13 Things to Know Before Getting a Goldfish
You clicked because goldfish look easy. Weve kept them for years, and we promise: a little prep makes all the difference.
Heres what actually matters so your fish thrives, not just survives.
Quick, clear, and no fluff.
1. A Bowl Is Not Big Enough
Goldfish are high-waste fish that grow large. A bowl traps ammonia and starves them of oxygen.
Start with at least 20 gallons for the first fancy goldfish, plus 10-15 gallons for each additional. Commons/comets/shubunkins need much more or a pond.
2. Filtration Is Non-Negotiable
Goldfish constantly stir up debris and produce plenty of waste. You want robust mechanical and biological filtration.
Choose a filter rated for at least double your tank volume and keep flow gentle for fancies with heavy fins.
Mechanical
Sponges/floss trap particles so water stays clear.
Biological
Porous media hosts bacteria that convert toxic ammonia to safer nitrate.
3. You Must Cycle the Tank First
Cycling grows beneficial bacteria that convert ammonia to nitrite and then nitrate.
Use an ammonia source (fishless is kinder), test daily, and wait until ammonia and nitrite read zero and nitrate is present before adding fish.
4. They Can Live a Very Long Time
With proper care, goldfish commonly reach the teens, and some live into their twenties. The tiny feeder fish image is misleading.
Plan like you would for a small dog: space, consistent care, and backup for vacations.
5. Commons vs. Fancies Need Different Space
Common, comet, and shubunkin goldfish are streamlined, fast swimmers that thrive in large tanks or outdoor ponds.
Fancy varieties (oranda, ranchu, ryukin, telescope) are slower, bulkier, and better in spacious indoor aquariums without strong currents.
Setup right and feeding gets much easier
6. Overfeeding Is the Fastest Way to Trouble
Goldfish act hungry. Dont buy it. Feed small portions 1-2 times daily they finish in under a minute, then stop.
Rotate a quality sinking pellet with blanched veggies (peas with skins removed, spinach) and occasional frozen foods. Sinking foods reduce gulping air and buoyancy issues.
7. Tap Water Needs Conditioner
Most tap water contains chlorine or chloramine that harm gill tissue and your biofilter.
Use a conditioner that treats both, every time you add new water.
8. Choose Safe Substrate and Decor
Goldfish sift constantly. Fine sand or bare-bottom tanks are easiest to clean and safest.
If you prefer gravel, pick pieces too large to fit in a mouth to avoid choking or impaction. Avoid sharp decor that can tear fins or eye stalks.
They will nibble tender leaves, but hardy plants like anubias, java fern, and hornwort often do fine if securely attached.
Snails help with leftovers but add to the bioload. You still need water changes and a filter.
9. Room-Temperature, Not Tropical
Goldfish are cold-water tolerant and do well around 65-748F.
Avoid sudden swings. Heaters arent mandatory in a stable room, but in winter a low-watt heater can prevent dips for delicate fancies.
10. Tankmates: Be Picky
Goldfish will eat anything that fits in their mouth and are clumsy swimmers.
Best companions are other goldfish of similar type and size. Avoid fin-nippers and tiny fish. If you try snails or large, peaceful species, monitor closely.
Pros
Whats to love
- Easygoing personalities
- Interactive and fun to hand-feed
- Hardy once established
Cons
Real challenges
- High waste means big filters and water changes
- Can uproot plants and redecorate daily
- Fancies are prone to buoyancy and eye injuries
11. Weekly Maintenance Is Simple and Essential
Plan on 25-50 percent water changes weekly, vacuuming debris from the substrate.
Rinse filter media in removed tank water, not tap, to preserve bacteria. Test ammonia, nitrite, nitrate, and pH regularly.
12. Where You Buy Matters
Healthy stock saves money and heartbreak. Look for clear eyes, smooth scales, level swimming, and active foraging.
Quarantine new fish for 2-4 weeks before adding to your display to prevent parasites from wiping out your tank.
13. Budget for the Setup, Not Just the Fish
The fish is cheap; the environment isnt. Youll need a proper tank, lid, stand, strong filter, test kit, conditioner, and food.
Annual Cost Breakdown
| Expense | Annual Cost |
|---|---|
| One-time setup (20–40 gal tank, lid, stand, filter, gravel/sand, decor) | $200–$500+ |
| Water conditioner and test kit (annual) | $30–$60 |
| Food and veggies (annual) | $40–$100 |
| Replacement media/parts (annual) | $20–$60 |
| Est. Annual Total | $290–$720+ first year, then $90–$220 annually |
One fancy goldfish is comfortable in 20 gallons. Add 10–15 gallons for each additional fancy. Commons/comets outgrow a 20 fast and need much larger tanks or a pond.
Likely low oxygen or high ammonia. Increase aeration, test water immediately, and perform a partial water change with conditioned water.
They need a day/night cycle. Room light can work, but an aquarium light on a timer (8–10 hours) helps you enjoy the tank and supports plants.
Generally not ideal. Goldfish prefer cooler water, are messy, and may eat smaller fish. Stick to other goldfish for the best match.
