Common and Uncommon Nano Fish for Your Small (or big!) Aquarium

Common and Uncommon Nano Fish for Your Small (or big!) Aquarium

Nano aquariums, typically 5 to 10 gallons, offer the opportunity to witness all the action of a full aquarium ecosystem in a small space - so long as you have equally small inhabitants to go along with it! In this article we’ll cover some nano fish staples as well as some more rare specialty species to inspire your stocking plans. Smaller doesn’t mean less interesting!

Common Nano Species: Reliable and Vibrant

Common nano species offer the benefits of being easier to source, easier on the wallet, and are generally more adapted to aquarium life, making them great choices for keepers of all experience levels. The popular choice is often popular for good reason!

Betta Fish (Betta splendens)

While long finned betta fish are stunningly beautiful, note that the shorter finned plakat species are sometimes healthier and more active without the weight of those long fins. 

The betta fish, also known as the siamese fighting fish, is a nano tank staple - it’s hard to beat their beautiful finnage. Adapted to large but shallow pools in warmer Southeast Asian lowlands, bettas possess a specialized labyrinth organ allowing them to breathe atmospheric air from the surface. They are highly intelligent and can be trained to follow a finger or recognize their owners. Just because they are hardy doesn’t mean they don’t deserve proper care - these fish do best in 5 gallon tanks or larger with proper heating and filtration to mimic the warm, clean waters they see in the wild. They appreciate densely planted tanks, famously using broader leaves such as Anubias as hammocks to sleep in. Choose betta tank mates carefully, as some bettas are highly territorial, but simultaneously slow and susceptible to fin nipping.

Celestial Pearl Danios (Danio margaritatus)

Male celestial pearl danios compete for ladies by “sparring”, where they circle each other and waggle their bright red fins.

Celestial pearl danios, also known as galaxy rasboras, are a beautiful schooling species from clear waters in Myanmar. They feature a deep navy body with cream-colored spots and striking orange-red fins. They rarely exceed one inch in length, making them perfect for 5 gallon tanks. They can be shy species, often darting in and out of densely planted areas. While they are peaceful, males will occasionally engage in "sparring" matches where they circle one another with flared fins to establish dominance. Note that they prefer cooler temperatures than most other aquarium species - try to keep your temperatures lower than 76°F or 24°C.

Honey Gouramis (Trichogaster chuna)

Honey gouramis come in a variety of colours, usually ranging within warm and sunny tones.

Honey gouramis are a peaceful gourami native to clear waters in India and Bangladesh. They reach about two inches and exhibit a beautiful sunset-yellow or deep orange coloration. Like bettas, they are labyrinth fish and will frequently visit the surface. They use their modified pelvic fins as "feelers" to explore their environment. They do best alone or in small groups, and appreciate a densely planted aquarium. Unfortunately, many “honey gouramis” for sale are actually mislabeled thick-lipped gouramis, a much larger and more aggressive species. Take care to ensure you’re buying the right fish, especially when shopping at big box stores.

The lookalike thick lipped gourami can be identified by its more robust face structure and often white/transparent tail fin beginning at the base. This fish can get 4” long and be quite territorial.

Chili Rasboras (Boraras brigittae)

Chili rasboras sometimes seem dull in colour when in the aquarium store, but rest assured they develop a vibrant chilli red colour when comfortable in your tank.

As one of the smallest fish in the hobby, the chili rasbora is perfect for 5-gallon setups. They stay under 0.8 inches and develop an intense, fiery red colour as they mature. Chillis, like other members of the Boraras genus, originate from backwater swamps of Southeast Asia where the water is acidic and tea-stained from the tannins leached from leaves and driftwood. As such, Boraras prefers soft water, and will thrive on our local soft Vancouver tap water. Chilis like friends, and should be kept in groups of 6 or more to feel comfortable.

Ember Tetras (Hyphessobrycon amandae)

Ember tetras are tight, directional schoolers, often moving in unison across the middle of a tank.

Ember Tetras are a highly active tetra whose vibrant colour lives up to their name. They originate from acidic lowland tributaries of Amazonian Brazil, but are hardy and can adjust to most water parameters. Embers grow to about one inch in length, and unlike some larger tetras that can be "nippy," embers are exceptionally peaceful. They are not picky eaters and will readily accept high-quality small pellets and most small frozen foods. These fish are highly prized by aquascapers for the splash of colour they offer against green plants, and sense of scale they provide thanks to their small size.

Endler Guppies (Poecilia wingei)

Endler guppies are just as prolific as their standard cousins!

Endler guppies, native to Venezuela’s Paria Peninsula, are the smaller, more energetic relatives of the common guppy. Pure-strain endlers are prized for their neon-metallic greens, oranges, and blacks. They are very active and spend their day picking at biofilm and algae on plants. They are prolific breeders; in smaller tanks, it is often wise to keep only males to avoid overpopulation. They prefer slightly harder water with a higher pH and are very forgiving of minor fluctuations in water parameters.

Pygmy Corydoras (Corydoras pygmaeus)

Pygmy corydoras remind this author of a flock of small songbirds, always active and gently flitting about!

While most catfish stay strictly on the bottom, pygmy corydoras are unique for their mid-water swimming habits. Originating from the Amazon’s softer waters, they are social, peaceful, and much smaller than other corydoras, reaching only about an inch in length. They have a charming "blinking" behavior and often rest together on broad leaves. Because they have delicate barbels (whiskers) used for foraging, they require a sandy substrate to allow for this natural behaviour. They should be kept in groups of six or more to prevent stress.

Clown Killifish (Epiplatys annulatus)

The clown killifish is also known as the “rocket” killifish due to both its vibrant tail and jumping abilities!

The surface dwelling clown killi is native to slower-moving waters in West Africa and are easily identified by their vertical black-and-cream bands and the brilliant blue reflective "glow" in their eyes. The males also develop a colorful, spade-shaped tail. They are predatory toward tiny insects in nature, so they appreciate small frozen foods like baby brine shrimp. A tight-fitting lid is mandatory, as they are capable of jumping through very small gaps. They thrive in 5-gallon tanks with plenty of floating vegetation.

Uncommon Nano Species: For the Specialist

These species often require specific water parameters, specialized diets, or dedicated "species-only" setups to truly flourish. Consider these species if you’re looking to try something different or more challenging!

Bumblebee Gobies (Brachygobius xanthomelas)

Not all species of “bumblebee goby” can live indefinitely in fresh water. B. xanthomelas is a safe choice for freshwater systems.

Bumblebee gobies are the pugs of the fish world with their small size and stubby features. Native to lowland swamps of Borneo, Java, and Sumatra, these fish are bottom-dwellers with fused pelvic fins that act as suction cups, allowing them to "stick" to rocks or glass. They can be very stubborn eaters, often refusing anything but live or frozen bloodworms and brine shrimp. They are territorial with their own kind, so provide plenty of plants, small caves, or PVC pipes to break lines of sight.

Toothpick Fish (Indostomus sp.)

It’s not hard to see how these fish got their name!

One of the most unusual fish in the hobby, the toothpick fish looks like a pipefish crossed with a gar, shrunken down to the size of half a toothpick. Native to stagnant waters of Myanmar, Thailand, and Malaysia, these fish are exceptionally slender and move with a slow, deliberate "hovering" motion. They are almost invisible in a tank with their preferred decor of driftwood and leaf litter. Much like pipefish, these fish are very delicate eaters, requiring frequent live food feedings and minimal to no competition from other species.

Pygmy Sunfish (Elassoma sp.)

The courtship dance of the pygmy sunfish is one of the most striking displays in the fish world.

Native to the Southeastern United States, these temperate fish are extremely hardy, tolerating most water hardnesses and varying temperatures. Males are stunning, using their velvet black and shimmering blue colours in a spectacular waggle dance to impress females. They do not accept dry foods, and must be fed live cultures. A heavily planted 5-gallon tank will provide the shelter and habitat for them to hunt in. When well fed, they easily breed - a desirable trait as they have shorter lifespans than most aquarium fish.

Licorice Gouramis (Parosphromenus species)

Keeping and breeding licorice gouramis can be a rewarding and meaningful challenge for experienced keepers.

Licorice gouramis are a group of beautiful, small, labyrinth fish from blackwater habitats in Southeast Asia. These fish are highly endangered in the wild, threatened by pollution and habitat loss, and are almost exclusively wild caught. As such, those interested in keeping this fish should do so responsibly, with the aim of breeding and increasing their captive population. These fish generally require extremely soft, acidic, tannin-stained water, with a pH less than 5, TDS as low as possible, and little to no detectable nitrates. In the right environment, males perform spectacular displays with iridescent fins, and will spawn in caves where males defend the eggs. Those interested in learning more about these species may appreciate the resources provided by the Parosphromenus Project.

Least Killifish (Heterandria formosa)

This tiny livebearer is a great option if you’re looking to maintain a breeding population in a small tank.

The least killifish is not at all a killifish, rather, it is the smallest livebearer in the world! Native to Southeastern North America, these tiny 0.8 inch fish are just as prolific as other livebearing species. They are incredibly hardy and can live in a wide range of temperatures. Their coloration is subtle, an olive body with a dark horizontal stripe and a "beauty mark" spot on the dorsal fin. They are fascinating because of a process called "superfetation," where the female carries multiple broods of young at different stages of development, giving birth to one or two fry every few days.

Scarlet Badis (Dario dario)

The scarlet badis’s large personality does not match its small size!

The scarlet badis is a spunky micro-predator from India, with a very similar temperament to small cichlids. Males are brilliant red with silvery-blue vertical bars, while females are smaller and plain grey. They rarely exceed 0.75 inches. They are territorial and will "claim" a small patch of plants or a specific rock. They can be picky eaters and usually require live or frozen foods. Because they are slow and deliberate hunters, they should be kept with peaceful species that won’t outcompete them.

Considerations for Success

While small tanks can be convenient, the smaller water volume presents additional difficulty in keeping fish. Less water means less beneficial bacteria to process waste, and greater instability in water chemistry. To ensure success:

1. Avoid overfeeding: as they say, what goes in one end comes out the other. Feeding an appropriate amount of a high quality food will ensure your fish get what they need without producing unnecessary waste. At April’s we stock a wide variety of high quality diets tailored to the needs of different species. Check out our food section!

2. Ensure adequate filtration: more flow through more filter media yields more waste processing. At April’s we offer a collection of filtration solutions for nano tanks, including slim hang-on-backs and quality sponge filters. Check out our filtration section!

3. Plant densely: Most small fish species suitable for nano aquariums prefer heavily planted tanks, which not only offer cover but help maintain water quality. At April’s, we stock the full line of Tropica plants as well as plants available from other growers. Check out our plant section!

At April’s, we are passionate about nano tanks and the incredible species we can keep in these small ecosystems. We try to keep as many species available to our customers as possible, with new species and varieties coming in all the time. Click here to browse our current species!

Have questions about your next nano tank build? Get in touch via phone, email, or drop in in person - nano tanks are our specialty, we’re always happy to help!