Best Fish for a 20 Gallon Tank
A proper community of two schools plus a centerpiece fish.
31 species in our database can live in a 20-gallon tank. Here are some stocking ideas.
Schooling fish
Centerpiece & bottom dwellers
Frequently asked questions
What fish can live in a 20 gallon tank?
31 species from our database can live in a 20-gallon tank. This includes 14 schooling species and 10 centerpiece/bottom dwellers.
How many fish can I put in a 20 gallon tank?
Use our stocking calculator to estimate a safe stocking level based on fish size and bioload. A 20-gallon tank gives you 76 liters of volume.
Related resources
Calculate exact stocking for 20 gal →
Species that fit a 20 gallon tank
All 14 species below have a minimum tank size of 20 gallons or less. Remember that minimum group size is part of the calculation — a shoaling species needs room for the whole group, not one fish.
| Species | Adult size | Min tank | Group | Temperature |
|---|---|---|---|---|
| Swordtail | 5.5″ | 20 gal | 3+ | 72–82°F |
| Kribensis | 4.0″ | 20 gal | 1+ | 75–82°F |
| Kuhli Loach | 4.0″ | 20 gal | 5+ | 75–86°F |
| Molly | 4.0″ | 20 gal | 3+ | 72–82°F |
| Dwarf Gourami | 3.5″ | 10 gal | 1+ | 72–82°F |
| Apistogramma | 3.0″ | 20 gal | 1+ | 75–83°F |
| Bolivian Ram | 3.0″ | 20 gal | 1+ | 72–79°F |
| Tiger Barb | 3.0″ | 20 gal | 8+ | 74–82°F |
| Betta | 2.5″ | 5 gal | 1+ | 76–82°F |
| Bronze Corydoras | 2.5″ | 20 gal | 6+ | 72–79°F |
| German Blue Ram | 2.5″ | 20 gal | 1+ | 78–85°F |
| Platy | 2.5″ | 10 gal | 3+ | 70–82°F |
| Amano Shrimp | 2.0″ | 10 gal | 3+ | 65–80°F |
| Cardinal Tetra | 2.0″ | 20 gal | 6+ | 73–81°F |
20 gallon tank FAQ
How many fish can I keep in a 20 gallon tank?
It depends on the species. As a guide, a 20-gallon tank comfortably supports two to three species spread across swimming zones. Use the stocking calculator for a specific plan.
Does a 20 gallon tank need a filter and heater?
A filter, always — it houses the bacteria that process fish waste. A heater is needed unless you keep coldwater species; see fish that do not need a heater.
How often should I change the water in a 20 gallon tank?
25–30% weekly, which is about 5 gallons. Consistency matters more than volume.