There are many small freshwater fish under 2 inches perfect for nano tanks. Popular species include Chili Rasboras, Endler’s Livebearers, and Celestial Pearl Danios. They’re peaceful, colorful, and easy to care for in 5–10 gallon aquariums.
What Makes a Fish Ideal for Small Aquariums?
- Adult size remains under 2.5 inches
Peaceful temperament to reduce stress - Adapts well to limited swimming space
- Does not overload the tank’s bio-capacity
➡️ Tip: A nano tank can still be vibrant if you choose the right species and avoid overcrowding.
15 Small Fish for Nano Tanks (Under 2.5 Inches)
1. Endler’s Livebearer
Endlers are tiny, vibrant fish that stay under 1.5 inches. Active and peaceful, they do best in groups and are great for 5–10 gallon tanks.
2. Chili Rasbora
Measuring around 0.7 inches, Chili Rasboras are among the smallest freshwater fish. They prefer planted tanks and thrive in peaceful shoals.
3. Ember Tetra
These fiery orange fish stay under an inch long and look stunning in planted tanks. Keep them in schools of six or more.
4. Celestial Pearl Danio (Galaxy Rasbora)
Compact and eye-catching, these galaxy-spotted fish enjoy calm nano setups. Keep them in groups with hiding spots.
5. Pygmy Corydoras
Pygmy corys are friendly bottom dwellers that reach about an inch in size. Keep them in groups of 4–6 for best activity.
6. Otocinclus Catfish
Otocinclus are efficient algae eaters and stay around 1.5 inches. They’re peaceful and great companions in planted tanks.
7. White Cloud Mountain Minnow
These adaptable fish tolerate cooler temps and do well in groups. They max out at 1.5 inches and suit 10-gallon setups.
8. Green Neon Tetra
Smaller than common neon tetras, these glow brightly in planted nano tanks. Schooling is a must.
9. Scarlet Badis
Stunning yet shy, these micro predators need live foods and gentle tank mates. Best kept alone or in species-only setups.
10. Dwarf Pencilfish
Peaceful and top-dwelling, these slim fish stay under 1.5 inches. Keep them in calm, planted tanks.
11. Sparkling Gourami
This small labyrinth fish has shimmering scales and a calm nature. Can be kept singly or in peaceful pairs.
12. Least Killifish (Heterandria formosa)
One of the smallest livebearers, these stay under 1 inch. Hardy and easy to breed in nano tanks.
13. Neon Tetra
While larger than others listed, small groups of neon tetras work well in 10-gallon tanks with calm tank mates.
14. Guppy
Male guppies stay under 1.5 inches and bring constant motion to small aquariums. They’re easy to care for and breed.
15. Harlequin Rasbora (Juveniles)
Juvenile harlequin rasboras adapt well to 10-gallon tanks and display calm, schooling behavior.
Fish to Avoid in Small Tanks
Some species may seem appealing but are unsuitable for nano tanks due to size or behavior:
- Goldfish – Grow large and produce excess waste
- Common Plecos – Can reach 12+ inches
- Tiger Barbs – Nippy and too fast for small tanks
- Angelfish – Require height and ample space
Stocking Tips for 5–10 Gallon Aquariums
- Stick to one school or compatible species in smaller tanks
- Avoid overcrowding — balance swimming space and hiding spots
- Use sponge or low-flow filters to prevent stress
- Add floating or live plants to increase comfort and reduce aggression
Nano Tank Combo Ideas
5-Gallon Tank
- 6 Chili Rasboras
- 1 Amano Shrimp
- Floating hornwort or moss for cover
10-Gallon Tank
- 6 Ember Tetras
- 3 Otocinclus
- 1 Sparkling Gourami
- Dwarf hairgrass or java fern for natural filtration
Final Thoughts
A nano tank can be just as exciting and beautiful as a larger setup. With the right small fish, you can build a peaceful, balanced, and low-maintenance aquarium that’s full of life. Stick to truly small species, keep conditions stable, and enjoy the charm of your miniature underwater world.
➡️ For more inspiration, visit our full Freshwater Fish Guide.
