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Small Freshwater Fishes for Your Aquarium

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Looking for a small addition to a freshwater aquarium, new or old? For your tank, we have the best small aquarium fish species. All of these fish grow to be less than 3 inches long, but keep in mind that many of these species thrive in small schools of 3 to 5 individuals.

Before adding new fish species, conduct extensive research to ensure that the new fish species’ required environmental parameters match the existing conditions in your aquarium and that all the fish are compatible. To prevent disease transmission, all new fish should be quarantined in a separate tank with separate equipment for 4 to 6 weeks.

Platy Mickey Mouse

Platys are vibrant, live-bearing fish that are ideal for beginners. Because they are live-bearing fish, many hobbyists begin with only a few fish, which can quickly multiply into a large number of fish. The Mickey Mouse Platy is named after a distinct color pattern that forms in the tail peduncle.

Other Platy species include the Red Wagtail, Wagtail, and numerous others.


Guppies are an important part of the small fish aquarium hobby. Guppy tanks, another live-bearing species, are frequently overrun with offspring from frequent breeding. To keep populations from exploding, the best skill any guppy owner can learn is to tell the difference between males and females. Males are smaller and more colorful, while females can have a colorful tail fin but a plain body with a large white belly.

Danio rerio (Zebrafish)

These small, striped fish are one of the few in the aquarium hobby that do not need to be kept in warm tropical temperatures. Zebrafish are peaceful, social creatures who enjoy schooling in groups of 5 or more fish. Danio species in a variety of colors and markings are available in the pet market. There is a long fin variety of zebra danio available, as well as glow colors created by inserting fluorescent genes into the fish.

Tetra Neon

The Neon Tetra is a popular small freshwater aquarium species. These fish are known for their eye-catching appearance, which includes bright red and blue stripes. They make excellent community fish, schooling together in a vibrant wave.

Another species that is very similar is the Cardinal Tetra. Their longer red belly bar that extends all the way to the head distinguishes them from the more common Neon Tetra. A similar species is the Black Neon Tetra, which has black and gold bars instead of red and blue.

Minnow of White Cloud Mountain

Another species of small community fish that does not require warm tropical temperatures is the White Cloud Mountain Minnow. If they are not snack size, these fish do well in temperate tanks with Zebrafish and goldfish. These fish are commonly used in aquascape setups where the emphasis is on the plants rather than the fish, and only a school of one species of fish is added to the aquarium.

Rasbora in Harlequin

The Harlequin Rasbora is a small, schooling fish with a vibrant ruby coloration that contrasts with a black marking on the back half of its body, giving it the ‘harlequin’ appearance. These peaceful fish add a splash of color to aquascaped or planted tanks. Many Rasbora species remain small and do well in community aquariums.