How to Set Up a Goldfish Tank: Step-by-Step Guide

Goldfish are not bowl fish. They grow large, make a lot of waste, and live for many years. A good setup is the best way to keep them healthy. Here is a simple plan for setting up a tank for fancy goldfish like Ranchu, Oranda, and Lionchu.

Step 1: Pick the Right Tank Size

• First fancy goldfish: at least 20 gallons
• Each extra fish: add 10 to 15 gallons

A wider tank is better than a tall one because it gives more surface area for oxygen.

Step 2: Choose a Strong Filter

Goldfish waste is heavy, so use a filter rated for a tank larger than yours. For gentle swimmers like Ranchu and Lionchu, pick a filter with adjustable flow or use a sponge filter. Add an air stone for extra oxygen. See our aquarium filters.

Step 3: Choose a Substrate

• Bare bottom: easiest to clean
• Smooth sand: looks natural and is safe for bellies
• Avoid small gravel. Goldfish can swallow it.

Step 4: Add Safe Decor

Use smooth decor only. Sharp edges can tear fins and wen. Hardy plants like anubias and java fern work well. Most other plants get eaten.

Step 5: Add Water and Dechlorinator

Fill the tank and add a dechlorinator that removes both chlorine and chloramine.

Step 6: Cycle the Tank

Do not add fish yet. A tank needs beneficial bacteria to handle waste. This usually takes 4 to 6 weeks. Follow our guide on how to cycle a fish tank.

Step 7: Set the Temperature

Fancy goldfish do well at 68 to 75°F long term. A small heater helps keep things steady if your room changes a lot. New fish from Thailand may need warmer water at first. See our acclimation guide.

Step 8: Add Fish Slowly

Add only a few fish at a time and quarantine new fish first. See how to set up a quarantine tank.

Step 9: Build a Care Routine

• Daily: feed small amounts and watch your fish
• Weekly: test water and change 25 to 50 percent. See our water change guide.
• Monthly: check equipment and rinse filter media in old tank water

Goldfish Tank Shopping List

• Tank and lid
• Filter and air pump with air stone
• Dechlorinator
• Liquid test kit
• Siphon for water changes
• Smooth decor and hardy plants
• Sinking pellets

Frequently Asked Questions

Do goldfish need a heater?

Not always, but it keeps the temperature steady.

Can I use tap water?

Yes, if you add a dechlorinator.

How long before I can add goldfish?

After your tank is fully cycled, usually 4 to 6 weeks.

Do goldfish need light?

A simple light on a regular schedule of 8 to 10 hours helps them show color. Avoid direct sun, which causes algae.

Ready for Your Fish?

Once your tank is ready, browse our Ranchu, Lionchu, and Oranda goldfish.