Ricefish Care Guide: Medaka & Daisy's Blue (Oryzias) Tank Size, Diet, Breeding & Tank Mates

Ricefish are one of the most underrated fish in the freshwater hobby — small, peaceful, surprisingly hardy, and gentle enough to live alongside shrimp and snails without picking them apart. They've been kept in Japan for over 500 years (the Medaka is one of the oldest domesticated ornamental fish on Earth), and in the last few years the broader Oryzias family — including the striking electric-blue Daisy's Blue Ricefish from Sulawesi — has finally been catching on with Western aquarists.

This guide covers everything you need to keep both the classic Japanese Medaka and the tropical Daisy's Blue thriving, plus a short section on the outdoor pot-keeping tradition that's quietly building a following in the U.S.

Two Species, Two Setups

The "ricefish" you'll see for sale almost always falls into one of two species:

Medaka (Oryzias latipes) — Native to Japan, Korea, and northern China. Temperate, not tropical. Comes in dozens of color strains: Orange (the most common), Platinum, Miyuki (with an iridescent gold stripe along the spine), Black Diamond, and Youkihi. Tolerates a wide temperature range, from the high 50s°F up through the high 70s, which makes them one of the few aquarium fish that thrive at room temperature with no heater.

Daisy's Blue Ricefish (Oryzias woworae) — Native to Sulawesi, Indonesia. Tropical, smaller, and more colorful: males show a vivid electric blue body with bright red-orange fins, females are paler. Need warmer water (74–82°F) and softer water than Medaka. Slightly more demanding but the payoff is one of the most striking nano fish in the hobby.

If you're keeping ricefish with shrimp in a planted nano, Daisy's Blue is the more popular pick. If you want a cool-water tank or an outdoor pot, go Medaka.

Quick Facts

• Scientific names: Oryzias latipes (Medaka), Oryzias woworae (Daisy's Blue)
• Common names: Medaka, Japanese Ricefish, Daisy's Blue Ricefish, Sulawesi Ricefish
• Origin: East Asia (Medaka) / Sulawesi, Indonesia (Daisy's Blue)
• Adult size: 1.0–1.5 inches
• Lifespan: 2–5 years with good care (longer in cooler conditions)
• Temperament: Peaceful, social, shoaling
• Care level: Beginner

Tank Size and Setup

Ricefish are small but active surface-and-mid-water swimmers, so they appreciate horizontal swimming space more than depth.

Minimum tank size: 10 gallons for a group of 6–8 fish. A 15 or 20-gallon long is even better and lets you keep a proper colony of 10–15. Daisy's Blue can live happily in tanks as small as 5 gallons (with 4–5 fish), but a 10-gallon gives much more stable water parameters and better breeding success.

Filtration: A sponge filter is ideal — gentle current, shrimp-safe, and great biological capacity. Hang-on-back filters work too if you baffle the outflow with a pre-filter sponge so fry and shrimp don't get sucked in.

Substrate: Either fine sand or a dark planted-tank substrate. Dark substrate dramatically improves color contrast on both species — Medaka colors pop, Daisy's Blue fins look almost neon.

Aquascape: Heavy planting along the back and sides with an open swimming area in the front center. Floating plants (frogbit, red root floaters, salvinia, water hyacinth) are particularly important — ricefish are surface-oriented and use floating roots both for cover and as a spawning site.

Lighting: Moderate. Both species show their best color under medium light over a planted aquarium with aquatic plants.

Water Parameters

Medaka (Oryzias latipes)

• Temperature: 60–78°F (15–26°C). No heater required in most homes.
• pH: 7.0–8.0
• GH: 6–15 dGH
• KH: 4–10 dKH

Daisy's Blue (Oryzias woworae)

• Temperature: 74–82°F (23–28°C). Heater recommended.
• pH: 7.0–8.0 (slightly alkaline preferred — counterintuitive for a tropical Asian fish but Sulawesi water is mineral-rich)
• GH: 5–12 dGH
• KH: 3–8 dKH

The most common mistake with Daisy's Blue is keeping them in soft, acidic water assuming they want "tropical Asian" conditions — they actually come from hard alkaline lakes. Standard treated tap water in most of the U.S. works perfectly for both species, especially when combined with regular water changes and a good filtration system to keep the water clean.

Diet and Feeding

Ricefish are unfussy omnivores with small mouths — feed accordingly.

• Staple: Quality micro-pellet or crushed flake food sized for nano fish. Hikari Micro Pellets and Bug Bites Nano work well.
• Supplements: Live or frozen daphnia, baby brine shrimp, cyclops, micro worms, and chopped bloodworms.
• Frequency: 1–2 small feedings per day. Skip a day each week.

Daisy's Blue in particular respond strongly to live food and color noticeably brighter on a varied diet that includes daphnia, baby brine shrimp, and mosquito larvae.

Behavior and Tank Mates

Both species are peaceful, shoaling fish that should be kept in groups of at least 6 (8–10 is better). They're not strictly schooling — they'll loosely associate rather than tightly school — but they need conspecifics to feel secure and display natural behaviors.

Good tank mates:

• Neocaridina shrimp (cherry, blue dream, yellow) — ricefish are too small to eat adult shrimp and generally ignore even shrimplets.
• Pygmy corydoras, habrosus corydoras, hastatus corydoras.
• Small rasboras (chili, phoenix, harlequin).
• Otocinclus.
• Nerite snails and mystery snails.

Tank mates to avoid:

• Anything fin-nipping (tiger barbs, serpae tetras).
• Anything large enough to swallow them (angelfish, gouramis, larger cichlids).
• Bettas — male bettas often pick on ricefish; not recommended.

For shrimp keepers, ricefish are among the safest small aquarium fish you can add to a colony, alongside chili rasboras and pygmy corydoras.

Breeding Ricefish

Ricefish are some of the easiest egg-layers in the hobby and have a behavior you won't see in any other common aquarium fish: females carry their fertilized adhesive eggs attached to their vent (sometimes for hours, sometimes a day or two) before depositing them onto aquatic plants, spawning mops, or floating-plant roots.

To breed:

1. Keep a small colony (4–6 females per 2–3 males) in stable water parameters.
2. Provide spawning mops, fine-leaved plants like java moss, or floating plant roots.
3. Feed live or frozen foods daily to trigger spawning.
4. Once you see clutches of fish eggs attached to plants or mops, transfer them to a separate hatching container or risk the parents eating fry.
5. Eggs hatch in 7–21 days depending on temperature (faster at 78°F, slower at 68°F) — this incubation period varies but is easily managed.
6. Feed hatched fry infusoria, vinegar eels, or powdered fry food for the first week, then baby brine shrimp or baby shrimp.

Breeding success is one of the most rewarding parts of keeping ricefish — colonies often self-sustain for years in a well-planted tank where some fry survive in the floating plants.

Outdoor Pot Keeping (Medaka Only)

In Japan, Medaka are traditionally kept outdoors in shallow ceramic pots, bowls, and small ponds during the warm months — a hobby practice that's now finding fans in the U.S. South, Pacific Northwest, and Mountain West. A 10–30 gallon outdoor container, partially shaded, planted with hornwort and floating plants, and stocked with 6–10 Medaka makes a stunning low-maintenance summer display. Mosquito larvae become a natural food source, colors deepen in natural sunlight, and Medaka breed prolifically.

Important: only Medaka tolerate this — Daisy's Blue are tropical and need a heater. If you're in a climate where pot water drops below the mid-50s°F, bring them indoors before fall.

Common Issues

Most ricefish problems trace back to one of three causes:

Too few fish. A single ricefish or a pair is stressed and rarely shows full color or natural behavior. Always keep 6 or more.

Wrong temperature for the species. Medaka kept at 80°F live shorter lives and breed poorly; Daisy's Blue kept at 68°F slowly decline. Match the fish to your room temperature or invest in a heater.

Strong filter current. Ricefish struggle in heavy flow. If your fish are spending all their time wedged behind plants or in corners, your filter is too strong — switch to a sponge filter or add a pre-filter sponge to reduce intake suction.

Are rice fish easy to care for?

Yes, ricefish are considered easy to care for due to their hardy nature, peaceful temperament, and adaptability to a range of water parameters when proper aquarium setup and feeding are provided.

How cold can rice fish survive?

Medaka ricefish can survive in temperatures as low as the high 50s°F and are suitable for room temperature tanks without a heater. However, Daisy's Blue ricefish are tropical and need water temperatures above 74°F to thrive.

FAQ

Are ricefish good for shrimp tanks? Yes — one of the safest small fish you can add to a shrimp colony. They occasionally eat newborn shrimplets if they find them, but adult shrimp and most juvenile shrimp are ignored.

Do ricefish need a heater? Medaka usually don't (room temperature is fine). Daisy's Blue do.

Can I mix Medaka and Daisy's Blue? Technically yes, but their temperature preferences barely overlap and they don't hybridize. Most keepers pick one species per tank.

How many ricefish should I keep? Minimum 6, ideally 8–10. They're shoaling fish and behave very differently in proper-sized groups.

Why are my ricefish hiding? Almost always either too few fish in the group, too much current, or not enough cover. Add fish, slow the filter, add floating plants.

Ricefish and Aquarium Supplies at Tropical Treasures Wyo

We stock both Medaka color strains and Daisy's Blue Ricefish (seasonally), along with sponge filters, nano-fish food, floating plants, and shrimp-safe substrate to set up the perfect ricefish tank. Shop Live Fish or visit us at 190 S College Drive, Suite D, Cheyenne, WY 82007. We ship live fish nationwide with guaranteed live arrival.

Related guides: Neocaridina Shrimp Care · Best Fish for 10 Gallon Tanks · Best Low-Light Plants · Nitrogen Cycle Guide · Aquarium Filtration Guide · How to Set Up Your First Aquarium