Outdoors Year-Round
Patio tubs, mini ponds, and overwintering. How medaka handle heat, cold, and everything between, and why outdoor fish show their best color.
Read the guide →Medaka vs. Mosquitofish
Both eat larvae. Temperament, looks, and what happens if they escape are where the two fish part ways.
Read the guide →Medaka Water Parameters
What pH, KH, ammonia, and nitrate actually do, which numbers matter, and why stability beats perfection.
Read the guide →What Your Water Test Results Mean
You tested, now you have numbers. Which readings are emergencies, which can wait, and the calm plan for each.
Read the guide →Winterizing a Medaka Tub
No heater needed. When to stop feeding, what depth actually does, how to handle ice, and the interventions to skip.
Read the guide →Feeding and tank mates
Day to day keeping: what goes in the water with them, and what goes in their mouths.
What Can Live With Medaka?
Shrimp and snails yes, most fish no. The two questions that settle every case, and why I keep mine with snails and nothing else.
Read the guide →What Do Medaka Eat?
Pellets, live food, and mosquito larvae. How often to feed, how much, feeding fry, and what changes as the water cools.
Read the guide →Breeding medaka
Getting eggs, hatching them, raising fry, and what to check when a group stops laying.
Breeding Medaka for Color
How selective breeding actually works: keeping a line true, what crossing does, and what to realistically expect per generation.
Read the guide →Breeding Medaka with Spawning Mops
Conditioning breeders, collecting eggs, raising fry, and why a simple yarn mop out-performs almost everything else for egg collection.
Read the guide →How to Sex Medaka
Male or female? The anal fin answers it at a glance once you know the two shapes. The clues that only sometimes help, and when fish are old enough to call.
Read the guide →How to Tell If Medaka Eggs Are Fertilized
Clear means good, chalky white means gone. What to look for, when eyes appear, and why removing the bad ones protects the rest.
Read the guide →Medaka Fry Care
Hatching eggs, first foods, and the two mistakes that cause most fry losses in the first fortnight.
Read the guide →Methylene Blue, Demystified
The old blue bottle: what it does for hatching eggs, whether you need it at all, and why it never touches the main tank.
Read the guide →Why Are My Medaka Not Laying Eggs?
Daylight, temperature, sex ratio, age, and condition. A breeder's checklist, in the order worth working through.
Read the guide →Health and troubleshooting
Hair Algae, Handled
Green threads winding through your plants? Twirl them out with a toothbrush, then fix the light and nutrients so they stay gone. No chemicals.
Read the guide →Is My Medaka Sick?
Clamped fins, white spots, fuzzy patches, or a fish that stopped eating. Check the water first, then match the symptom.
Read the guide →Why Are My Medaka Disappearing?
Fish vanishing one at a time, no bodies, no warning. The four usual suspects, and the dawn oxygen test that finds the most common one.
Read the guide →Why Did My Tub Turn Green?
Green water is an algae bloom, and your fish are fine. Why it happens, why fry keepers cause it on purpose, and the fix that lasts.
Read the guide →Plants and cleanup crew
The floating plants that come free with every fish or snail order, and the snails that work the bottom.
Can Floating Plants Kill Fish?
Too much surface cover can crash the oxygen in a warm tub overnight. What actually causes it, how much of the surface to leave open, and why floaters do not oxygenate water.
Read the guide →Floating Plant Care
Frogbit, salvinia, duckweed, and more. What floaters actually do for a tank, which one to pick, and how to stop them melting. No CO2 or special lighting needed.
Read the guide →Freshwater Snail Care
Japanese Trapdoor and Blueberry Snails. Why livebearers do not overrun a tank, which ones survive winter outdoors, and what a cleanup crew actually does.
Read the guide →Male vs Female Trapdoor Snails
One glance at the tentacles tells you. The curled-tentacle trick for sexing Japanese Trapdoor Snails, plus why a lone female can still surprise you with babies.
Read the guide →Trapdoor vs Mystery vs Nerite Snails
Egg sacks, white shell spots, bulldozed plants, and winter die-offs. Why the Japanese Trapdoor Snail quietly beats the two snails everyone recommends.
Read the guide →Every fish I ship is hand-picked and health-checked in North Carolina, and every order with live fish or snails ships with free floating plants and my live arrival guarantee.
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