We are thrilled to share our top 10 selections of nano fish that thrive in nano aquariums and look stunning. The reason for our excitement is simple: the recent surge in interest in nano aquaristics has led to a greater variety of nano fish species. This diversity is fantastic for the aquarium hobby, though it can also make it harder to navigate the extensive range of options. Therefore, having a curated list can be quite useful. Before we dive into our top 10 nano fish, we’d like to provide some essential information for beginners about keeping nano fish.
Essential Information on Keeping Nano Fish
When the nano aquarium hobby began in the mid-2000s, the selection of suitable nano fish was quite limited. Smaller aquariums were mostly populated by shrimp and snails, as the freshwater fish market offered few species that could thrive in such confined spaces. The most popular fish at the time required more room than nano aquariums could provide.
Fortunately, this situation has improved significantly. Today, the aquarium fish market offers a wider variety of species that can thrive in nano aquariums ranging from 30 to 60 liters. Many of these species stay under 2.5 cm and can live comfortably, often in groups, in a 30+ liter planted aquarium. It is important to note that nano aquariums with less than the recommended minimum volume of 30 liters are not suitable for keeping fish permanently.
Why? One key reason is that fish have a more active metabolism than shrimp, leading to greater water pollution in the aquarium. The health risks for the fish increase as the aquarium’s volume decreases because smaller volumes are more susceptible to fluctuations in biological stability.
Establishing good technical filtration is crucial to maintaining a stable ecosystem in a nano aquarium. Additionally, it requires aquatic plants, a suitable substrate, and hardscape elements like stones or roots. These items can be colonized by beneficial bacteria that help break down pollutants. For these bacteria to function effectively, they need oxygen. A well-maintained filter flow should ensure adequate movement of the water surface, enhancing gas exchange between the water and the air.
Regular water changes are also vital, with at least 50% of the water being changed once a week, or even better, 30% twice a week, to reduce pollutant levels.
The amount of fish food should be carefully controlled to ensure most of it is consumed and doesn’t decompose at the bottom, unnecessarily polluting the water. Feed only what the fish can eat in 2-3 minutes, adding small amounts gradually so the fish can absorb the food before it sinks.
Guidelines for Determining the Number of Fish
A general guideline in the freshwater aquarium hobby is to allow 1 cm of fish per liter of water. For example, if you have a 60-liter aquarium and choose a fish species that grows to a maximum length of 2.5 cm, you would use the following calculation:
60 liters ÷ 2.5 cm per fish = 24 fish
Therefore, if you plan to keep only this species in your 60-liter aquarium, 24 fish would be a suitable number.
Here's the top 10 Nano Fish
1. Betta splendens - Siamese fighting fish
The Betta splendens stands out as one of the most stunning and captivating fish in the nano category. Typically, it’s advised to keep Betta as solitary fish, unlike many other nano species that thrive in groups. However, the Betta splendens doesn’t depend on numbers; it’s bold and visible, constantly active under light, asserting its dominance in the aquarium. While it’s possible to keep a Siamese fighting fish with other peaceful, smaller species, this demands a larger tank and experience with Bettas. For beginners, a 30-liter nano cube with a single Betta is the safer choice.
Size full grown: 5.0 – 8.0 cm
Aquarium size: Minimum 30 liters; not exceeding 30 cm in height
Temperature: 24 – 28°C
pH: 6.5 – 7.5
Behavior: Territorial
Food: Prefers live or frozen food, but can adapt to granule food
Nano aquarium mates: Snails and shrimp
Baby shrimp suitability: If a shrimp can fit into the Betta’s mouth, it’s on the menu.
When introducing other livestock with a Betta, prioritize the safety of the other creatures. Due to their territorial nature, Siamese fighting fish may be aggressive towards newcomers, making them more vulnerable upon arrival.
2. Neon blue rasbora - Sundadanio axelrodi
The Neon blue rasbora is a lively, tranquil fish, boasting a stunning neon blue hue, as its name implies. Perfect for planted tanks, it thrives in pristine water conditions, which is why it’s not typically recommended for beginners. However, meeting its care needs is rewarding, as it ranks among the most delightful nano fish in both appearance and demeanor.
Size full grown: 2.0 – 2.2 cm
Aquarium size: Minimum volume of 36 liters with base dimensions of at least 45cm x 27cm
Temperature: 23 – 26°C
pH: 5.0 – 7.0
Behavior: Peaceful, shoaling
Food: Prefers live or frozen food, may accept dry food
Nano aquarium mates: Compatible with snails and shrimp
Baby shrimp suitability: Suitable for baby shrimp
3. Neon-green rasbora - Microdevario kubotai
The Neon blue rasbora is a lively, tranquil fish, boasting a stunning neon blue hue, as its name implies. Perfect for planted tanks, it thrives in pristine water conditions, which is why it’s not typically recommended for beginners. However, meeting its care needs is rewarding, as it ranks among the most delightful nano fish in both appearance and demeanor.
Size full grown: 1.5 – 2.0 cm
Aquarium size: Base dimensions measuring at least 60cm x 30cm
Temperature: 20 – 27°C
pH: 6.5 – 7.2
Behavior: Shoaling, peaceful
Food: Omnivorous, all common food types
Nano aquarium mates: Snails and shrimp
Baby shrimp suitable: Yes
4. Celestial pearl danio - Danio margaritatus
This mesmerizing nano fish, also called a Galaxy danio, boasts a stunning spotted body pattern. Males stand out with vividly red, patterned fins against their dark bodies, while females sport paler orange fins of equal charm. Initially shy, Pearl danios prefer hiding in plant thickets or hardscape gaps but gradually grow bolder, adding life to the aquarium.
Size full grown: 2.0 – 2.5 cm
Aquarium size: Base dimensions measuring at least 45cm x 27cm and a min. 36 liters volume
Temperature: 18 – 26°C
pH: 6.5 – 7.5
Behavior: Shoaling, peaceful; due to the sometimes-combative behavior of dominant males among themselves, we recommend aiming for a 1 to 3 ratio (male/female) whenever possible.
Food: Omnivorous, should get a varied diet, including live and frozen food
Nano aquarium mates: Snails and shrimp
Baby shrimp suitable: Yes
5. Mosquito rasboras - Boraras brigittae
Boraras brigittae exhibit a striking red coloration with bold black stripes, which intensifies when they’re healthy and thriving. Originating from blackwater habitats, they prefer soft, acidic water rich in humic substances.
Size full grown: 1.5 – 2.0 cm
Aquarium size: Base dimensions measuring at least 45cm x 27cm and a min. 36 liters volume
Temperature: 20 – 28°C
pH: 5.0 – 6.5
Behavior: Shoaling, peaceful
Food: Omnivorous, all common food types
Nano aquarium mates: Snails and shrimp
Baby shrimp suitable: Yes
6. Emerald dwarf danio - Danio erythromicron
Closely related to the beloved Celestial pearl danio, the Emerald dwarf danio shares a similar physique but boasts distinct markings. Adorned with deep blue longitudinal stripes complemented by reddish hues, it presents a stunning appearance. While slightly less timid, it thrives best in groups of at least ten companions. It coexists harmoniously with shrimp capable of tolerating slightly harder water conditions.
Size full grown: 1.5 – 2.0 cm
Aquarium size: Base dimensions measuring at least 45cm x 27cm and a min. 36 liters volume
Temperature: 20 – 25°C
pH: 7.0 – 8.0
Behavior: Shoaling, peaceful
Food: Omnivorous, all common food types
Nano aquarium mates: Snails and shrimp
Baby shrimp suitable: Yes
7. Ember tetra - Hyphessobrycon amandae
This bright red tetra inhabits small rivers and flooded lakes with humusy and soft water and is the only fish on our list originating from South America. All others are Asians.
Like all Characin, the Ember tetra is predatory but is characterized by its peacefulness. It can even be kept together with dwarf shrimps, as, at most, the tiniest baby shrimps fit into its small mouth. Shrimp species such as Neocaridina davidi are best suited for socialization.
Size full grown: 1.5 – 2.0 cm
Aquarium size: Base dimensions measuring at least 60cm x 30cm
Temperature: 23 – 28°C
pH: 5.5 – 7.0
Behavior: Shoaling, peaceful
Food: Omnivorous, should get a varied diet, including live and frozen food
Nano aquarium mates: Snails and shrimp
Baby shrimp suitable: Most baby shrimp will survive if there are enough hiding places (aquarium densely planted and mosses).
8. Phoenix rasbora - Boraras merah
With the primary red color and a distinctive black spot, the attractive Phoenix rasbora belongs to the Cyprinidae family, just like the popular Mosquito rasbora. Although small, it requires a relatively large swimming space for its well-being.
Size full grown: 1.5 – 2.0 cm
Aquarium size: Base dimensions measuring at least 45cm x 27cm
Temperature: 20 – 28°C
pH: 4.5 – 6.0
Behavior: Shoaling, peaceful
Food: Omnivorous, all common food types
Nano aquarium mates: Snails and shrimp
Baby shrimp suitable: Yes
9. Exclamation point rasbora - Boraras uropthalmoides
The Exclamation Mark Rasbora is a social aquarium dweller, albeit one of the more reserved species. Ideally, it thrives in larger groups, with a minimum starting size of ten fish. However, it truly flourishes in groups exceeding twenty, encouraging them to explore the open swimming area more frequently. Among nano fish, Boraras uropthalmoides stands out as a true gem. While other Boraras species tend to have reddish hues and form loose groups, the Exclamation Point Rasbora distinguishes itself with vibrant golden-orange and shimmering black stripes, displaying intense schooling behavior.
Size full grown: 1.5 – 2.0 cm
Aquarium size: Base dimensions measuring at least 60x30x30 cm / 54 liters
Temperature: 22 – 26°C
pH: 5.0 – 6.5
Behavior: Schooling, peaceful
Food: Omnivorous, all common food types
Nano aquarium mates: Snails and shrimp
Baby shrimp suitable: Yes
10. Dwarf puffer fish - Carinotetraodon travancoricus
The Dwarf puffer fish stands out as a captivating species, distinct in appearance from other nano fish on our list. They possess unique preferences and require more specialized care, particularly regarding their dental needs. In their natural habitat, they encounter ample crunchy foods to grind down their constantly growing teeth. However, in aquarium settings, they rely on daily feeding, such as crunchy snails, to maintain dental health. Due to their predatory nature, they are often housed in species-only tanks. In the wild, these dwarfs form large shoals, so for long-term care, a group of at least 8-10 fish is recommended. For further information on Dwarf puffer fish, follow the link provided.
Size full grown: 1.5 – 2.0 cm
Aquarium size: Base dimensions measuring at least 60cm x 30cm
Temperature: 23 – 28°C
pH: 6.0 – 8.0
Behavior: Shoaling, predatorial
Food: Carnivorous, live and frozen food, such as tiny snails (crunchy food for tooth care), mosquito larvae, daphnia, or bloodworms
Nano aquarium mates: Otocinclus Affinis
Baby shrimp suitable: No
Additional Guidelines for Ensuring the Well-being of Nano Fish
In addition to the diet composition, ensuring that the food is small enough for the nano fish to ingest is crucial. Special flakes and granulated food in nano size cater to the smallest fish mouths.
Shoaling and schooling fish thrive best in larger groups, exhibiting more natural behavior. The mantra seems to be “the more, the merrier,” without overcrowding.
Dense planting is essential for maintaining species-appropriate nano fish habitats. In nature, smaller fish seek shelter in dense vegetation to hide from predators. While wise fish selection can prevent predatory incidents, providing sheltering facilities enhances fish well-being, as they retain their natural habits and preferences.
Nano cubes have become popular in the aquarium hobby, but there’s a caveat. Despite their appeal, 30-liter or smaller nano cube aquariums offer limited options for fishkeeping, as evident from our top 10 list. While suitable for Betta splendens, shrimp, and snails, most nano fish species do not thrive in such environments in the long run.
Comparatively, rectangular aquariums provide better swimming space for fish, especially for more active species with pronounced swimming behaviors.
