Most ornamental aquarium fish are tropical fish that require warm water to survive, typically 72-82 degrees Fahrenheit (22-28 Celsius). However, there are some species that can survive cooler water than most tropical fish, even down to 50-60 degrees F (10-15 C). Some coldwater ornamental fish may grow so large that they are only suitable for outdoor ponds. Koi can be purchased at fish stores at a few inches long, so you might think they are good cool-water aquarium fish, but they are about three feet long when fully grown!
The most commonly kept cold-water fish species is the goldfish, but even that fish can grow to a foot long, much too big for a small aquarium. And yet there are many other interesting fish species that do not require a heated tank. The temperate zones on all continents have fish that prefer cold water and can be kept in an aquarium.
If you are planning to set up your cold-water aquarium, here are 11 fish that grow to suitable sizes and will be able to flourish in your aquarium.
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Hailing from Afghanistan and Bangladesh, this little fish is tolerant of temperatures in the mid-60s Fahrenheit (18 C), or even lower. They are easy to care for and are suitable for a community aquarium. Undemanding and beautiful, the rosy barb (Pethia conchonius, formerly Barbus conchonius) is also considered one of the hardiest barbs.
Length: Up to 6 inches
Physical Characteristics: Long thin fish with iridescent pinkish sides and large scales; ventral fins that are saturated red at the base; bluish edged anal fin with a hooked outgrowth or barb (on males).
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The gold barb, or Chinese barb, is an extremely popular cold-water fish. Barbs are schooling fish that should be kept in groups of 5-6 fish, or more. Any aquarium containing gold barbs should maintain a moderate current. A dedicated river tank is not necessary, but some flow from a powerhead should be provided. The gold barb (Barbodes semifasciolatus, previously named Puntius semifasciolatus or Barbus schuberti), also comes in a less common green variety.
Length: 2 to 3 inches
Physical Characteristics: Bright, shiny golden yellow body color that was developed through selective breeding. In the wild, they are greenish colored.
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Two Spot Barb
This fish hails from Nepal, India, and Pakistan. The omnivorous two spot barb (Pethia ticto, formerly Barbus ticto) can be a bright red fish. The darkness of its spots and the brightness of the red lateral color match the quality of its varied diet; it is recommended to give them live food, flake food, and some algae. Counter to its name, this barb has no barbels at all.
Length: 3 to 5 inches
Physical Characteristics: Silvery body, one black spot near the head and one near the tail; dorsal fin reddish with black spots (male); no barbels.
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Natives to Southern Brazil and Paraguay, both the standard bloodfin (Aphyocharax anisitsi), and the false bloodfin (Aphyocharax dentatus) tolerate temperatures as low as the mid-60s. Peaceful omnivores, they are easy to care for and are quite hardy. As such, bloodfin tetras are offered in many pet shops. These tetras are active surface dwellers and are best kept in schools.
Length: 2 to 3 inches
Physical Characteristics: Silvery long thin body; all fins colored red; tetras have no barbels, but have an small adipose fin on the caudal peduncle.Continue to 5 of 11 below.
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Buenos Aires Tetra
Buenos Aires tetra (Psalidodon anisitsi, formerly Hemigrammus caudovittatus) are easily found for sale and will tolerate temperatures into the mid-60s F (18 C). Choose between standard and the albino variants. Like the bloodfin tetras, they are undemanding and easy to care for. They are suitable for a community tank but will voraciously eat live plants.
Length: 2 to 3 inches
Physical Characteristics: Silvery fish with a back of olive and brown; anal, ventral, and dorsal fins are yellowish to reddish; red upper part of the iris of the eye; a dark diamond-shaped spot near the tail fin base.
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Originally from Asia, Goldfish (Carassius auratus) are probably the most readily available fish in captivity. There are many attractive variations of this popular and hardy fish. Fancy goldfish have long, double caudal fins (tails) that may be as long as the body. The comet goldfish has a long, single tail and is usually found in the golden coloration, but can also occur in white, orange and white, and black, orange and white coloration.
Length: 8-12 inches
Physical Characteristics: Elongated bodies with a single tail fin in common, comet and shubunkin varieties. Many body shapes with twin tails, such as ryukin, and oranda goldfish.
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These striking bottom-dwelling fish (Gastromyzon punctulatus) are from South and East Asia. Although these fish are not often seen in pet shops, individuals can be found for sale from time to time. Not all of them prefer cool temperatures, but most will tolerate temperatures that fall into the mid to upper 60s F (15-20 C).
Length: Up to 3 inches
Physical Characteristics: black and yellow, spotted along the head and back; long stripes along the sides; flattened top to bottom; wide and round pectoral and pelvic fins that form a ventral sucker.
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Like the zebra danio, the pearl danio (Danio albolineatus) is very hardy and easy to care for. It will tolerate temperatures into the mid-60s without difficulty and is easy to find. Pearl danios are larger than zebra danios, but they need not be kept in schools. They are native to Sumatra, Laos and Thailand.
Length: 2 inches
Physical Characteristics: Forked tail, paired barbels, pearlescent color.Continue to 9 of 11 below.
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Readily available, the weather loach (Misgurnus angullicaudatus) from East Asia is one of the easiest fish to care for. Couple that with the fact that they will tolerate temperatures in the 50s F (10 C), they are excellent candidates for a cold water tank. This fish becomes more active when the barometer drops before a storm, hence the name.
Length: 5 to 8 inches
Physical Characteristics: Pink, albino, or gray body; elongated shape like an eel; 3 sets of barbels surrounding the mouth, appearing like a mop.
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White Cloud Mountain Minnow
Almost extinct in its native China due to pollution, this is one of the easiest fish to care for. The white cloud minnow (Tanichthys albonubes) does best in cooler temperatures. A new gold-colored variant has become very popular, although very low temperatures will dampen their attractive coloration.
Length: 1.5 inches
Physical Characteristics: Silver green, rosy pink, or gold body with red caudal and dorsal fin; brighter colors, slimmer in body, fan-shaped dorsal and anal fins (male); white distended abdomen, wedge-shaped fins (female).
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After the goldfish, the zebra danio (Danio rerio, Brachydanio rerio formerly) is the next most readily available of all the cold-water fish. Native to South Asia, they tolerate temperatures that fall into the mid-60s F (18 C) and are very easy to care for. Long-finned forms are available, as well as a popular leopard-spotted variety.
Length: 1 to 1.5 inches
Physical Characteristics: Five uniform horizontal blue stripes extending to caudal fin; laterally compressed shape, with the mouth directed upward; torpedo-shaped with gold stripes between the blue (male); whitish belly with silver stripes between the blue (female)
Unless you are planning on putting it into a pond, avoid the one cold-water species known as the Chinese High-Fin Banded Shark, also called the Wimple Carp, or the Freshwater Batfish (Myxocyprinus asiaticus), referencing its high triangle-shaped dorsal fin and black banding on young fish. It is often sold at a few inches long in pet stores, but can grow to eight inches in the first year, then this cute little fish (not a shark) ultimately grows to four and a half feet long. Hence it is not appropriate for most aquaria.