How to Keep Goldfish

Your goldfish would be happiest with another goldfish.

Your goldfish would be happiest with another goldfish.

Before rushing home with a cute little finned pet in a plastic bag, bear in mind two things. Goldfish get big -- at least 8 inches in some cases -- and they are hardy, but not that hardy. Unless you want a dead fish, don’t pop Goldie in a bowl and forget about him.

Items you will need

  • 25-gallon or larger cold water tank with gravel, filter, light and aquatic plants
  • Nitrifying bacterial culture
  • Goldfish flake food
  • Live food
  • Gravel cleaner
  • Buckets
  • Nitrate, nitrate and pH test kits
  • Goldfish care manual

Step 1

Set up the tank at least a week before you acquire your goldfish. Aquatic ecosystems have a delicate balance and the microorganisms that they depend upon must become established before you add higher organisms. Setting up a tank goes like this: add physical items (gravel, rocks, filter), add water (which at this stage does not need to be dechlorinated since the chlorine will evaporate anyway), wait a few days, add plants and a nitrifying bacteria starter solution, wait a few more days, add a couple of aquarium snails, wait a few more days, check the pH and add one or two fish, wait a couple of weeks and add another fish or two, as goldfish prefer living in small groups.

Step 2

Feed your goldfish dry food at least three times a day. Feed no more dry food than he -- or they -- can eat within a couple of minutes. Goldfish need small, frequent meals, not one or two big ones. Supplement with occasional live food, such as daphnia, brine shrimp or bloodworms, which allows natural behaviour and provides extra nutrients.

Step 3

Perform partial water changes once a week. Remove about a quarter of the water using a gravel cleaner with tube and a bucket. Remove any debris in the tank along with the water. Top up the tank slowly with fresh, dechlorinated water.

Step 4

Monitor nitrate and nitrite levels in the tank, which should be close to zero. Test weekly or monthly. Nitrite, which forms from nitrates, is toxic. If there is any in the tank, perform an immediate partial water change and thereafter increase the frequency of your water changes. Nitrate itself is not so toxic but detectable levels also indicate there is too much waste.


  • Dechlorinate water either by leaving tap water in buckets for 24 hours or using a dechlorinator from an aquarium supply store as per the instructions.
  • A 25-gallon tank is big enough for just one goldfish. If you want a small group, which is preferable, you’ll need a 50-gallon or larger tank.


  • Note that this article is intended to provide an idea of the care and equipment goldfish need. It is not intended to be a complete guide. Buy a book on goldfish care for comprehensive details.
  • Fish are sensitive to any changes in their environment. Position the tank out of direct sunlight and away from heaters to avoid temperature fluctuations. For the same reason, when cleaning the tank, add fresh water gradually, not all at once, because if it is colder than the water in the tank, doing so will shock the fish.

About the Author

Judith Willson has been writing since 2009, specializing in environmental and scientific topics. She has written content for school websites and worked for a Glasgow newspaper. Willson has a Master of Arts in English from the University of Aberdeen, Scotland.

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