The supplies you need for a goldfish tank are a properly sized aquarium, a strong filter, a heater (in most cases), a water conditioner, a test kit, substrate, and basic maintenance tools. That's the core list. Goldfish are sold with a reputation for being beginner fish, but they're actually more demanding than most tropical fish for waste production and space requirements, which means cutting corners on equipment usually results in sick or dead fish within months.

This guide walks through each category of supplies, which specific products work well, what to skip, and the numbers that matter so you can set up a tank that keeps goldfish alive for their full 10-20 year lifespan.

The Right Tank Size

Goldfish size is the first place beginners go wrong. The old "1 inch of fish per gallon" rule doesn't work for goldfish. A 6-inch fancy goldfish producing the waste of a 6-inch fish in a 6-gallon tank will crash water quality in hours.

The working guidelines used by most experienced goldfish keepers are: - Fancy goldfish (orandas, ryukins, black moors): 20 gallons for the first fish, 10 gallons per additional fish - Slim-bodied goldfish (comets, shubunkins, common): 40 gallons for the first fish, 20 gallons per additional fish

For fancy goldfish, a 40-gallon breeder tank is a great starting point for 2 fish. It's wide enough for the fish to turn comfortably and has enough water volume to buffer water quality swings. The Aqueon 40-gallon breeder (36 x 18 x 17 inches) is a popular choice and often available in starter kits.

Bowls and tanks under 10 gallons are not suitable for any goldfish under any circumstances. The surface area is too small for gas exchange, filtration is inadequate, and temperature swings are extreme.

Filtration: The Most Important Piece of Equipment

Goldfish produce roughly 3-4 times the waste of a similarly sized tropical fish. Your filter needs to handle that load. The standard recommendation is to run filtration rated for 4-5 times your tank volume per hour.

For a 40-gallon goldfish tank, you want a filter turning over at least 160-200 gallons per hour, and ideally 200-300 GPH for a heavy goldfish load.

Hang-on-Back Filters

The AquaClear 70 (rated for 70 gallons, 300 GPH) is one of the most reliable HOB filters available. It uses a three-stage filtration system with foam insert, activated carbon, and BioMax ceramic rings. The foam and BioMax are where beneficial bacteria colonize, so you keep those long-term. Replace only the carbon every 4-6 weeks.

The Seachem Tidal 55 and Tidal 75 are newer designs with surface skimming capability, a feature that's genuinely useful for goldfish since they produce oils that create surface film. The Tidal 75 runs about $75-85 and handles up to 75-gallon tanks at 350 GPH.

Canister Filters

For tanks over 55 gallons or four or more goldfish, a canister filter is worth the upgrade. The Fluval 307 handles 70-gallon tanks and provides more biological media volume than any comparably priced HOB. The Eheim Classic 350 has been a standard recommendation for 20+ years because it rarely fails and runs silently. Canister filters require maintenance every 4-8 weeks (cleaning media under tank water, not tap water) but provide superior biological filtration.

Water Conditioning and Testing Supplies

Before you add any fish, the tank water needs to be dechlorinated and the nitrogen cycle needs to be established.

Water Conditioner

Seachem Prime is the industry standard at this point. It dechlorinates, detoxifies chloramines (not just chlorine), and temporarily neutralizes ammonia and nitrite at a dose of 5 mL per 50 gallons. The 500 mL bottle costs about $12-14 and treats around 5,000 gallons, making it significantly cheaper per treatment than API Stress Coat or Tetra AquaSafe.

Use it every water change and any time you're treating sick fish or dealing with elevated ammonia.

Test Kit

A liquid test kit is more accurate than test strips and costs less per test. The API Freshwater Master Test Kit includes tests for ammonia, nitrite, nitrate, and pH. It runs about $25-30 and includes enough reagent for 800 tests. You need to test weekly during the nitrogen cycle (takes 4-6 weeks) and monthly once the tank is established.

Target parameters for goldfish: - Ammonia: 0 ppm - Nitrite: 0 ppm - Nitrate: under 20 ppm (do a water change when it hits 20-40) - pH: 7.0-7.4

Cycling Supplements

Seachem Stability or API Quick Start can speed up the initial nitrogen cycle by seeding the tank with beneficial bacteria. These aren't magic, but they can reduce the cycle time from 4-6 weeks to 2-3 weeks. Add a double dose when starting and a maintenance dose with each water change for the first month.

Substrate Options

Goldfish are diggers. They root through substrate constantly, which can stir up debris and make maintenance harder. Your substrate choice affects both aesthetics and cleanup difficulty.

Bare Bottom

A bare bottom tank is the easiest to clean and allows you to see every piece of waste. Many goldfish breeders use bare bottom tanks specifically for this reason. The downside is it looks sterile and provides less surface area for beneficial bacteria.

Sand

Pool filter sand (Fairmount Minerals or similar, about $8-10 for a 50-lb bag at a pool supply store) is a popular choice. It's inert, doesn't affect pH, and settles quickly after being disturbed. Goldfish like to root through it. Use a 1-2 inch layer. Avoid play sand, which can have additives.

Large Gravel or River Rocks

Avoid fine gravel with goldfish. They swallow it, and it can cause intestinal impaction. If you use gravel, choose pieces larger than 1/2 inch diameter so they physically cannot ingest them. The CaribSea Eco-Complete and Spectrastone Premium Gravel both come in sizes that work. Decorative large river pebbles from a garden center are inexpensive and work well.

Heating and Temperature

Fancy goldfish are comfortable between 65-72°F. Slim-bodied goldfish can handle temperatures down to 50°F but are most active between 65-75°F. If your home stays above 65°F year-round, you don't technically need a heater for fancy goldfish, but most homes have overnight temperatures that drop below this in winter.

A 150-watt heater is appropriate for a 40-55 gallon tank. The Eheim Jager TruTemp is calibrated precisely and adjustable in 0.5°F increments. The Fluval E200 has a digital display that shows actual water temperature versus target temperature, which is useful for monitoring.

Keep a separate thermometer (the Zoo Med TH-22 digital stick-on style or the Marina Floating Thermometer) to verify your heater isn't drifting.

Lighting

Goldfish don't have specific lighting needs, but lights improve visibility of the fish and can support plant growth. The NICREW ClassicLED Plus and the Fluval Plant 3.0 are popular choices. For a basic fish-only tank, any LED fixture rated for your tank length will work.

Aim for 8-10 hours of light per day using an outlet timer. Consistent photoperiods reduce algae overgrowth and help maintain your fish's biological rhythms.

Maintenance Tools

You'll use these every week:

  • Gravel vacuum/siphon: The Python No-Spill Clean and Fill system connects to a faucet and removes waste while draining and refills automatically. It costs $35-60 depending on the length but eliminates carrying buckets. For small tanks, the Eheim Quick Vac Pro battery siphon costs about $30 and is fast for spot cleaning.
  • Magnetic algae scraper: The Fluval Edge Curved Scraper or Tunze Care Magnet work well. For thick algae buildup, the Mag-Float glass cleaner with a stainless scraper blade on one side cuts through it without scratching acrylic or glass.
  • Bucket: Keep a dedicated 5-gallon bucket for aquarium use only. Home Depot orange buckets work fine. Label it "AQUARIUM ONLY" so nobody uses it with cleaning products.
  • Sponge or filter brush: For cleaning filter intake tubes. Fluval sells a kit with multiple brush sizes for about $8.

Decorations and Tank Enrichment

Goldfish benefit from environmental enrichment. They're intelligent fish that learn to recognize their owners and get bored in empty tanks.

Avoid decorations with sharp edges since goldfish fins are delicate and tear easily. The plastic plants from brands like Marina tend to have hard plastic points. Silk plants (Penn-Plax makes good ones) are safer. Live plants are even better, but stick to hardy species like anubias, java fern, or hornwort since goldfish eat most softer plants.

Caves and hiding spots reduce stress. A simple piece of slate or a smooth ceramic pot on its side works. For a clean look, smooth river stones arranged in a small arch cost almost nothing and give the fish a place to shelter.

You can see full breakdowns of how these supplies fit into complete setups in our guide to Best Aquarium Equipment for different budgets and tank sizes.

FAQ

Do goldfish need an air pump if they have a filter?

Not always. A hang-on-back filter with good surface agitation often provides adequate oxygenation. But goldfish are heavy oxygen consumers, and adding an airstone with a Tetra Whisper 20 or 40 pump provides a meaningful safety margin, especially in warmer months or overstocked tanks. It costs about $10-15 and is worth it.

How often do you change water in a goldfish tank?

With a properly sized, filtered tank, a 25-30% water change once a week maintains good water quality. Overstocked tanks or heavily fed fish may need 30-50% changes twice weekly. Test your nitrate level to calibrate. When nitrate hits 20-40 ppm, it's time for a change.

Can goldfish live with tropical fish?

In most cases, no. Goldfish prefer cooler water (65-72°F) than most tropical fish (76-82°F). There are some temperature-tolerant fish like white cloud mountain minnows and rosy barbs that coexist well with goldfish, but adding a heater for tropical fish usually stresses goldfish, and keeping the tank cool stresses the tropicals.

What's the minimum tank size for one fancy goldfish?

Twenty gallons is the widely accepted minimum for one fancy goldfish, but 30 gallons gives you more buffer for water quality and lets the fish express normal behavior. A 10-gallon tank will keep a small fancy goldfish alive temporarily, but the fish will be stunted and stressed over time.