Best Fish for a 20 Gallon Tank: Top Picks and 3 Stocking Plans
Published: 2026-10-29 · FishyKart Blog
A 20 gallon (76 liter) tank is the size where a real community becomes possible: the best fish include harlequin rasboras, neon tetras, a honey gourami group or one dwarf gourami, plus corydoras or kuhli loaches on the bottom. That usually means one or two schools of small fish, a centerpiece and a bottom group. Below are the top picks and three stocking plans you can copy.
Photo: Netha Hussain - Wikimedia Commons, CC0
Top Picks for a 20 Gallon Tank
| Species | Adult size / Group in 20 gal (76 L) |
| Harlequin rasbora | 1.5-2 in / school of 8-10 |
| Neon tetra | 1.2-1.5 in / school of 10-15 |
| Ember tetra | 0.8 in / school of 10 or more |
| Honey gourami | 1.5-2 in / pair or small group |
| Dwarf gourami | about 3.5 in / 1 male as centerpiece |
| Panda cory or other corydoras | about 2 in / group of 6-8 |
| Kuhli loach | 3-4 in, very slim / group of 5-6 |
| Otocinclus | 1.2-2 in / group of 6 |
| Cherry barb | 1.5-2 in / school of 6 or more |
| Male guppies | 1.5 in / small male group |
Sizes are typical adult ranges; individual fish vary.
Schooling Fish
Harlequin rasboras are calm, hardy and stay in a loose group in mid-water, which makes them one of the best 20 gallon schooling fish. Neon tetras need a cycled, stable tank but finally get a proper school of 10 or more here. Ember tetras are the choice for a heavily planted nano-style layout. Cherry barbs add red color and are peaceful when kept in a group.
Centerpiece Fish
- Honey gourami: small, gentle and less aggressive than the dwarf gourami. A pair or small group suits 20 gallons.
- Dwarf gourami: brighter colors but males can be territorial, so keep only one male.
- Betta: possible in a peaceful community with short-finned, calm fish, never with fin nippers.
Bottom Dwellers
Corydoras need a group of 6 or more and soft sand to protect their barbels. Kuhli loaches need a group of 5 or more and hide in sand and plants during the day. Otocinclus graze algae film but need a mature tank and extra algae wafers. A 20 gallon long gives more floor space for all three.
3 Stocking Plans for 20 Gallons
- Classic community: 10 harlequin rasboras + 6 corydoras + 2 nerite snails. Easy, peaceful and forgiving for beginners.
- Gourami planted tank: 1 dwarf gourami or 3 honey gouramis + 10 ember tetras + 5-6 kuhli loaches, at about 76-78 F (24-26 C), with dense and floating plants to calm the gouramis.
- Neon showcase: 12-15 neon tetras + 6 otocinclus + cherry shrimp, in a planted tank kept at about 75-78 F (24-26 C).
Add fish in small batches over several weeks, and check ammonia and nitrite after each batch. Before the first fish, cycle the tank.
What Not to Keep in a 20 Gallon
- Common plecos, oscars, bala sharks and red tail catfish: all outgrow 20 gallons.
- Goldfish: they need far more water than a tropical community of the same length.
- Angelfish: they grow tall and are better in taller, larger tanks; they may also eat neon tetras.
- Tiger barbs and serpae tetras with gouramis or bettas: fin nipping.
- Two male dwarf gouramis or two male bettas.
Smaller tank? See the best fish for a 10 gallon tank.