🐠Goldfish: gear and buying guides

The goldfish is a social, greedy cyprinid that easily reaches 20 to 30 cm as an adult, a far cry from the fishbowl cliché. It lives in unheated cold water and requires at least 100 L for a single fish, ideally much more since it should be kept in groups. As a heavy waste producer, it calls for oversized filtration and regular water changes.

Profile : 20 to 30 cm as an adult, 100 L minimum per fish, cold water at 18 to 22 °C with no heater.

Species profile

Lifespan

15 to 30 years

Adult size

25 cm

Minimum tank

100 L

Water temperature

18 to 22 °C

pH

7 to 8

Temperament

Gregarious, curious and greedy, it fares poorly alone and needs companions far more than a solitary bowl.

Health watch

dropsy favored by heavily loaded water · swim bladder disorders worsened by overfeeding

🩺 Reminder: this page informs, it does not diagnose. For any symptom or health question, your veterinarian remains the only reference.

Goldfish gear, family by family

• 🍖 Food

  A big-appetite omnivore: sinking cold-water pellets, supplemented with blanched vegetables and frozen foods. Split meals into small portions to limit digestive issues and water pollution.

• 🧴 Care & grooming

  Goldfish produce a lot of waste: plan a filter turning over 4 to 5 times the tank volume per hour and a 20 to 30 percent water change every week. Monitor nitrites and nitrates with regular test kits.

• 🎾 Toys & enrichment

  Choose sturdy plants such as anubias or vallisneria, as goldfish uproot and nibble everything. Smooth driftwood and rounded stones provide exploration areas without damaging their fins.

• 🏠 Bedding & habitat

  Allow 100 L for the first fish and roughly 50 L per additional one, in a tank that is longer than it is tall. Sand or rounded gravel works well, with a lid or hood to limit evaporation.

• 🧳 Travel & safety

  Transport it in a bag filled one-third with water and two-thirds with air, secured in an insulated cooler. Then acclimate for 20 to 30 minutes to equalize temperature before releasing it without the bag water.

• 🧰 Accessories

  A powerful external filter, a wide net and a gravel vacuum are essential; a heater is unnecessary. Expect an initial equipment budget of around 150 to 300 euros for a 100 to 200 L tank.

Guides to read

• Community aquarium or species-only tank: which is right for a first setup?Bedding & habitat

  Community aquarium or species-only tank: pros, cohabitation risks and advice for choosing how to set up your first aquarium.

• Best easy aquarium plants without CO2 for beginnersToys & enrichment

  Which aquarium plants can you choose without CO2 injection? A selection of hardy, easy plants for a beginner's planted tank.

• Budget for a first brackish water aquarium: the real cost to get startedBedding & habitat

  How much does a first brackish water aquarium cost? Tank, filtration, salt and salinity monitoring, budgeted item by item.

• Changing filter media too often: the mistake that wrecks your aquarium's cycleCare & grooming

  Why you should never replace all your filter media at once: nitrifying bacteria, replacement frequency and the right habits.

• Restarting a neglected aquarium: a step-by-step guideCare & grooming

  How do you restart an aquarium that's been left neglected without endangering the fish? Steps, water changes and mistakes to avoid.

• GH, KH and pH: understanding and adjusting aquarium water hardnessCare & grooming

  GH, KH, pH: what do these three readings actually measure, and how do you adjust aquarium water hardness without stressing the fish?

• Upgrading to a bigger aquarium: moving your fish without the stressBedding & habitat

  How do you upgrade to a bigger aquarium without breaking the biological cycle or stressing your fish? Steps and mistakes to avoid.

• Aquarium electrical safety: GFCI protection and good habitsTravel & safety

  Heater, filter, lighting near the water: what electrical precautions keep an aquarium safe for fish and people?