How to take care of goldfish

MD Mustakim Jabir
Read Time 2 Min

Goldfish are one of the most popular pets around the world, and for good reason—they’re beautiful, relatively easy to care for, and can live for many years with proper attention. But don’t be fooled by their simplicity—caring for goldfish requires thoughtful attention to their environment, diet, and health. In this comprehensive guide, I’ll walk you through everything you need to know about goldfish care, using numerical data, peer-reviewed information, and a personal touch.

1. Common vs. Fancy Goldfish: What’s the Difference?

There are two main categories of goldfish: common and fancy. Common goldfish have a streamlined body shape and can grow up to 12 inches in length. They are fast swimmers and more tolerant of environmental changes. Fancy goldfish, on the other hand, have rounder bodies and are often adorned with unique features like bubble eyes or flowing fins. They typically grow to 6–8 inches and require more careful maintenance due to their delicate build.

Did you know? Fancy goldfish varieties like the Oranda and Ranchu have been bred for hundreds of years to develop their unique features.

2. Goldfish Lifespan: How Long Do They Live?

With proper care, a goldfish can live anywhere from 10 to 20 years, though some have been known to live over 30 years. The secret to a long-lived goldfish lies in a proper diet, clean water, and the right tank conditions. Remember, goldfish are not “disposable” pets—they need just as much care as any other!

Fun fact: The oldest recorded goldfish lived for 43 years!

3. Essential Supplies for Goldfish Care

To set up a goldfish tank, here’s what you’ll need:

A spacious tank (more on that next)
A water filter
Dechlorinator (to make tap water safe)
Gravel or sand substrate
Decorations (without sharp edges)
A reliable water test kit
High-quality goldfish food
A net for handling your fish

4. Choosing the Right Tank Size for Goldfish

Goldfish need more space than most people think. For common goldfish, a minimum tank size of 20 gallons is necessary for one fish, with an additional 10 gallons for each additional fish. Fancy goldfish, due to their slower swimming and smaller size, can thrive in a 15-gallon tank, though more space is always better.

Rule of thumb: 1 goldfish per 10 gallons of water.

5. Ideal Water Conditions for Goldfish

Goldfish are cold-water fish, so they thrive in cooler water than tropical species. However, water quality is key to their health. Here’s what you need to maintain:

pH level: 6.5–7.5
Ammonia: 0 ppm (ammonia is toxic)
Nitrite: 0 ppm
Nitrate: below 40 ppm
Weekly water changes of at least 25%

Make sure you use a test kit to monitor these levels regularly.

6. Is a Filter Necessary for Goldfish?

Yes! Goldfish are messy eaters and produce a lot of waste. Without a filter, harmful toxins like ammonia and nitrites can quickly build up in the water. A reliable filter is essential for maintaining good water quality. I recommend a filter with a flow rate of 4–6 times the tank volume per hour.

7. Do Goldfish Need a Heater?

For the most part, no. Goldfish prefer cooler water, around 65–75°F (18–24°C), which is typical of room temperature. However, if your house gets very cold in winter, you may need a heater to ensure the water stays within this range.

8. Optimal Temperature Range for Goldfish

As mentioned above, goldfish thrive in temperatures between 65–75°F. Common goldfish can tolerate lower temperatures down to 50°F, but fancier varieties prefer the warmer end of the spectrum. Sudden changes in temperature can stress your fish, so aim for a stable environment.

9. Decorating Your Goldfish Tank

While you can certainly get creative with tank decorations, remember that goldfish are big, active swimmers. Avoid sharp decorations that can injure their delicate fins, especially in fancy varieties. Opt for smooth rocks, plants (real or fake), and ample swimming space. Goldfish love to explore and will even rearrange objects!

10. What Should You Feed Your Goldfish?

Goldfish are omnivores, so their diet should include a mix of plant-based and protein-rich foods. High-quality goldfish flakes or pellets should be the staple of their diet, supplemented with:

Blanched veggies like spinach or peas
Frozen or live foods like bloodworms or brine shrimp

Feeding variety not only promotes health but also enhances their natural colors.

11. How Often Should You Feed Goldfish?

A common mistake is overfeeding. Goldfish should be fed 2–3 times a day, with only as much food as they can eat in 2 minutes. Overfeeding leads to waste buildup and poor water quality.

12. How to Properly Clean a Goldfish Tank

Regular cleaning is crucial for goldfish health. Here’s a simple routine to follow:

Remove 25–50% of the water weekly and replace it with dechlorinated water.
Use a gravel vacuum to clean the substrate and remove waste.
Gently rinse filter media in tank water (not tap water) to avoid killing beneficial bacteria.
Wipe down glass to remove algae buildup.

Avoid full water changes, as they can shock your fish and disrupt the balance of beneficial bacteria.