Short answer
Cherry shrimp colony, ember tetras (school of 8-10), pygmy corydoras (school of 6), single male betta with shrimp, sparkling gouramis, white cloud minnows, or a small group of celestial pearl danios. Avoid common goldfish, fancy goldfish, oscars, and any cichlid - all need 30+ gallons.
In depth
The 10-gallon tank is the most common starter tank size. Small footprint (20"x10"x12" typical), affordable to set up ($100-200 total), and supports a meaningful selection of fish. The mistake new keepers make: stocking it with the wrong species - particularly common goldfish, which routinely outgrow 10 gallons within 6 months.
Top livestock for 10 gallons
- Cherry shrimp colony - the easiest livestock period. Self-sustaining colony of 10-30+ specimens. Add to a planted tank with stable parameters and they breed without intervention.
- Ember tetras - school of 8-10 in a planted tank. Tiny (3/4"), peaceful, vibrant orange. Tolerates wide parameter range.
- Pygmy corydoras (Corydoras pygmaeus or hastatus) - school of 6-8 in a sand-bottom tank. Adult size 1", peaceful, schooling.
- Single male betta + cherry shrimp - female bettas are aggressive and not recommended; single male works in 10 gallons with shrimp as tank cleanup.
- Sparkling gouramis (Trichopsis pumila) - pair or trio. Smallest gourami species, peaceful, beautiful labyrinth fish.
- White cloud minnows - school of 6-8. Coldwater tolerant (no heater needed), peaceful, hardy.
- Celestial pearl danios (CPDs) - school of 6-8 in a heavily planted tank. Stunning blue-and-orange coloration.
Avoid in 10 gallons
- Common goldfish, fancy goldfish (need 30+ gallons each)
- Any cichlid (even rams need 20+ gallons)
- Bala sharks, tinfoil barbs, oscars (90+ gallons adult)
- Plecos other than otocinclus (most reach 12-24 inches adult)
- Female bettas, tiger barbs, serpae tetras (aggressive nippers)
More questions
Can I keep neon tetras in a 10-gallon?
Yes, a school of 6-8 neon tetras works in a 10-gallon, but they're less active and colorful than ember tetras at this tank size. Embers tend to look better in smaller spaces.
Is a 10-gallon enough for a goldfish?
No. Common goldfish reach 12+ inches adult and need 30+ gallons minimum. Fancy goldfish reach 6-8 inches and need 20+ gallons. The "1 inch per gallon" rule fails badly with goldfish.