Goldfish

Goldfish are one of the most iconic and misunderstood aquarium fish. Despite common misconceptions, they are not suitable for bowls or small tanks. These hardy fish can live 10-15 years and grow quite large. They are coldwater fish that produce significant waste, requiring proper filtration and regular maintenance. Goldfish come in many varieties including Common, Comet, Fantail, Oranda, and Ranchu.

Care Requirements

Tank Setup

Minimum tank size: 20 gallons for one fancy goldfish, 30+ for single-tail varieties. Add 10 gallons for each additional fish.

Critical Requirements:

• Powerful filtration (they are messy!)
• No heater needed (coldwater fish)
• Large surface area for oxygen exchange
• Smooth decorations (some varieties have delicate fins)
• No sharp gravel (they like to forage)

Water Quality

• Temperature: 65-75°F (18-24°C) - room temperature is fine
• pH: 7.0-8.4 (they prefer slightly alkaline water)
• Water Hardness: Moderate to hard (8-20 dGH)
• Ammonia/Nitrite: 0 ppm (extremely sensitive)
• Nitrate: <40 ppm

Goldfish produce a lot of waste, so:

• Use oversized filtration (2-3x tank volume per hour)
• Perform 30-50% water changes weekly
• Monitor ammonia levels closely

Feeding

Goldfish are omnivores but need plant matter:

• Staple: High-quality goldfish pellets (sinking preferred)
• Vegetables: Blanched peas, zucchini, spinach, lettuce
• Protein: Frozen bloodworms, brine shrimp (occasionally)
• Avoid: Tropical fish flakes (not enough nutrients)

Feeding Schedule: 2-3 times daily, small amounts they can eat in 2 minutes. Fast one day per week.

Behavior & Compatibility

Goldfish are peaceful but have specific requirements:

• Best with: Other goldfish of similar size and variety
• Can work with: Coldwater species like White Cloud Mountain Minnows, Dojo Loaches
• Never with: Tropical fish (temperature mismatch)

Important: Single-tail goldfish (Comet, Common) are fast swimmers that may outcompete fancy varieties for food. House similar types together.

Common Health Issues

1. Swim Bladder Disease: Often from overeating or constipation; feed peas
2. Ich: White spots; treat with temperature adjustments and medication
3. Fin Rot: Poor water quality; improve filtration and water changes
4. Dropsy: Bloated appearance with raised scales; often fatal, poor prognosis
5. Flukes: Parasites causing scratching; treat with anti-parasitic medication

Goldfish Varieties

Hardier/Beginner-Friendly:

• Common Goldfish (can grow 12+ inches)
• Comet Goldfish (slender, fast swimmers)
• Shubunkin (calico colors)

Fancy Varieties (more delicate):

• Fantail (double tail, egg-shaped body)
• Oranda (wen growth on head)
• Ryukin (humped back)
• Ranchu (no dorsal fin)
• Bubble Eye (fluid-filled eye sacs)

Size Considerations

Goldfish grow throughout their lives:

• First year: Can reach 2-4 inches
• Mature size: 6-12 inches depending on variety
• Lifespan: 10-15 years with proper care

Never keep in bowls - this stunts their growth and causes health issues.

Tank Maintenance

Due to their waste production:

• Weekly 30-50% water changes
• Vacuum gravel during water changes
• Clean filter media monthly (in tank water, not tap)
• Test water parameters weekly
• Prune plants regularly (they eat them!)

Tips for Success

• Buy the biggest tank you can afford
• Invest in quality filtration
• Feed sinking pellets to prevent swim bladder issues
• Provide vegetable matter regularly
• Never mix tropical and coldwater fish
• Quarantine new fish for 2-4 weeks
• Keep only goldfish with goldfish (usually)