What Can Live With Medaka?
Medaka are peaceful, small, and completely unequipped to defend themselves, which makes choosing tank mates simpler than it looks. Two questions settle almost every case: can it fit a medaka in its mouth, and does it want the same water temperature?
The two rules
Rule one: anything that can eat a medaka eventually will. An adult medaka is under two inches and has no defences. Fish that are peaceful toward things their own size are still predators toward something this small.
Rule two: medaka are temperate. They want water most tropical fish find too cool, and they benefit from a seasonal swing. Housing them with a tropical fish means running a heater, which is fine for the tropical fish and not ideal for the medaka.
Most "can these live together" questions answer themselves once you apply both.
| Tank mate | Verdict | Why |
|---|---|---|
| Freshwater snails | Yes, ideal | No conflict at all, and they clean the bottom |
| Shrimp (adults) | Usually yes | Adults are safe; shrimplets may get eaten |
| Other medaka | Yes | They shoal, more is better |
| White Cloud minnows | Often fine | Similar size and temperature needs |
| Betta | No | Wants tropical warmth, and is aggressive toward other fish |
| Goldfish | No | Big enough to eat them, and far messier |
| Koi | No | Big enough to eat them, and will take any eggs or fry |
| Guppies | Compromise | Peaceful, but tropical and they interbreed with nothing here |
"Usually" and "often" mean exactly that. Individual fish vary, and a hungry fish of any species is less predictable than a well fed one.
Snails: the easiest yes
Snails are the tank mate I recommend without reservation. They occupy the bottom, which medaka largely ignore, they graze algae and detritus, and there is no scenario where either animal bothers the other. Japanese Trapdoor Snails are the natural pairing, since they handle the same cold and can overwinter outdoors alongside medaka.
Blueberry Snails work equally well but are not cold-hardy in the same way, so they come indoors before winter. My snail care guide covers the difference.
Shrimp: yes, with one caveat
Adult shrimp and medaka coexist well. The caveat is shrimplets: newly hatched shrimp are small enough to be food, and medaka are opportunistic surface feeders that will not turn one down. In a bare tank a shrimp colony may not grow. In a heavily planted one with moss and cover, enough survive to keep the population going.
So keep both if you want both, but plant heavily if you want the shrimp to actually breed.
The real answer about other fish
My real recommendation is a medaka-only container, plus snails. Not because medaka are difficult, but because the things that make them wonderful, the small size, the no-heater lifestyle, the breeding, all get compromised by adding another fish.
The breeding point deserves emphasis. Any tank mate large enough to be interesting is large enough to eat medaka fry, so a mixed tank quietly means no babies. If part of the appeal is watching a group become a bigger group, keep them on their own.
What about mixing medaka varieties?
Different medaka lines live together perfectly happily, and a mixed group is genuinely beautiful. Just know that they will interbreed, so if you are trying to maintain a specific line you need them separated. If you simply want a colorful tub, mix freely, which is exactly what my Breeder's Choice Collection is, off-label beauties that can include the odd true line fish.
Trapdoor Snails handle the same cold as medaka and overwinter outdoors alongside them, grazing algae the whole time. Add a few to any live order and both ship together.
Shop SnailsCommon questions
Can medaka live with shrimp?
Yes, adult shrimp and medaka coexist well. The caveat is baby shrimp, which are small enough for medaka to eat. In a heavily planted tank with moss and cover, enough shrimplets survive for the colony to grow; in a bare tank it may not.
Can medaka live with a betta?
Not recommended. Bettas need tropical temperatures that medaka do not want, and bettas can be aggressive toward other fish. Medaka are better kept in unheated water on their own.
Can medaka live with goldfish or koi?
No. Both grow large enough to eat adult medaka, and both produce far more waste than a medaka-suitable container can handle. Goldfish and koi need pond-scale water volume, while medaka thrive in tubs and small tanks.
What is the best tank mate for medaka?
Freshwater snails. Japanese Trapdoor Snails are the ideal pairing because they tolerate the same cold and can overwinter outdoors alongside medaka, they graze algae on the bottom, and neither animal bothers the other.