Nano fish tanks are very popular for their beauty and compact size, but it can be challenging to find animals that are tiny enough to comfortably live in them. If you only have room for a 5- to 20-gallon aquarium, check out our top 10 small aquarium fish that are known for their vibrant colors, fun personalities, and unique appearances.
1. Celestial Pearl Danio
Also known as the galaxy rasbora or CPD, this little fish has been extremely popular ever since its discovery in 2006. Originally from Southeast Asia, it kind of looks like a 1-inch (2.5 cm) miniature trout covered in shiny golden spots and bright orange fins. They can be a little pricier at $6-10 each, so save up your money to get at least six of these schooling fish. CPDs are known to be a bit shy, so make them feel safer by increasing the size of their group and providing plenty of decorations and aquarium plants as cover. Plus, they prefer feeding midwater (not at the top or bottom of the tank), so look for small, slowly sinking foods such as frozen cyclops, baby brine shrimp, and daphnia.
2. Chili Rasbora
Chili rasboras get their common name from the fiery red color they display as full-grown adults, but most of time you see juveniles at the fish store that are much paler in appearance. If you bring them home and take good care of them, your patience will be rewarded when their coloration blossoms six months down the road. As one of the smallest fish on our list, they grow up to 0.8 inch (2 cm) in length with a very slender profile. Because of their petite size, they look better if you get at least 10 brigittae rasboras in a school and put them against a lush green background of plants. As with the celestial pearl danios, feed them tiny foods that swirl midwater in the aquarium, such as baby brine shrimp, crushed flakes, and Easy Fry and Small Fish Food.
3. Pygmy Corydoras
The 1-inch (2.5 cm) pygmy corydoras are incredibly adorable because they always stay the size of baby cory catfish. They pair well with the previous schooling midwater fish because they can use their whisker-like barbels to detect and clean up any crumbs that fall past them to the ground. They enjoy eating just about any fish food, including sinking wafers and Repashy gel food. Pygmy corys are a schooling fish that require at least six or more to feel comfortable, but if you’re having trouble locating them at fish stores, consider the other dwarf corydoras species, like C. habrosus and C. hastatus. For more info on how to care for cory catfish, see our care guide.
4. Kuhli Loach
This bottom dweller is not quite a micro fish since it can reach up to 4 inches (10 cm) in length, but they do not produce much bioload or waste because of their skinny, eel-like bodies. Their unusual appearance and peaceful demeanor make them the perfect oddball creature to keep with your other nano fish. Kuhli loaches are a great beginner fish since they are not picky when it comes to water parameters and food preferences. For additional color variations, check out the black kuhli loach (P. oblonga) and silver kuhli loach (P. anguillaris). You can read all about them in the full care guide here.
5. Green Neon Tetra
As a slightly smaller cousin of the regular neon tetra, Paracheirodon simulans only gets 1-1.25 inches (2.5-3 cm) long and doesn’t have much of a red stripe. Instead, its body is predominantly covered in a bright blue-green, horizontal stripe that shines brilliantly even when the light is dim. They can live in slightly more acidic water, but otherwise thrive in standard water parameters for a tropical community tank. Get a school of at least 6-8 green neon tetras and feed them plenty of small, slowly sinking fish foods. Also, many of them are caught from the wild and may come with fin rot or ich, so make sure to quarantine them after purchase to prevent disease from spreading to your other aquariums.
6. Clown Killifish
Epiplatys annulatus (male is above and female is below)
The banded panchax or rocket killifish is known for its dark vertical bands and dazzling tail that looks the flame coming out of a rocket. The males have all the amazing colors, whereas the females have the banded body with a clear tail. Because the guys can be a bit territorial with each other, aim for a group with a ratio of 1 male for every 2-3 females. This 1.5-inch (3.8 cm), top-dwelling fish prefers to hang out in the upper third of the aquarium, so use a tight-fitting lid with all the holes plugged up so that they won’t jump out. Offer them floating foods such as freeze-dried tubifex worms and flakes, and they should start spawning and scattering their eggs. For more details, read our article on clown killies.
7. Ember Tetra
This 0.8-inch (2 cm) tetra from Brazil boasts a bright orange-red body that lights up any aquarium, especially those with lush, green plants. They are very hardy and would do well in either a nano tank or as a school of 20-30 fish in a larger tank. Unlike many nano fish, ember tetras are relatively outgoing and eagerly eat from all levels of the aquarium. Feed them floating or slowly sinking foods like Xtreme Nano pellets, Hikari Micro Pellets, and frozen daphnia.
8. Panda Guppy
Finally, we have a livebearer (or fish that bears live young) on our list. Guppies are very well-known in the hobby, but they usually grow up to 2.5 inches (6 cm) long. Panda guppies are specifically bred to maintain a small size with a shorter tail, such that males come in around 1 inch (2.5 cm) and females around 1.75-2 inches (4-5 cm). They have striking blue, silver, and black colors and, like most livebearers, breed quite readily.
Compared to other fancy guppies, we don’t find them to be very fussy and have even raised them in an outdoor mini pond during the warmer summer season. They do prefer higher pH and GH with more minerals, so consider adding Wonder Shells or Seachem Equilibrium if you have soft water. Fortunately, they are easy to feed and readily eat at all levels of the aquarium, so you don’t need to get a bottom dweller to clean up your nano tank. Panda guppies are one of our favorite varieties, so make sure to give them a shot. See our full guppy care guide for more details.
9. Spotted Blue Eye Rainbowfish
If you have always loved rainbowfish but don’t have a tank big enough for them, try Pseudomugil rainbowfish like Gertrude’s rainbowfish. This lovely, 1.5-inch (3.5 cm) species has a yellow or light blue body (depending on its native region), black spots, and bright blue eyes. While the males are more colorful than the females, get one male for every two females so that the boys will show off their best colors and unique sparring dance. Like the guppies, they do prefer higher pH and GH, but can live in a very wide temperature range.
As a surface-dwelling fish that likes to swim in the top half of the aquarium, get a tight-fitting lid to prevent jumping and feed lots of floating foods like flakes and freeze-dried foods. While Pseudomugil rainbowfish are very lively and beautiful, they tend to have a shorter lifespan, so consider breeding them by using dense floating plants like guppy grass or spawning mops made out of yarn.
10. Borneo Sucker Loach
Last but not least, we have an algae eater for your nano fish tank. The Gastromyzon genus consists of hillstream loaches that usually stay 2 inches (5 cm) in length and are shaped like miniature stingrays or flounders. Like their larger cousin, the reticulated hillstream loach, they enjoy cleaning off driftwood, scavenging for leftovers, and of course eating algae. They can be kept in normal community tank parameters, but also have the ability to tolerate the cooler temperatures of an unheated aquarium. Borneo sucker loaches can show some territorial behavior toward their own kind, so either get one individual or a group of three or more.
If you are unable to find these fish at your local fish store, check out our favorite online retailers to see about ordering them online. Best of luck with your nano tank and enjoy nature daily.