Product Details

Rosy Bitterling – Rhodeus ocellatus

The Rosy Bitterling is a small, attractive temperate freshwater fish known for its peaceful nature, subtle silver body colour and beautiful rosy breeding tones. Also sold as the Rose Bitterling, Japanese Rosy Bitterling, Nippon Bara-tanago or Tairiku Bara-tanago, this species is best suited to cooler planted aquariums, temperate community tanks and seasonal indoor setups. It is a sociable shoaling fish with fascinating breeding behaviour, but it should not be treated as a warm tropical aquarium species.

Key Identification:

Common Name: Rosy Bitterling
Other Names: Rose Bitterling, Japanese Rosy Bitterling, Nippon Bara-tanago, Tairiku Bara-tanago
Scientific Name: Rhodeus ocellatus
Fish Type: Bitterling / Temperate Cyprinid
Water Type: Freshwater

Natural Range & Habitat:

Rhodeus ocellatus is native to Eastern Asia and Taiwan, with introduced populations recorded elsewhere. In the wild, it occurs in shallow ponds, marshes, lowland waters and adjacent irrigation canals, often where aquatic plants, soft margins and calmer water provide shelter.

This species is closely associated with freshwater mussels during breeding. Females use an extended ovipositor to place eggs inside live mussels, where the eggs are fertilised and the young remain protected until they are developed enough to swim freely. In aquariums, this behaviour is unlikely unless suitable live mussels are present and legally sourced, so most keepers maintain them as display fish rather than breeding projects.

Appearance & Adult Size:

Rosy Bitterlings have a small, laterally compressed body with a neat, streamlined shape. Outside breeding condition, they are usually silver, pale gold or lightly translucent, often with a subtle lateral sheen and delicate fin colour.

Mature males can become much more colourful during the breeding season, showing rosy, pink, orange or red tones along the body and fins. Females are usually plainer and may develop a visible ovipositor when ready to spawn. Adults commonly reach around 5–6 cm, though larger specimens may approach 8–9 cm in excellent conditions.

Aquarium Suitability:

This species is best suited to mature temperate aquariums, planted cool-water community tanks and peaceful seasonal displays. It does well in aquariums with open swimming space, planted margins, gentle to moderate flow and clean, well-oxygenated water.

Rosy Bitterlings are not ideal for high-temperature tropical aquariums. They benefit from cooler conditions and, where possible, a seasonal temperature variation rather than constant warmth all year. They are peaceful, but they should be kept with fish that enjoy similar cooler water.

Recommended Aquarium Size:

A practical minimum is 90 litres for a group, with a tank length of at least 75–90 cm recommended. Larger aquariums are better for bigger groups and mixed temperate communities.

Keep in a group of at least 6, with 8 or more preferred where space allows. A proper group improves confidence, reduces stress and encourages natural shoaling behaviour.

Water Conditions:

Temperature: 16–24°C
pH: 7.0–8.0
Hardness: Moderately hard to hard
Additional Notes: Rosy Bitterlings prefer clean, stable, well-oxygenated water and should not be kept long term at high tropical temperatures. A cooler winter period can be beneficial. Avoid soft acidic extremes, poor water quality, stagnant conditions and unstable new aquariums.

Temperament & Tank Mates:

Aquarium Category: Community Fish

Rosy Bitterlings are peaceful shoaling fish suitable for cooler community aquariums. Suitable tank mates include White Cloud Mountain Minnows, Japanese Ricefish, small danios, temperate hillstream loaches, peaceful weather-suitable gobies and other calm fish that enjoy similar cooler, well-oxygenated conditions.

Avoid large predators, aggressive cichlids, fin-nipping species, warm-water tropical fish, delicate slow feeders and any fish that may be stressed by cooler conditions. Do not mix with goldfish in small aquariums, as goldfish can be too messy, too large and too competitive for long-term compatibility.

Feeding:

Rosy Bitterlings are omnivores that feed on small invertebrates, insect larvae, zooplankton, algae and plant-based material. In the aquarium, offer quality flakes, small granules and fine pellets as the staple diet.

Supplement with frozen or live foods such as daphnia, cyclops, mosquito larvae, brineshrimp and small bloodworm. Vegetable or algae-based foods are also useful, especially in a mixed temperate community. Feed small amounts that are eaten quickly to maintain water quality.

Behaviour in the Aquarium:

This is an active but peaceful midwater fish that spends much of its time swimming in loose groups among plants and open water. In a settled aquarium, males may become more colourful and display to females or rival males, especially as temperatures rise after a cooler period.

Breeding behaviour is highly specialised and depends on live freshwater mussels. Females may develop an ovipositor and attempt to spawn if suitable mussels are present. Without mussels, they can still be kept successfully as attractive shoaling fish, but natural reproduction is unlikely.

Care Notes:

Rosy Bitterlings should be kept in a mature aquarium with stable, clean water and a proper group. Avoid consistently high tropical temperatures, poor oxygenation and aggressive tank mates.

Do not release unwanted fish into ponds, waterways or outdoor systems, as bitterlings have been introduced outside their native range in some areas. If attempting breeding, research mussel care carefully and only use legally sourced, appropriate freshwater mussels, as many native mussel species are protected or unsuitable for aquarium use.

Recommended For:

Beginner to intermediate

Availability:

Occasional / Seasonal temperate fish, usually captive-bred or commercially farmed when available

Image Disclaimer:

All images are a visual representation of the fish you will receive, made to be as accurate as possible. Natural variation in size, colour, pattern, body tone and markings can occur between individual fish.