Common goldfish care guide

Plan a tank with common goldfishSee all tank mates

Common goldfish quick facts

• Cold-water species: no heater needed in most homes.
• Known jumper: keep a tight-fitting lid.

Tank setup

One adult needs at least 75 gallons (284 L) in a tank 4 ft (120 cm) or longer, and a group needs more. A large pond is the best long-term home for most. Keep decor smooth and simple to leave open swimming space, and use a lid, since comets can jump.

How many common goldfish in a tank?

The smallest common tank that suits common goldfish is a 75 gallon. Here is roughly how many fit in each size when they are the only fish, based on adult size and waste output. Leave room if you want tank mates.

Water parameters

They do best at about 15–22 °C (59–72 °F), pH 6.5–8.0 and moderately hard water, with no heater in most homes. They make a lot of waste, so use filtration rated well above the tank size and change 30–50% of the water when nitrate climbs. Good surface movement keeps oxygen high.

Best tank mates for common goldfish

These popular species share common goldfish' water needs and temperament. See the full list of 7 good matches.

• Hillstream loach

  6.5 cm (2.6 in) · 20–24°C (68–75°F)

• Rosy barb

  9 cm (3.5 in) · 18–24°C (64–75°F)

• Dojo loach

  15 cm (5.9 in) · 18–23°C (64–73°F)

• Paradise fish

  8 cm (3.1 in) · 16–24°C (61–75°F)

• Buenos Aires tetra

  7 cm (2.8 in) · 18–25°C (64–77°F)

• Gold barb

  7 cm (2.8 in) · 18–24°C (64–75°F)

• Variatus platy

  6 cm (2.4 in) · 18–25°C (64–77°F)

Avoid keeping common goldfish with

• Angelfish: They need different temperatures: Common goldfish 15–22°C (59–72°F), angelfish 24–29°C (75–84°F).
• Betta fish: They need different temperatures: Common goldfish 15–22°C (59–72°F), betta fish 24–28°C (75–82°F).
• Cherry shrimp: Common goldfish eats small shrimp like cherry shrimp.
• Common pleco: They need different temperatures: Common goldfish 15–22°C (59–72°F), common pleco 23–28°C (73–82°F).
• Dwarf gourami: They need different temperatures: Common goldfish 15–22°C (59–72°F), dwarf gourami 24–28°C (75–82°F).
• Neon tetra: Common goldfish can eat neon tetras: they're small enough to fit in its mouth once it's grown.

Feeding

Feed a goldfish pellet or flake as the staple, with frozen brine shrimp or daphnia and greens such as peas or duckweed. Give only what they finish in a couple of minutes, once or twice a day. Hungry commons will graze on most soft plants.

Behavior

Peaceful, social and very active. They do best with other commons, comets or shubunkins, not slow fancy goldfish, which they beat to food and sometimes nip. They eat shrimp, fry and fish small enough to swallow. In big tanks, dojo loaches, hillstream loaches and rosy barbs can make good tankmates.

Breeding

Commons spawn easily in ponds in spring as the water warms. Males grow white bumps on the gill covers and front fins and chase the females. The sticky eggs land on plants and are eaten by the adults, so dense plants or a separate tank are needed to raise fry. Never release extra fish into the wild.

Tips from experienced keepers

• Never release goldfish into lakes or streams. They grow large, breed fast and harm native wildlife.
• Plan for a pond or a tank of 75 gallons (284 L) or more. Small shop fish grow quickly.
• Keep them apart from fancy goldfish, which can't compete with them for food.
• Use tough plants like anubias and java fern tied to rock or wood.
• Fit a lid. Comets especially can jump when startled.

Sources

We checked these references when writing this page. Values are for healthy long-term keeping, not survival limits. Last reviewed 2026-10-13. See our editorial policy.

• fishbase.se
• aquariumcoop.com
• aquariumcoop.com
• articles.hepper.com
• ornamentalfish.org