Common goldfish

Overview

The common goldfish is the world's oldest domesticated fish, bred in China more than a thousand years ago from the Prussian carp. It has a streamlined body, a short forked tail and colors ranging from bright orange to red, yellow, white or mixed patterns.

Its reputation as an "easy" fish is only half true. It is extremely hardy and needs no heater, but it grows far bigger than most people expect: a healthy fish passes 8 inches (20 cm) and can live 15 to 20 years. It is active, learns to recognize whoever feeds it and is ideal for a large coldwater aquarium or, better still, a backyard pond. The one thing it should never be is a bowl fish.

Care and tank setup

Forget the bowl: it is tiny, cannot hold a proper filter and ammonia builds up within hours. A pair of common goldfish needs at least 75-80 gallons (300 L), and once they mature the ideal home is a pond of several hundred gallons or more.

• Filtration: goldfish are messy. Use a canister or pond filter that turns over the volume several times per hour, and change 30-50% of the water weekly.
• Temperature: cool water, no heater. Pond fish overwinter safely with 30-40 inches (80-100 cm) of depth and a surface that never freezes solid.
• Decor: smooth gravel or sand, large rocks and tough plants (anubias, Java fern, elodea) or artificial ones, since goldfish dig and eat tender greenery.

They get along with other common and comet goldfish, but not with slow fancy varieties, which lose out at feeding time, nor with tropical fish. Most important: never release goldfish into rivers, lakes or storm ponds; they are invasive and harm native wildlife.

Feeding

Goldfish are greedy omnivores. Use a quality goldfish pellet as the staple (sinking or pre-soaked is best) and add blanched vegetables such as shelled peas, zucchini or spinach, plus frozen brine shrimp or bloodworms. Feed only what they finish in one to two minutes, once or twice a day. Overfeeding is the most common mistake and leads to cloudy water and digestive trouble.

Breeding

They spawn mainly in ponds in spring as the water warms. Males develop white breeding tubercles on the gill covers and chase females until they scatter hundreds of sticky eggs among plants. Parents eat the eggs, so anyone hoping to raise fry must remove the egg-covered plants. Think it through first: every spawn produces lots of fry that need room and a responsible home.

Compatible tank mates

Species from our database that share water parameters, size and temperament with the Common goldfish. Calculated from the data in each profile.

Check the compatibility of your whole tank →

What not to keep it with

Popular species you shouldn’t house with the Common goldfish, and why.

• Cherry barb: incompatible temperatures, one may eat the other due to size
• Panda cory: one may eat the other due to size
• Zebra danio: one may eat the other due to size
• Discus: incompatible temperatures
• Guppy: one may eat the other due to size
• Clown loach: incompatible temperatures
• Oscar: incompatible temperatures, incompatible temperaments
• Otocinclus catfish: one may eat the other due to size

Recommended equipment

What you need to keep the Common goldfish healthy, checked against Amazon stock.