Medaka (Japanese rice fish) with shrimp
The medaka, or Japanese rice fish (Oryzias latipes), is a small, peaceful schooling fish from shallow, slow and heavily vegetated waters such as rice paddies, ponds and marshes in Japan and nearby parts of Asia (The Shrimp Farm, Aquarium Co-Op). It has been kept as a pet in Japan for centuries and now comes in many line-bred colors, from orange "Youkihi" to black, white and blue-shimmering forms (The Shrimp Farm). Its big selling point for shrimp keepers is temperature: it likes the same cool, room-temperature water as cherry shrimp.
Medaka at a glance
| Medaka (Oryzias latipes) | |
|---|---|
| Adult size | Up to about 1.5 in (4 cm) (The Shrimp Farm, Aquarium Co-Op); 36 mm standard length (Seriously Fish) |
| Wild home | Shallow, slow, heavily vegetated water: rice paddies, ponds, marshes and slow rivers; can live in fresh and brackish water (The Shrimp Farm, Aquarium Co-Op) |
| Temperature | 64.5–71.5 °F considered ideal, though they tolerate a very wide range (The Shrimp Farm); 60–75 °F (Aquarium Co-Op); 61–72 °F (Seriously Fish) |
| pH | 6.5–8.5 (Aquarium Co-Op, Seriously Fish); around neutral works well (The Shrimp Farm) |
| Hardness | Moderately soft to very hard (Aquarium Co-Op); 5–25 dGH (Seriously Fish) |
| Tank | 10 gallons (long) for 5–6 fish (The Shrimp Farm); 10 gallons with a sponge filter (Aquarium Co-Op); 18 × 12 in base for a group (Seriously Fish) |
| Group | 6 or more (Aquarium Co-Op); most confident in a group of 8 or more (Seriously Fish) |
| Lifespan | About 3 years on average, up to 5 (The Shrimp Farm); up to 5 years in captivity (Aquarium Co-Op) |
| Temperament | Peaceful (all three); males may chase each other (Aquarium Co-Op) |
Will medaka eat shrimp?
- Adults: no. The Shrimp Farm's tankmates list rates medaka as "does not eat adult shrimp", and Aquarium Co-Op says they can live with adult Neocaridina cherry shrimp.
- Shrimplets: yes, when they can. The Shrimp Farm says medaka will eat baby shrimp if they can and should not go in with your most expensive colonies. Medaka are surface-oriented micropredators that hunt small insects and larvae in the wild (The Shrimp Farm). Our inference: a shrimplet out in open water is at risk, while babies hiding in moss on the bottom are much safer.
- Which shrimp: The Shrimp Farm says that in a nicely planted tank, Neocaridina and some Caridina dwarf shrimp thrive alongside them. Aquarium Co-Op also lists Amano shrimp and snails as good medaka tank mates. See Amano shrimp care.
Our reading: medaka are one of the better fish for a room-temperature cherry shrimp tank, as long as you are happy with a slower-growing colony. For other cool-water options, compare white cloud minnows with shrimp (which The Shrimp Farm also lists as a medaka tank mate), and see the full list in cherry shrimp tank mates.
The flip side: shrimp eat medaka eggs
Aquarium Co-Op says adult shrimp may eat rice fish eggs. Female medaka carry a ball of sticky eggs at the anal fin for a while, then deposit them on fine-leaved plants, spawning mops or even sponge filters (The Shrimp Farm, Aquarium Co-Op). If you want baby medaka as well as baby shrimp, move the eggs or the spawning mop to a separate container; The Shrimp Farm says the eggs hatch in 1 to 3 weeks depending on temperature, and Aquarium Co-Op says a little under a week at 77 °F. Seriously Fish adds that adults mostly ignore the eggs but do eat free-swimming fry, and that dense planting lets some fry survive.
Matching the water
| Parameter | Medaka (The Shrimp Farm / Aquarium Co-Op / Seriously Fish) | Cherry type Neocaridina (The Shrimp Farm) | Shared zone |
|---|---|---|---|
| Temperature | 64.5–71.5 °F / 60–75 °F / 61–72 °F | 65–85 °F | About 65–72 °F |
| pH | Around neutral / 6.5–8.5 / 6.5–8.5 | 6.2–8.0 | About 6.5–8.0 |
| GH | Moderately soft to very hard / 5–25 dGH | 4–8 | About 5–8 |
The shared zone is our comparison of the published ranges, not a tested target. The overlap sits at the cool end of the cherry shrimp range, which is the point of this pairing: The Shrimp Farm says a heater isn't necessary if your home stays at room temperature, and warns that keeping medaka warm enough for typical tropical fish shortens their lifespan. That also means medaka don't suit a warm tank with tropical fish. See shrimp tank temperature, do you need a heater and shrimp GH and KH explained.
Tank size and setup
- Tank: a 10-gallon long tank for a small group of 5–6 (The Shrimp Farm); Seriously Fish suggests an 18 × 12 in base for a group. See how many shrimp per gallon.
- Lid: both The Shrimp Farm and Aquarium Co-Op say medaka jump when startled; use a lid or plenty of floating plants.
- Plants and light: The Shrimp Farm says to go heavy on plants and add floating plants to dim the light, since medaka don't like it too bright. Moss on the bottom gives shrimplets cover (java moss for shrimp).
- Gentle flow: Aquarium Co-Op suggests a sponge filter for slower current, which is also shrimplet-safe (shrimp-safe filters).
- Mature tank: The Shrimp Farm says to add medaka only to a fully cycled aquarium, with weekly temperature-matched water changes. See how to cycle a shrimp tank.
Feeding both
Medaka prefer tiny foods that float at the surface (Aquarium Co-Op). The Shrimp Farm suggests small floating carnivore pellets or flakes as a staple, plus frozen or live foods; Aquarium Co-Op lists crushed flakes, freeze-dried tubifex worms and small fish foods. Because medaka eat at the top and shrimp graze the bottom, the two rarely compete, but well-fed fish are less likely to go hunting. Feed the shrimp separately; see best shrimp food and what do shrimp eat.
Medaka in a pond or tub
Medaka are popular pond fish in Japan (The Shrimp Farm), and Aquarium Co-Op calls them beginner-friendly for an aquarium or an outdoor pond. If you keep shrimp in an outdoor tub with them, the same rules apply: adults are safe, babies need dense cover. Outdoor temperatures swing far more than a room does, so check your local climate before trying it.
How to add medaka to a shrimp tank
- Shrimp first. Practical Fishkeeping suggests letting the colony build up before adding fish.
- Buy a group of one species: Seriously Fish says not to keep medaka with other Oryzias species if you want to breed them, because they can hybridize.
- Quarantine the fish separately. Practical Fishkeeping says many fish medications are not safe for invertebrates. If fish get sick, ask a fish veterinarian or an experienced store about treatment that won't harm the shrimp. See how to quarantine and is copper toxic to shrimp.
Common mistakes
- Adding medaka to a warm tropical tank.
- No lid.
- Keeping only one or two.
- Bright light with no floating cover.
- No moss or plants for shrimplets.
- Expecting medaka fry to survive in a shrimp tank without moving the eggs.
Track it
Log temperature, pH, GH and TDS on the free Water Parameter Log printable so you can keep the tank in the range both species share.
Frequently asked questions
Do medaka eat shrimp?
Not adult shrimp. The Shrimp Farm rates medaka as not eating adult shrimp, but says they will eat baby shrimp if they can.
Can medaka live with cherry shrimp?
Yes, in a planted tank. Aquarium Co-Op says medaka can live with adult Neocaridina cherry shrimp; expect some shrimplet losses and give babies dense moss.
Do shrimp eat medaka eggs?
They may. Aquarium Co-Op says adult shrimp may eat rice fish eggs, so move eggs or spawning mops to a separate container if you want medaka fry.
Do medaka need a heater with shrimp?
Usually not. The Shrimp Farm says a heater isn't necessary if your home stays at room temperature, and lists 64.5 to 71.5 °F as ideal.
How many medaka should I keep?
Six or more, per Aquarium Co-Op; Seriously Fish says they look and behave best in a group of 8 or more.
What size tank do medaka need?
The Shrimp Farm says a 10-gallon long tank for a small group of 5 to 6, with a lid because they jump.
Sources: The Shrimp Farm, Shrimp tankmates and compatibility (Japanese ricefish Oryzias latipes, up to 1.5 in, 10+ gallons, easy, does not eat adult shrimp); The Shrimp Farm, Japanese rice fish (medaka) care (fresh and brackish water; shallow, heavily vegetated waters such as rice paddies; up to about 1.5 in; color varieties; 10-gallon long tank for 5–6 fish; lid, they jump when startled; heavy planting and floating plants, dislike bright light; fully cycled tank, pH around neutral, no heater needed at room temperature, weekly temperature-matched water changes; 64.5–71.5 °F considered ideal; warm tropical tanks shorten lifespan; will eat baby shrimp if they can, not with expensive colonies, Neocaridina and some Caridina thrive alongside them in a planted set-up; micropredators fed small floating carnivore pellets or flakes plus frozen or live foods; females carry an egg ball then deposit it in fine-leaved plants; eggs hatch after 1–3 weeks; about 3 years average, up to 5); Aquarium Co-Op, Care guide for medaka rice fish (up to 1.5 in/4 cm; 60–75 °F, pH 6.5–8.5, moderately soft to very hard GH; 10-gallon tank with sponge filter; may jump, use a lid or floating plants; school of six or more; tank mates include white clouds, hillstream loaches, Amano shrimp and snails; can live with adult Neocaridina cherry shrimp but may eat baby shrimp, and adult shrimp may eat rice fish eggs; tiny floating foods; eggs on plants, mops and sponge filters; hatch in a little under a week at 77 °F; up to 5 years in captivity); Seriously Fish, Oryzias latipes (medaka) (36 mm SL; 18 × 12 in base for a group; heavily planted; 61–72 °F, pH 6.5–8.5, 5–25 dGH; peaceful; not with other Oryzias spp. because of hybridization; group of 8 or more; adults mostly ignore eggs but eat free-swimming fry, dense planting helps fry survive); Practical Fishkeeping, What can I keep with shrimp? (let the colony build first; many fish medications unsafe for invertebrates); The Shrimp Farm, Red rili shrimp tank set-up and care (cherry-type Neocaridina: 65–85 °F, pH 6.2–8.0, GH 4–8). The shared water zone is our own comparison of these ranges.