Can two goldfish live in a 5 gallon?

The short answer is yes, two common goldfish can live in a 5 gallon tank. However, there are some important factors to consider to ensure the fish stay healthy and happy.

Tank Size Recommendations for Goldfish

Most experts recommend a minimum of 20 gallons for the first goldfish, plus an additional 10-20 gallons per additional goldfish. This is because goldfish are fairly large fish that produce a lot of waste. They need adequate space and powerful filtration to stay healthy.

While a 5 gallon tank is below the recommended minimum, it can work for two small to medium goldfish. The key is to choose fish that will stay under 3 inches, perform frequent water changes, and provide strong filtration.

Choosing the Right Goldfish for a 5 Gallon Tank

Fancy goldfish varieties tend to stay smaller than common goldfish. Some good options for a 5 gallon tank include:

  • Fantail
  • Ryukin
  • Pearlscale
  • Ranchu

Avoid comet, shubunkin, and common goldfish as they can reach 12 inches or more at full size. Also avoid plecostomus and other bottom feeders that require more space.

Select young, juvenile goldfish that are under 2 inches long. This allows room for some growth in the 5 gallon tank before an upgrade is needed.

Caring for Goldfish in a Small Tank

Caring for two fancy goldfish in a 5 gallon tank takes some special considerations:

  • Filtration – Use a high quality filter rated for at least twice the tank size. Canister filters or HOB filters designed for 10+ gallon tanks help remove waste.
  • Aeration – Proper oxygenation is essential. Use an air stone or air driven sponge filter.
  • Weekly water changes – Change out 25-50% of the water weekly to dilute nitrates. Use a gravel vacuum.
  • Test water quality – Check ammonia, nitrite, nitrate levels weekly with a test kit. Keep nitrates under 40 ppm.
  • Plants – Add live plants like anubias or java fern to help absorb some waste.

With close monitoring and the right equipment, a 5 gallon tank can support two small fancy goldfish for about one year. After that, an upgrade to a larger tank is recommended.

Setting Up the 5 Gallon Tank

Follow these steps to properly set up a 5 gallon tank for two goldfish:

  1. Place the tank on a sturdy stand away from direct sunlight.
  2. Add a high quality filter designed for a 10+ gallon tank.
  3. Add a substrate like fine gravel or sand, 1-1.5 inches deep.
  4. Decorate with smooth rocks and driftwood arranged to allow swimming space.
  5. Fill the tank with dechlorinated water to the proper level.
  6. Install a heater and thermometer to keep water at 72-78°F.
  7. Add live plants if desired.
  8. Let the tank cycle for 2-6 weeks before adding fish.
  9. Test water parameters and do water changes as needed.
  10. Acclimate and add two small fancy goldfish.

Cycling the tank allows beneficial bacteria to establish and convert ammonia and nitrite to less toxic nitrate. This makes the water safe for fish long-term.

Goldfish Diet and Feeding

Goldfish are omnivores that require a varied diet. Feed a quality flake or pellet food designed for goldfish 1-2 times per day. Offer only an amount fish can eat within 2 minutes.

Supplement with treats like:

  • Blanched vegetables – peas, zucchini
  • Brine shrimp
  • Daphnia
  • Bloodworms
  • Sinking algae wafers

Avoid overfeeding, which fouls the water. Remove uneaten food promptly.

Signs of Stress in a Small Tank

Watch for these signs of stress indicating the 5 gallon tank is too small:

  • Bottom sitting
  • Rapid gilling
  • Swimming only at top
  • Loss of appetite
  • Rubbing against objects

Act promptly if stress signs appear. Try more frequent water changes first. If that doesn’t help, upgrade to a larger tank.

When to Upgrade the Tank

Plan to upgrade goldfish to a larger tank within 6-12 months. Some signs it’s time for an upgrade include:

  • Fish reaching over 2 inches in length
  • Water quality issues between changes
  • Signs of stress or aggression
  • Trouble maintaining stable water parameters

Goldfish growth depends partly on tank size. A 5 gallon tank can stunt growth somewhat, but an upgrade should still take place within a year.

How Big of a Tank Do Goldfish Need?

Here are general goldfish tank size guidelines:

Number of Fancy Goldfish Minimum Tank Size
1 20 gallons
2 30 gallons
3 40 gallons
4 55 gallons
5 70 gallons

For common goldfish that reach 12+ inches, allow 12-20 gallons per fish. Very large tanks or ponds are ideal.

Tank Setup Tips for Goldfish

Follow these goldfish tank setup tips for a healthy habitat:

  • Give 1-2 gallons per inch of fish.
  • Select wide rectangular tanks as goldfish are fast swimmers.
  • Use smooth substrate for bottom dwelling fish.
  • Include hiding spots and anchored plants.
  • Maintain water temperature between 65-75°F.
  • Equip with strong external canister filter rated for 2-3x total gallons.
  • Position tank away from direct sunlight and high traffic areas.

FAQ on Goldfish Tank Size

Can I keep goldfish in a 5 gallon tank permanently?

No, a 5 gallon tank is not suitable for goldfish permanently once they reach adult size. Fancy varieties may be kept temporarily in a 5 gallon tank for the first 6-12 months if care guidelines are followed. But they will soon need an upgrade to a 20-30 gallon tank minimum.

What fish can live with goldfish in a 5 gallon?

No other fish are recommended with two fancy goldfish in a 5 gallon tank. The bioload is already heavy. Other small community fish also prefer warmer water than goldfish, so are not compatible.

Can a 10 gallon tank hold 2 goldfish?

A 10 gallon tank can hold two fancy goldfish juveniles a bit longer, but still requires diligent care and maintenance. Shoot to upgrade to 20+ gallons within their first year to prevent stunting growth and issues with water quality.

How many years do goldfish live in a 5 gallon tank?

In ideal conditions with perfect water quality, goldfish can survive several years in a 5 gallon tank. But they are likely to suffer stunted growth, be prone to disease, and have a severely shortened life span. Shoot for at least 1-2 years in a proper sized tank for a healthy life expectancy.


While not ideal, two small fancy goldfish can live in a 5 gallon tank temporarily. Select fish that stay under 3 inches, follow care guidelines closely, and plan to upgrade within 6-12 months. With diligent tank maintenance and careful fish selection, a small tank can work short term.

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