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A Simple Guide to Goldfish Care

Goldfish are one of the most misunderstood aquatic pets in the hobby. Often seen as “starter fish,” they’re actually intelligent, long-lived animals capable of growing large and forming surprising little personalities of their own. With the right care, a goldfish can live 10–20 years or more, becoming a true companion rather than a temporary decoration. This guide will walk you through the essentials: housing, feeding, compatibility, behaviour, and everything new owners need to know to keep their goldfish thriving.

Housing: The Most Important Part

Despite their reputation, goldfish are not small-tank fish. They’re messy, fast-growing, and need plenty of space to swim. A bowl is never suitable, it leads to stunted growth, poor water quality, and a drastically shortened lifespan.

Tank size recommendations:

  • Single fancy goldfish: Minimum 75 litres
  • Each additional fancy: +40–50 litres
  • Single common/comet goldfish: 150–200 litres
  • Each additional common/comet: +75–100 litres
    (Common and comet goldfish belong in ponds long-term due to their size and speed.)

Goldfish also need high-quality filtration. A filter rated for at least twice your tank size helps manage their waste and keeps the water clean. Smooth substrate like sand is ideal, and decorations should have no sharp edges since goldfish can injure themselves easily.

Water Quality & Maintenance

Goldfish thrive in stable, well-cycled aquariums. Before adding fish, the tank should be fully cycled to establish beneficial bacteria that convert toxic ammonia into safer forms.

Key water parameters:

  • Ammonia: 0
  • Nitrite: 0
  • Nitrate: Ideally under 20–40 ppm
  • Temperature: 18–23°C for fancies; commons tolerate cooler
  • pH: Stable between 7.0–8.4

Perform weekly water changes (25–50%) depending on tank size and stock level. Regular testing is essential — goldfish love to keep you humble.

Feeding: Variety = Healthier Fish

Goldfish are omnivores that need a varied diet to prevent digestive issues and promote good colour and growth.

Offer:

  • High-quality sinking goldfish pellets
  • Blanched veggies (peas, spinach, zucchini)
  • Frozen foods like bloodworms or brine shrimp (as treats)
  • Occasional gel foods for added nutrition

Avoid flakes, they often cause buoyancy issues and poor nutrition. Feed small portions once or twice a day, only what they can consume in under a minute.

Compatibility: Choose Tank Mates Carefully

Goldfish are peaceful, but their care needs limit their compatible tank mates.

Great tank mates:

  • Other fancy goldfish (keep fancies with fancies due to speed difference)
  • White cloud mountain minnows (for large setups)
  • Some species of cold-water snails

Avoid:

  • Tropical fish (temperature mismatch)
  • Fast, nippy species like barbs
  • Shrimp (goldfish usually snack on them)
  • Commons + fancies together (commons outcompete fancies easily)

Goldfish also do best in small groups—their social behaviour shines when kept with friends.

Behaviour, Lifespan & Personality

Goldfish are surprisingly intelligent. They recognise their humans, beg for food like wet puppies, and can even learn simple tricks. With proper care, many live well over 15 years, and some have reached 40+.

Signs of a happy goldfish:

  • Active swimming
  • Healthy appetite
  • Smooth, even scales
  • Clear eyes
  • Curious behaviour

Signs something’s wrong:

  • Clamped fins
  • Sitting at the bottom
  • Gasping at the surface
  • Floating oddly (could be swim bladder issues)
  • Red streaks in fins
  • Rapid breathing

Prompt water testing is your first step with any problem.

Enrichment & Environment

Goldfish are playful and benefit from enrichment. Offer:

  • Live plants like anubias or hornwort (choose sturdy species)
  • Smooth rocks and caves
  • Bubblers or air stones
  • Occasional rearranging to stimulate exploration

A happy goldfish is an active, curious goldfish.

Goldfish Shopping List

(Everything You Need for a Healthy, Happy Goldfish Tank)**

Goldfish may look simple, but they’re big, messy, long-lived “little aliens” who need proper space, strong filtration, and a well-planned setup. This shopping list keeps everything beginner-safe and easy to follow.

Tank & Habitat Essentials

Tank Size

Choose based on the type of goldfish:

  • Fancy goldfish:
    • 75 litres for the first
    • +40–50 litres for each additional
  • Common/comet goldfish:
    • 150–200 litres for the first
    • +75–100 litres for each additional
      (Ideally suited for ponds long-term)

Equipment & Decor

  • High-quality aquarium (with lid optional)
  • Powerful filter rated for 2× the tank volume
  • Aquarium-safe heater (optional for fancies)
  • Air pump + airstone (excellent for high oxygen needs)
  • Fine sand or smooth gravel (avoid sharp substrates)
  • Aquarium-safe rocks or driftwood
  • Smooth-edged decorations (no sharp points—goldfish bump into everything)
  • Live plants (anubias, hornwort, vallisneria) or silk plants

Water Care & Maintenance Supplies

Goldfish produce a lot of waste, so good water maintenance is non-negotiable.

  • Liquid test kit (ammonia, nitrite, nitrate, pH)
  • Water conditioner (dechlorinator)
  • Siphon/gravel vacuum
  • Dedicated water-change bucket
  • Filter media (sponges, ceramic rings—avoid carbon unless needed)
  • Aquarium thermometer
  • Aquarium-safe algae scraper
  • Aquarium salt (for mild stress treatment—not everyday use)

Food & Nutrition

Variety is key for healthy digestion, bright colours, and proper growth.

Staple Foods

  • High-quality sinking goldfish pellets (avoid cheap fillers)
  • Gel food mixes (excellent nutrition, great for fancy varieties)

Fresh Veggies

  • Blanched peas (de-shelled)
  • Spinach
  • Zucchini
  • Lettuce (romaine)

Treats

  • Frozen bloodworms
  • Frozen brine shrimp
  • Daphnia

Avoid flakes, they’re outdated, messy, and contribute to swim bladder issues.

Optional but Highly Recommended

  • Backup sponge filter (great for emergencies)
  • Battery-powered air pump (for power outages)
  • Extra filter sponges
  • Plant fertilizer (fish-safe, if keeping live plants)
  • Aquarium background (calms fish, reduces stress)
  • Digital feeding timer (helpful for consistent routines)

Health & Emergency Kit

Goldfish are hardy when kept properly, but quick access to the basics helps:

  • Quarantine tub or spare tank
  • Spare air pump + airstone
  • Indian almond leaves (gentle antibacterial properties)
  • Epsom salt (for mild constipation or buoyancy issues—use correctly)
  • Medications safe for scaleless species (only if needed)

Quick Starter Bundle (Beginner-Friendly)

For someone starting fresh, here’s the simplified but still ethical list:

  • 75L+ tank (fancy goldfish) or 150L+ (common/comet)
  • Strong filter (2× turnover)
  • Water test kit
  • Dechlorinator
  • Sand or smooth gravel
  • 2–3 sturdy plants
  • Airstone + air pump
  • Siphon + bucket
  • Sinking pellets
  • Gel food
  • Thermometer
  • Smooth décor

Final Thoughts

Goldfish aren’t low-effort pets, they’re rewarding, social creatures that thrive with proper space, clean water, and a nutritious diet. When cared for properly, your little alien can become a bright, lively centrepiece in your home for many years. With patience, good husbandry, and a bit of underwater love, your goldfish will repay you with their goofy charm and big aquatic personalities.