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If you have a small aquarium of under 10 gallons, finding the right fish to stock it with can be pretty tricky! For a start, you need to choose fish that enjoy the same basic water parameters, eat a similar diet, and will get along together as tank mates.

To complicate matters further, many fish stores advertise fish as being suitable for nano tanks when they actually need a lot more space than that. Fortunately, we have your back!

Read this guide to discover seven of the best fish for small tanks under 10 gallons.

But First …

Before we start talking about these popular fish, please take note of the following important points.

Please do not keep fish in any aquarium smaller than 5 gallons. These extreme nano tanks cannot hold a stable cycle, and you should only keep invertebrates with a small bioload in them.

In addition, you should not keep more than a single fish species in your nano tank to prevent overcrowding and potential territorial aggression.

To keep things interesting, this list contains some suggestions for suitable invertebrates that you could consider adding to your mini-community setup. Invertebrates add interest to your display and can be helpful by grazing on algae, leftover food, and general detritus, keeping your tank clean and tidy.

Nano Fish For Small Tanks

So, here are seven species of fish you can keep in a small tank of less than 10 gallons.

Lyretail Killifish (Aphyosemion Australe)

• Water temperature: 75.2 to 80.6°F
• pH level: 5.5 to 7.0
• Temperament: Peaceful
• Size: 2.5 inches

The Lyretail killifish is a popular choice for smaller aquariums, and these attractive little fish are available in both gold and chocolate color strains.

If your tank is long and relatively shallow, you can keep a pair or trio in an 8 to 10-gallon setup (30 to 38L), provided the tank is very densely planted. Lyretail killifish can live happily in community setups, but most fishkeepers tend to recommend keeping them in species-only tanks to really see them thrive, and that’s the best option in a mini aquarium anyway.

These delightful community fish prefer soft and slightly acidic water, so you can use botanicals and driftwood to get the ideal parameters. Killifishes, as a whole, are known to be accomplished jumpers, so be sure to have a tight-fitting lid or a cover slide for your aquarium!

Unlike many other killifish species, Aphyosemion australe is not annual. That means the beautiful fish can typically live for more than a year, so you don’t have to breed them every year to keep your population intact. In fact, Lyretail killifish can survive for up to three years and are relatively hardy compared to other killies.

Least Killifish (Heterandria Formosa)

• Water temperature: 75 to 79°F
• pH level: 7.0 and over
• Temperament: Peaceful
• Size: 1.2 inches

Although Heterandria formosa is commonly known as “least killifish,” they’re not actually killies at all! These tiny livebearers are super easy to breed, making them a fun species to keep in your nano tank. A “harem” with one male and two females can be kept in tanks as small as 5 gallons (20L), while bigger groups are possible in slightly larger setups.

Because they naturally occur in very slow-flowing waters, Least killifish don’t appreciate a strong filter flow. For best results, try using a filter with a gentler flow (like a sponge filter) and go for a dense plantation to keep your water values stable and imitate the fish’s natural habitat.

Betta Fish (Betta Splendens)

• Water temperature: 70 to 80°F
• pH level: 6.8 to 7.5
• Temperament: Semi-aggressive
• Size: 2.25 inches

Bettas are often marketed as suitable for tiny unfiltered bowls and vases, but nothing could be further from the truth! However, that does not mean they’re not a great choice for small setups, and heated, filtered aquariums of at least 5 gallons (20L) make a great single-fish setup for Betta splendens.

Bettas naturally occur in waters with dense vegetation, so consider using lots of live aquatic plants to imitate the fish’s natural habitat and provide your betta with a place to hide among and rest on. Floating plants like Amazon frogbit are especially appreciated, as their long roots offer plenty of cover, and flat-leaved varieties make ideal betta beds.

If regular old pet store bettas don’t get you excited, why not consider getting one of the many other Betta species that can do well in nano aquariums? For example, Betta mahachaiensis, Betta imbellis, Betta smaragdina, Betta siamorientalis, and Betta stiktos can all be kept in single-fish nano setups as well! Or what about checking out Betta coccina, Betta hendra, or Betta channoides?

The beauty of wild and wild-type bettas is unparalleled, and many fishkeepers prefer the wild species over the fancy domestic varieties.

For more information about betta care, check out our Betta care sheet at this link. If you’re wondering why bettas can’t be kept in a bowl, check out Betta than a bowl, where some of the most urban myths about bettas are smashed!

Sparkling Gourami (Trichopsis Pumila)

• Water temperature: 76 to 82°F
• pH level: 6.0 to 7.0
• Temperament: Semi-aggressive
• Size: 1.5 inches

Many hobbyists who love Bettas are naturally drawn to the beautiful Sparkling gourami, another labyrinth fish. Like Bettas, Sparkling gouramis are small, zippy, and have big personalities! In fact, these fish are so similar in appearance that some people mistake Sparkling gouramis for Bettas with wild coloration.

Since they are similar in size, a single Sparkling can be kept in an aquarium as small as 5 gallons (20L), although it’s always recommended to go larger when possible. If you intend to keep multiple individuals, you’ll need a larger tank with plenty of hiding places since these fish can become aggressive toward each other.

Licorice Gourami (Parosphromenus Deissneri)

• Water temperature: 75 to 82°F
• pH level: 3.5 to 6.5
• Temperament: Peaceful
• Size: 1.5 inches

Licorice gouramis are about the same size as Sparkling gouramis, but the color of the fins on the males makes this species stand out. The fins are bold black and blue, making them easily a centerpiece fish for any setup. However, the striped females look similar to females of other species, so it’s definitely recommended not to mix species to avoid hybridization.

Like Sparkling gouramis, you can keep Licorice gouramis in nano setups, although bigger is better if you want to keep them in pairs or groups. Some hobbyists report keeping pairs in 10-gallon (38L) tanks, although you’ll want to go larger if you plan to raise any fry alongside the parents.

Neon Blue Rasbora (Sundadanio Axelrodi)

• Water temperature: 72 to 76°F
• pH level: 4.0 to 6.5
• Temperament: Peaceful, although males can be aggressive toward each other
• Size: 1 inch

Although these schooling microfish were originally thought to be rasboras, hence their common name, they seem to be more closely related to the Danio family. Their gorgeous bright colors make them a great centerpiece for your nano setup, although many sources report that they are quite fragile and may be picky eaters.

Because these fish should be kept in schools and the males can be aggressive towards each other, I wouldn’t advise keeping them in the smallest possible nano tank, but instead, you should go for something between 8 to 10 gallons (30 to 38L). That makes it possible to keep a slightly larger group, and maintaining good water quality will be easier.

These fish do best in soft, acidic water replicating a blackwater environment. To help make them feel at home, use driftwood and leaf litter, which stains the water. They’re quite popular with shrimp keepers, so if you’re looking for an addition to your dwarf shrimp tank, they may be a good choice.

Asian Stone Catfish (Hara Jerdoni)

• Water temperature: 64 to 75°F
• pH level: 5.5 to 7.5
• Temperament: Peaceful
• Size: 1.4 inches

I hadn’t actually heard of this fish until a reader recently suggested it, and I couldn’t believe they aren’t kept more often! These unusual catfish are peaceful and stay very small, with a maximum of around 3.5 cm (1.4 inches), which means they’re definitely suitable for nano tanks.

Although there isn’t much known about them, it seems that three to four specimens do well in an 8 to 10-gallon (30 to 38L) aquarium because they’re not too active. A carnivorous diet is preferred, and frozen foods are great, but make sure they’re small enough for the fish to eat comfortably.

Final Thoughts

When stocking a nano tank, please always remember that the welfare of your fish is more important than keeping as many species as possible. It’s quite difficult to keep the water values stable in smaller aquariums, so don’t overstock, don’t overfeed your fish, and test the water often.

If you don’t have time to monitor your nano tank, stick with invertebrates! There are many great species to choose from, and they’re typically more tolerant of unstable water conditions than fish.

If you have any more questions about stocking and keeping aquariums under 10 gallons, be sure to leave a comment below.

Happy microfishkeeping!

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