Common Goldfish

Carassius auratus

Animalia›Chordata›Actinopterygii›Cyprinidae

📍 China (domesticated)

The common goldfish is one of the oldest domesticated fish, kept for over a thousand years. Hardy, cold-tolerant, and long-lived, it is best kept in ponds or large aquariums as it grows substantially. Single-tailed goldfish are active and fast.

Size12"

Min Tank50g

School2+

peaceful

Zoneall

Care Guide

Diet

Common goldfish are omnivores and should be fed high-quality goldfish pellets or flakes as their staple diet, supplemented 2-3 times weekly with vegetables like blanched peas, spinach, and zucchini. Occasional treats of bloodworms or brine shrimp provide protein variety. Feed once daily, only what they can consume in 2-3 minutes, as overfeeding causes water quality issues and health problems.

Behavior

Common goldfish are active, fast swimmers that spend most of their time in the middle to lower water column searching for food. They are peaceful and social, thriving best in pairs or small groups, though they may uproot plants and stir substrate while foraging. They are curious and can recognize their owners, often begging at feeding time.

Breeding

Breeding common goldfish in captivity is possible but requires large tanks (75+ gallons), cooler water temperatures (16-18°C), and seasonal conditioning with live foods. Females scatter thousands of adhesive eggs on plants or spawning mops, and parents will eat eggs and fry if not separated. Fry are difficult to raise and require infusoria or liquid fry food initially.

Tank Mates

Fancy Goldfish

Same species group with compatible water parameters and peaceful temperament; can be housed together in large tanks

excellent

Gold Mystery Snail

Peaceful snail that helps with algae control; goldfish may occasionally harass but snails can retreat into shells

good

Ramshorn Snail

Hardy snail that tolerates goldfish behavior; helps maintain tank cleanliness without competing for food

good

Nerite Snail

Durable snail with hard shell; excellent algae eater that coexists peacefully with goldfish

good

Comet Goldfish

Close relative with identical care requirements and compatible swimming patterns; ideal tank mate

excellent

Common Diseases

Ich (Ichthyophthirius multifiliis)

Symptoms

White spots on body and fins, flashing against surfaces, labored breathing, lethargy

Treatment

Raise temperature gradually to 28-30°C, perform daily 25% water changes, use aquarium salt (1 teaspoon per gallon) or ich medication for 7-10 days

Fin Rot

Symptoms

Frayed or deteriorating fins, discoloration at fin edges, fin shortening over time

Treatment

Improve water quality with frequent changes, remove sharp decorations, treat with antibacterial medication or salt baths; ensure ammonia and nitrite are at 0 ppm

Swim Bladder Disorder

Symptoms

Difficulty maintaining buoyancy, floating at surface or sinking, tilted swimming posture

Treatment

Reduce feeding temporarily, offer blanched peas to aid digestion, maintain stable water temperature, ensure adequate water volume; may be permanent in severe cases

Dropsy

Symptoms

Swollen belly, pinecone-like scales, lethargy, loss of appetite, pale gills

Treatment

Isolate fish immediately, perform frequent water changes, treat with antibiotics if bacterial; prognosis is poor; maintain pristine water conditions to prevent occurrence