1. Select your tank. A common mistake is putting goldfish in so-called “goldfish bowls,” but bowls simply are not big enough to let a goldfish thrive. For fancy goldfish, aim for 10(at the bare minimum)/15/20 gallons for the first fish, and 10 gallons for each additional fish. For comet goldfish, aim for 55 gallons for the first fish, and 20 for each additional fish.

2. Select the filtration. Goldfish are messy fish with large bioloads, so a good filter is necessary. There are many types of filtration, but to keep it simple, the better types are the “Bio-wheel” filters that hang on the side of the tank. Under gravel filters are only recommended if you have a strict budget or you are housing sensitive goldfish such as bubble eyes. Canister filters are for large tanks, as they are a more powerful version of the “bio-wheel” filters. You want to provide double the filtration for the tank, so for example, if you have a 20 gallon tank, get a filter rated for 40 gallons or two filters rated for 20 gallons.

3. Decide on heating systems. Heating for cold water tanks isn’t as much of an issue as it is for tropical fish. In fact, you can keep a goldfish tank without a heater. The temperature should be between 60 degrees Fahrenheit and 72 degrees F, warmer water may harm your fish.

4. Put your fish tank together, and install the filter, but don’t plug it in. Set your heater up (if you have one) but DON’T plug it in.

5. Put in your gravel and decorations.

6. Fill your tank with water treated with water conditioner. At this stage you can add any live plants you have.

7. Start up your filter according to the directions it came with.

8. Let your setup run for a few days to ensure that all your equipment is running properly.

9. Cycle your tank. This step is important to the health of your fish. You can add fish food and let it decompose in your aquarium which wil bring ammonia into the water and cause beneficial bacteria to grow.

10. Test the water. Once your water tests 0 for ammonia and nitrite, and has some nitrate, you can add your goldfish.

11. Add your goldfish slowly. Don’t dump a bunch of goldfish all at once into your tank, as this might cause stress to your biological system. Only add one or two fish at a time, with several weeks between each group. Congratulations, your fish tank should look great!

12. Keep doing weekly 50-75% water changes to keep up with the massive amount of waste goldfish produce.