Rainbow bitterling
Acheilognathus macropterus
Also known as Giant bitterling, Largefin bitterling
FreshwaterFish
Care at a glance
- Temperature
- 57–79°F
- 14–26°C
- pH
- 6.5–7.8
- Adult size
- 10.6 in
- 27 cm
- Minimum tank
- 106 gal
- 400 L
- Temperament
- Mostly peaceful
- Social behavior
- Schooling
- Swim level
- Middle
- Diet
- Omnivore
- Difficulty
- Medium
- Breeding
- Egg layer · Hard
- Rarity
- Rare
- Family
- Acheilognathidae
- Origin
- Amur to Yangtze river systems, East Asia
Overview
The rainbow bitterling is a big, coolwater schooling fish for a large tank or a pond. It is best kept by someone with a little experience.
Did you know
Most bitterlings are palm-sized fish under 10 centimeters, but the rainbow bitterling is the giant of the group. It grows larger than many of the barbs and minnows it is related to.
Caring for the rainbow bitterling
Give rainbow bitterlings pond-scale space, a large tank or pond of at least 106 gal (400 L). Keep six or more, since they shoal by nature and grow calmer and more colorful in a crowd. They swim in the middle water. A planted setup with a soft substrate, gentle flow and room to grow suits them.
The rainbow bitterling handles a broad range of 57 to 79°F (14 to 26°C), with a near-neutral pH of 6.5 to 7.8. It does best cool, with a winter rest.
Feed it as an omnivore, with frozen foods, sinking pellets, flake and vegetable matter. It is generally peaceful, but a fish this large should share space only with other sizable, temperate tank mates.
In the breeding season, males flush violet and rose, and their dorsal fin lengthens. Like all bitterlings, it spawns inside living freshwater mussels, which makes aquarium breeding hard.
Good to know
The rainbow bitterling belongs to the family Acheilognathidae and is also sold as the giant or largefin bitterling. The name macropterus means large-finned, after the male's extended dorsal fin.
In the wild
The rainbow bitterling cruises weedy backwaters and slow rivers across East Asia, from the Amur south to the Yangtze systems.
Symbiotic relationships
Bitterlings and freshwater mussels
Bitterlings do not lay their eggs in the open at all. In spring the female grows a long egg tube and slips her eggs through the outflow siphon of a living freshwater mussel, into its gill chamber, while the male releases sperm over the inflow siphon so the mussel draws it in. The embryos develop inside the mussel for about a month, protected from everything, then swim out. The mussel's own larvae attach to passing fish to develop, so the two use each other. Biologists now read it as a mild parasitism running both ways rather than a partnership: the eggs cost the mussel oxygen and food, and bitterlings have evolved to shed the mussel larvae that other fish carry.
Bitterlings are cool-water fish for an unheated tank and breed only with a live mussel present. Swan or duck mussels are the usual hosts; they are filter feeders that starve in clean water and need a mature, well fed tank with fine sand to sit in, which is why breeding bitterlings is a project rather than a happy accident. Watch the female's egg tube lengthen and the male stake out the mussel, and you have seen the whole ritual.
Weekly picks
Tank mates
The rainbow bitterling is a mostly peaceful, schooling species that keeps to the middle. These picks share a community profile with it, are safe together in both directions, and overlap on water type, temperature and pH.
Black-top mouse catfish
Hassar orestis
Freshwater11.8 in (30 cm) · 106 gal (400 L)73–82°F (23–28°C)
Largescale four-eyed fish
Anableps anableps
FreshwaterBrackish11.8 in (30 cm) · 70 gal (265 L)77–88°F (25–31°C)
Fourspot hemiodus
Hemiodus quadrimaculatus
Freshwater6.3 in (16 cm) · 106 gal (400 L)75–82°F (24–28°C)
Wilder's mouse catfish
Hassar wilderi
Freshwater9.8 in (25 cm) · 106 gal (400 L)73–82°F (23–28°C)
Giant river hatchetfish
Triportheus rotundatus
Freshwater9.8 in (25 cm) · 79 gal (300 L)73–82°F (23–28°C)
Redhook
Myloplus rubripinnis
Freshwater9.8 in (25 cm) · 70 gal (265 L)73–81°F (23–27°C)
Common questions
What size tank does a rainbow bitterling need?
A rainbow bitterling needs at least 106 gal (400 L). It spends most of its time in the middle.
What temperature and pH does a rainbow bitterling need?
A rainbow bitterling is comfortable at 57–79°F (14–26°C) with a pH of 6.5–7.8.
What does a rainbow bitterling eat?
A rainbow bitterling is an omnivore. It eats frozen foods, sinking pellets and flake, along with vegetable matter.
How big does a rainbow bitterling get?
An adult rainbow bitterling reaches about 10.6 in (27 cm).
Does a rainbow bitterling need a group?
Yes. A rainbow bitterling is a schooling species and should be kept in a group, not singly.
How can you tell a male rainbow bitterling from a female?
In the breeding season, males flush violet and rose, and their dorsal fin grows longer.
How does a rainbow bitterling breed?
A rainbow bitterling spawns inside a living freshwater mussel, as all bitterlings do. That makes breeding it in an aquarium hard.
Related species
- 4.7 in (12 cm)40 gal (150 L)61–79°F (16–26°C)
Red-tail bitterling
Acheilognathus tonkinensis
4.7 in (12 cm) · 40 gal (150 L)
3.1 in (8 cm)30 gal (112 L)57–79°F (14–26°C)Blue Amur bitterling
Paracheilognathus himantegus
3.1 in (8 cm) · 30 gal (112 L)
3.1 in (8 cm)21 gal (80 L)64–75°F (18–24°C)Rosy bitterling
Rhodeus ocellatus
3.1 in (8 cm) · 21 gal (80 L)
10.6 in (27 cm)201 gal (760 L)68–82°F (20–28°C)Banded leporinus
Leporinus fasciatus
10.6 in (27 cm) · 201 gal (760 L)
11 in (28 cm)159 gal (600 L)73–82°F (23–28°C)Sailfin red hook
Myleus setiger
11 in (28 cm) · 159 gal (600 L)
11 in (28 cm)92 gal (350 L)75–82°F (24–28°C)Tailbar cichlid
Vieja hartwegi
11 in (28 cm) · 92 gal (350 L)