Goldfish — Fish Profile
Carassius auratus
Quick Specs
| Adult Size: | 10.0" |
| Temperament: | peaceful |
| Care Level: | beginner |
| Min Tank Size: | 30 gallons |
| Temperature: | 62-74°F |
| pH Range: | 6.5-7.5 |
| Diet: | omnivore |
| Origin: | East Asia (China) |
| Lifespan: | 10-15 years |
Overview
Goldfish are one of the most popular freshwater fish in the world. They are coldwater fish that produce a lot of waste and need larger tanks than most people realize. Common goldfish can grow to 10+ inches.
Care Guide for Goldfish
Tank Setup
Goldfish requires a minimum tank size of 30 gallons. Maintain water temperature between 62°F and 74°F, with a pH range of 6.5 to 7.5. A properly sized tank with adequate filtration and regular water changes is essential for long-term health. When housing Goldfish with other species, always choose a tank size that accommodates the most demanding fish in the community.
Feeding
Goldfish is a omnivore feeder. Provide a varied diet appropriate for omnivore species to ensure optimal health and coloration. Feed small portions 2–3 times daily, and remove uneaten food after a few minutes to maintain water quality.
Temperament & Compatibility
This species is classified as peaceful. Goldfish reaches an adult size of 10.0 inches and has a care level of beginner. Always research compatibility before adding new fish to an established aquarium. Individual temperament can vary, so monitor new introductions closely for the first 48 hours.
Origin & Lifespan
Goldfish originates from East Asia (China) and has an expected lifespan of 10-15 years when kept in proper water conditions with appropriate tank mates and diet.
Compatible Tank Mates
🟢 Good Tank Mates
🟡 Caution Tank Mates
🔴 Risky Tank Mates
Compatibility Results for Goldfish
All 69 compatibility checks involving Goldfish:
Expert Care Tips for Goldfish
- Mid-size tank: Goldfish needs 30+ gallons. Choose a tank at least 2× as long as the fish's adult size (10.0") for adequate swimming room.
- Cool-water species: Goldfish tolerates temperatures as low as 62°F. In most homes, no heater is needed, but watch for summer overheating above 74°F.
- Narrow pH tolerance: Goldfish only tolerates pH 6.5–7.5. Test your tap water before buying — adjusting pH is harder than choosing the right fish for your water.
- Peaceful community fish: Goldfish works well in community tanks. Still, avoid housing with fish large enough to eat them — a 10.0" fish is vulnerable to anything with a mouth bigger than 2×.
- Acclimation: Always drip-acclimate Goldfish over 30–45 minutes. Match temperature and pH gradually to prevent osmotic shock.
Tools & Resources
⚠️ Goldfish Diseases: Swim Bladder, Ich & Fin Rot Guide
Goldfish are notoriously prone to disease due to their high waste production and the common mistake of keeping them in undersized tanks. Their round body shape makes swim bladder issues especially prevalent in fancy varieties, and their coldwater environment means some medications work differently than in tropical tanks.
Swim Bladder Disease
Symptoms: Fish floating at surface upside-down; sinking to bottom unable to rise; listing to one side; difficulty maintaining position; bloated appearance; may still eat normally
Treatment: Fast the fish for 3 days, then feed deshelled green peas (natural laxative). Lower water level to reduce swimming effort. Maintain temperature at 68-72°F. Add Epsom salt (1/8 tsp per 5 gallons). Avoid floating pellets — switch to sinking goldfish food. Swim bladder issues in fancy goldfish are often chronic due to their compressed body shape — management, not cure, is the realistic goal.
Ich (White Spot Disease)
Symptoms: White salt-like spots on body and fins; rubbing against objects; clamped fins; lethargy; increased mucus; rapid breathing
Treatment: Raise temperature to 74-76°F (goldfish tolerate lower temps — do NOT go above 78°F). Treat with malachite green at half dose (goldfish are sensitive to medications). Add aquarium salt (1 tsp per gallon). Perform daily 25% water changes. Goldfish ich takes longer to treat at lower temperatures — continue for 14-21 days. Avoid copper medications with goldfish.
Fin Rot
Symptoms: Fins appearing frayed, ragged, or dissolving from edges; whitish or reddish fin edges; fins progressively shortening; inactivity; may accompany red streaks on body
Treatment: Immediate 50% water change and test ammonia/nitrite (goldfish waste makes fin rot almost always water-quality related). Treat with antibiotic (Kanamycin or Furan-2). Add aquarium salt (1 tsp per gallon). Clean or replace filter media. Goldfish fin rot recovers slowly — expect 6-10 weeks for fin regrowth. Address the root cause: upgrade filtration and increase water change frequency.
Always quarantine sick fish and consult an aquatic veterinarian for persistent health issues.