The 25 Best Small Aquarium Fish for Your Freshwater Tank
You’ve learned the basics of keeping a freshwater aquarium and picked out your tank and all the necessary supplies. The only thing left is to choose your fish. Whether you’re a beginner aquarium hobbyist or stocking a community tank, there’s nothing wrong with starting small.
We consulted expert aquarists to compile this list of over two dozen of the best small aquarium fish for freshwater tanks.
The 25 Best Freshwater Fish for Small Aquariums
Many small, freshwater fish thrive in communities—but it’s important to select species with care. Dr. Jessie Sanders, DVM, DABVP, owner of Aquatic Veterinary Services in Santa Cruz, California, encourages hobbyists to choose fish species with compatible temperaments and similar requirements for water chemistry and tank temperature.
1. Endler's Livebearer
- Scientific name: Poecilia wingei
- Adult size: 1–2 inches
- Life expectancy: 2–3 years
- Best tank mates: Small, peaceful fish
Guppies are often top of mind for beginner-friendly freshwater fish—but Endler’s livebearers are equally appropriate. They’re known for being quite hardy, so they may tolerate the inconsistent water parameters common in new tanks. Endler’s livebearers come in a wide range of colors and can be successfully kept (and bred) alongside guppies.
2. Fancy Guppy
- Scientific name: Poecilia reticulata
- Adult size: 1–2 inches
- Life expectancy: 3–5 years
- Best tank mates: Small, peaceful fish
Known for their bright colors and prolific breeding habits, fancy guppies make stunning additions to the community tank. Guppies aren’t schooling fish, so they don’t need to be kept in groups of their own kind—but they’re best kept with other small, peaceful aquarium fish.
3. Swordtail
- Scientific name: Xiphophorus spp.
- Adult size: 3–4 inches
- Life expectancy: 3–5 years
- Best tank mates: Small, peaceful fish
Swordtails come in a wide range of colors and patterns—including spots, stripes, and splotches. Like guppies, swordtails are livebearers that can easily overpopulate a tank if not carefully managed. Mature males are easy to distinguish from females because they grow a swordlike extension on the caudal fin.
4. Platy
- Scientific name: Xiphophorus spp.
- Adult size: 3–4 inches
- Life expectancy: 3–5 years
- Best tank mates: Small, peaceful fish
Platies belong to the same genus as swordtails but lack the swordlike tail extension. These livebearers come in all colors of the rainbow and are generally named for their color or pattern—for example, the wagtail platy is solid-colored with black fins. Other popular patterns include salt-and-pepper, variegated, and tuxedo.
5. Molly
- Scientific name: Poecilia sphenops
- Adult size: 3–5 inches
- Life expectancy: Up to 5 years
- Best tank mates: Small, peaceful fish
Similar in size and body shape to swordtails and platies, mollies exhibit an array of colors. Like betta fish, mollies have been selectively bred for several different fin types—most notably the sailfin molly, which has long, high caudal fins. Though generally hardy, mollies can be challenging for beginners because they prefer hard, alkaline water conditions.
6. Celestial Pearl Danio
- Scientific name: Microrasbora sp. ‘Galaxy’
- Adult size: ~1 inch
- Life expectancy: 3–5 years
- Best tank mates: Small community fish or freshwater shrimp
Also known as the galaxy rasbora—named for the starlike spots covering their bodies—the celestial pearl danio (CPD) is a relatively new entrant to the aquarium hobby. Males are bright blue with red fins, while females are a duller blue-green. CPDs are considered nano fish. Because they’re so tiny, these fish require small foods like baby brine shrimp and micro pellets.
7. Pearl Gourami
- Scientific name: Trichogaster leeri
- Adult size: 3–5 inches
- Life expectancy: 4–5 years
- Best tank mates: Small to medium community fish
One of the hardiest gourami species, the pearl gourami is beginner-friendly and adaptable to a wide range of conditions. These fish have a brown-silver body covered with a pearl-like pattern. Pearl gouramis are peaceful and will thrive in a community planted tank with other tropical species.
8. Neon Tetra
- Scientific name: Paracheirodon innesi
- Adult size: ~1.5 inches
- Life expectancy: 2–5 years
- Best tank mates: Small, peaceful fish
One of the most popular smaller fish for freshwater aquariums, neon tetras are easily identified by the iridescent blue and red stripes running along their bodies. Neon tetras prefer soft, acidic water and should be kept in groups of at least six. Ideal conditions include plenty of aquarium plants and driftwood decorations to mimic their native Amazonian habitat.
9. Betta Fish
- Scientific name: Betta splendens
- Adult size: ~3 inches
- Life expectancy: 2–5 years
- Best tank mates: Active, non-aggressive species
Seen in a wide array of colors, patterns, and fin types, bettas make good beginner fish—with a few caveats. Male bettas are notoriously aggressive and should be kept alone. Depending on your tank size, a single male—or a group of female bettas—may get along with small to medium-sized, active, non-aggressive fish or bottom-feeders.
10. Pygmy Corydoras
- Scientific name: Corydoras pygmaeus
- Adult size: ~1 inch
- Life expectancy: 3–5 years
- Best tank mates: Peaceful community fish
Like other cory catfish, pygmy cories are peaceful bottom-dwellers who do well in community tanks. They help keep water quality high by eating leftover fish food. Their small size and low waste output make them a better fit for small tanks than larger suckermouth catfish like plecos. Pygmy cories can be kept in small groups—but will thrive in a heavily planted tank in a group of 8–12.
11. Golden Wonder Killifish
- Scientific name: Aplocheilus lineatus
- Adult size: 3–4 inches
- Life expectancy: 2–5 years
- Best tank mates: Peaceful middle- and bottom-dwellers
An ornamental variant of the striped panchax, the golden wonder killifish is vibrant yellow with hints of iridescent blue-green. Killifish typically occupy the upper level of the tank, so ideal tank mates include middle- and bottom-dwelling species. Fish keepers should exercise caution when keeping killifish with micro rasboras or other very small fish, as they are predatory. These fish are best kept in small groups in a tank with a tight-fitting lid—they are known to jump.
12. White Cloud Mountain Minnow
- Scientific name: Tanichthys albonubes
- Adult size: ~1.5 inches
- Life expectancy: 3–5 years
- Best tank mates: Peaceful community fish who thrive in cool water
Beyond the realm of tropical fish, some cold-water species—like white cloud mountain minnows—are very beginner-friendly. Unlike goldfish—the quintessential cold-water species—white clouds stay small, so you won’t need to upgrade to a larger tank down the line. White clouds thrive in large groups in a tank with plenty of swimming space where temperatures don’t exceed 72°F.
13. Pygmy Gourami
- Scientific name: Trichopsis pumila
- Adult size: Under 2 inches
- Life expectancy: 3–5 years
- Best tank mates: Peaceful, slow-moving community fish
A compact, gentle gourami species, the pygmy gourami displays subtle iridescence and a calm demeanor. It prefers densely planted tanks with soft, slightly acidic water and does best when housed with similarly peaceful companions—such as ember tetras, harlequin rasboras, or kuhli loaches. Avoid pairing with boisterous or fin-nipping species.
