Goldfish (Carassius auratus) are among the most beloved freshwater aquarium fish worldwide, admired for their vibrant colors, engaging behaviors, and relative ease of care. Whether you’re a seasoned aquarist or a beginner looking to start your aquatic journey, understanding the basics of goldfish care is essential for maintaining healthy and thriving pets.
Goldfish Origins and History
Goldfish (Carassius auratus) have been kept as pets for over 1,000 years. Their story begins in ancient China around 960 AD, where people first started keeping them for their beauty.
Goldfish come from a type of wild fish called the Prussian carp (also known as Gibel carp), which is usually grey in color. But over time, some fish showed golden or orange coloring. The Chinese noticed this and began selectively breeding them to make those colors stronger.
Later, the Japanese also started breeding goldfish and developed many new fancy goldfish types with fancy tails, unique shapes, and brighter colors, such as Orandas, Ranchus, and Ryukins.
Thanks to hundreds of years of careful breeding, goldfish have changed a lot. They’ve gone from plain, grey fish in the wild to the colorful and sometimes unusual-looking pets we see today — with long fins, bubble eyes, and a wide range of colors.
Today, goldfish are one of the most popular pet fish in the world, loved by aquarium hobbyists and families alike.
Understanding Goldfish Varieties or Types
There are over 100 different types of goldfish in the world today. Some of these unique varieties are only found in Asian countries, and not easily available in Europe or America.
If you’re new to keeping goldfish, it’s best to start with hardy and affordable types like Comets, Fantails, Orandas, Ranchus, and Black Moors. These goldfish are easier to care for and more forgiving for beginners.
Once you gain more experience, you can explore fancy goldfish varieties such as Bubble Eye, Lionhead, and Celestial Eye goldfish. These exotic types are more delicate and require special care, but they’re stunning to look at.
Goldfish Colors: What Colors Can Goldfish Be?
Goldfish come in many beautiful colors — but surprisingly, they are rarely pure gold. You can find goldfish in orange, red, white, black, or even a mix of these colors.
The color of a goldfish depends on its scale type, and there are three main kinds:
- Metallic scales – shiny and solid in color (most common)
- Nacreous scales – a mix of shiny and matte, often called calico
- Matte scales – dull and soft-looking, with less shine
The most popular and common goldfish color is orange or orange-red, which is why many people picture goldfish that way. However, with so many combinations and patterns, goldfish colors can be truly unique.
Goldfish Fin Types: What Are the Different Fin Styles in Goldfish?
Goldfish have many different fin shapes, depending on their breed. The Common Goldfish has the same fin structure as its wild ancestor, the Prussian Carp (Carassius gibelio). All other goldfish varieties have been selectively bred to develop unique fin styles.
There are three basic goldfish fin types:
- Single Caudal Fin (Tail Fin) – This is the original fin type seen in Common Goldfish, Comets, Bristol Shubunkins, London Shubunkins, and American/Japanese Shubunkins.
- Twin Caudal Fins – These goldfish have a split tail that gives them a more elegant, flowing appearance.
- Twin Caudal Fins Without a Dorsal Fin – Some fancy goldfish have twin tails but lack the dorsal fin on their back. This creates a smoother, rounded silhouette.
Even within these categories, there are variations in length, shape, and fullness of the fins, giving each goldfish a unique look.
Goldfish Body Shapes: From Streamlined to Round
Goldfish body types are usually divided into three main shapes:
1. Long and Streamlined – These goldfish are fast swimmers and have a sleek body shape. They usually have single tail fins. Examples:
- Comet Goldfish
- Shubunkins
2. Short and Deep-Rounded – These are the classic fancy goldfish with chubby bodies and twin tail fins. Examples include:
- Oranda
- Black Moor
- Veiltail
3. Short, Rounded, and Dorsal-less – These fish are more delicate and don’t have a dorsal fin, making them look even rounder. Examples:
- Celestial Eye Goldfish
- Bubble Eye Goldfish
- Lionhead Goldfish
Goldfish Eye Types: The 4 Eye Styles You Should Know
Goldfish also come with different eye shapes, especially in fancy breeds. Here are the four basic goldfish eye types:
- Normal Eyes – Found in most common and comet goldfish.
- Telescopic Eyes – Seen in Moors and some other fancy goldfish, these eyes bulge outward.
- Upward-Facing Eyes – Known as Celestial Eyes, these goldfish have eyes that permanently look up.
- Bubble Eyes – These goldfish have fluid-filled sacs under their eyes that look like balloons.
Important Care Tip:
Do not mix normal-eyed goldfish with fancy types like Moors, Celestials, or Bubble Eyes in the same tank. The normal-eyed goldfish are faster and will outcompete the others for food.
Setting Up a Proper Environment for Goldfish
Creating the right environment is critical for your goldfish’s health:
- Aquarium Size: A minimum of 20 gallons for one goldfish and an additional 10 gallons per extra goldfish.
- Water Conditions: Maintain temperatures between 65°F and 75°F (18°C to 24°C) with a pH between 7.0 and 7.5.
- Filtration: Invest in a robust filter to manage the high waste production of goldfish.
Goldfish Diet and Feeding Habits
Goldfish are omnivores, which means they eat both plant-based and animal-based foods. To keep your goldfish healthy and active, it’s important to give them a balanced diet that includes both.
This is especially important for fancy goldfish with short, rounded bodies, as they are more likely to have digestive issues if their diet isn’t right.
What to Feed Your Goldfish
Here are common food types that goldfish enjoy:
- Dry foods: Flakes and pellets made for goldfish (easy but should not be the only food)
- Live foods: Brine shrimp, daphnia, or bloodworms (great for protein)
- Vegetables: Peas (without skins), spinach, lettuce, or zucchini (helps digestion)
- Gel foods: Soft, homemade or store-bought foods that are easy to digest
Feeding Tips Based on Season and Age
- In warm seasons, goldfish are more active and can eat a little more protein.
- In colder water, slow down feeding and give more plant-based food.
- Young goldfish need more protein to grow, while adult goldfish do well on a balanced mix.
- If you’re breeding goldfish, they will need higher protein intake to stay healthy and support egg production.
Avoid Overfeeding – The #1 Mistake
One of the most common causes of goldfish death is overfeeding, especially with dry foods like flakes or pellets. Uneaten food sinks and rots, quickly polluting the water and harming your fish. Read more on feeding.
🐟 Pro Tip:
Only feed your goldfish as much as they can eat in 1–2 minutes, once or twice a day. Always remove any leftover food to keep the water clean.
Are Goldfish Warm Water Fish?
Goldfish are often thought of as cold-water fish, but they actually do best in mild, stable temperatures. While they can survive in both very cold and very warm water for short periods, they thrive only within a certain temperature range.
What Temperature Is Best for Goldfish?
Goldfish can handle a wide range of water temperatures, but here’s what you should know:
✅ Ideal range: 55°F to 80°F (about 13°C to 27°C)
This is the most comfortable and healthy range for goldfish.
❄️ Cold water: They can survive in water just above freezing (around 32°F or 0°C) during winter, but only for a short time and with proper care.
🔥 Hot water: Goldfish can also live in temperatures up to 100°F (38°C), but the temperature must increase very gradually to avoid stress or shock.
Why Sudden Temperature Changes Are Dangerous
Goldfish are poikilothermic, which means their body temperature changes with the water. Because of this, they are highly sensitive to sudden temperature shifts.
⚠️ Important Rule:
Never move a goldfish from one body of water to another if the temperature difference is more than 5°F (around 3°C). This can shock their system and even be fatal.
Quick Tips to Keep Your Goldfish Safe
- Use a thermometer to monitor water temperature regularly.
- Avoid placing tanks near windows, heaters, or direct sunlight.
- If you’re changing the water or moving your fish, match the temperatures as closely as possible.
- Consider using a water heater or cooling fan if your room experiences extreme seasonal changes.
Read more on water conditions.
Do Goldfish Need Space? Yes – More Than You Think!
Goldfish may start small, but they need plenty of space to grow and stay healthy. A common mistake is keeping them in small bowls, which can lead to stress, poor water quality, and stunted growth.
How Much Space Do Goldfish Need?
As a rule of thumb, goldfish need about 24 square inches of surface area (top of the water) for every inch of body length.
Fancy goldfish like Orandas, Moors, and Lionheads need even more space because their rounded bodies take up more oxygen and create more waste.
🐠 Tip: It’s better to base tank size on surface area rather than volume. Goldfish need lots of oxygen, which is absorbed at the water’s surface.
Water Conditions and Oxygen Levels
Goldfish are very hardy and can live in many types of water, including:
- Hard or soft water
- Acidic or alkaline water
But they cannot tolerate low oxygen levels, which usually happen because of:
- Overcrowding
- Dirty, polluted water
- Lack of water movement
To avoid this:
- Use a good aquarium filter to keep water clean.
- Avoid adding too many fish to a small tank.
- Make sure the water is well-aerated, especially during warmer months.
Do Goldfish Lay Eggs? Understanding Goldfish Breeding
Yes! Goldfish are egg layers, not live-bearers.
- During breeding season, females scatter eggs among aquatic plants in shallow water.
- Males follow closely behind and fertilize the eggs as they are released.
- This process is called egg scattering, and it happens mostly in spring when water gets warmer.
⚠️ Warning:
Goldfish don’t care for their eggs or babies. In fact, they often eat their own eggs and fry if given the chance!
If you’re planning to breed goldfish:
- Move the eggs to a separate tank as soon as possible.
- Use a spawning mop or live plants to catch the eggs and protect them.
Read more on Goldfish breeding…
Goldfish Diseases: Common Illnesses and How to Treat Them
Goldfish are generally hardy pets, but they can still get sick — especially if they live in poor water conditions. Most goldfish illnesses are caused by stress, dirty water, or a weak immune system.
What’s the #1 Cause of Goldfish Death?
The leading cause of death in goldfish is polluted water, often due to overfeeding — especially with dry food like flakes or pellets. When food goes uneaten, it rots and produces ammonia, which is toxic to all fish. Even a small ammonia spike can make your goldfish sick or kill them quickly.
How to Treat Sick Goldfish at Home
In many cases, early treatment can save your goldfish. Here’s what to do:
- Do a partial water change (25% to 50%) to remove toxins.
- Add un-iodized cooking salt to the tank – about 1 tablespoon per gallon or 3–4 grams per liter.
- Add salt slowly to avoid shocking the fish. Goldfish can tolerate fairly high salt levels when introduced gradually.
- Stop feeding for a day or two if overfeeding is suspected.
This simple method can help treat many mild infections and stress-related illnesses.
Common Goldfish Illnesses to Watch For
Knowing the signs of illness can help you treat your goldfish before the problem becomes serious:
- Symptoms: Fish floats sideways, sinks to the bottom, or struggles to stay upright.
- Cause: Usually from poor diet or constipation.
- Treatment: Feed boiled, skinned peas, fast for a day, and improve water quality.
- Symptoms: Tiny white dots on the body and fins, scratching against surfaces.
- Cause: Parasite infection, often triggered by sudden temperature changes.
- Treatment: Use a commercial Ich treatment and slightly raise the water temperature.
How to Prevent Goldfish from Getting Sick
Prevention is always better than cure. Here’s how to reduce the chances of illness:
- Perform regular water changes (at least once a week).
- Use aquarium salt occasionally to boost immunity.
- Avoid overfeeding and remove any uneaten food.
- Keep water temperature stable, especially during seasonal changes.
- Monitor ammonia, nitrite, and nitrate levels regularly.
Goldfish Ponds vs Aquariums: Where Should You Keep Your Goldfish?
Goldfish are versatile pets that can be kept both indoors in aquariums and outdoors in ponds. However, each environment has different care needs — especially when it comes to temperature control and protection from predators.
Keeping Goldfish Indoors
If you’re keeping goldfish inside your home:
- A 15-gallon aquarium is the minimum recommended for a single goldfish.
- Indoor tanks have the advantage of stable temperatures, especially at night.
- Make sure the tank has a filter, regular water changes, and enough surface area for oxygen exchange.
🐟 Tip: Fancy goldfish varieties do especially well indoors, where the temperature stays stable and they’re safe from outdoor threats.
Keeping Goldfish Outdoors
Goldfish can also live happily in outdoor ponds or containers, but there are important things to consider:
- Small containers like a 15-gallon tub may work temporarily, but they cool down too quickly at night, especially in colder seasons.
- For long-term care, your outdoor pond should be at least 80 to 100 gallons to maintain a stable water temperature.
- Outdoor goldfish are more exposed to natural temperature changes, so larger volumes of water help reduce stress and health risks.
Protecting Outdoor Goldfish
Because goldfish have bright colors, they are easy targets for predators like birds and cats. To keep them safe:
- Use a pond net or cover to keep out birds, raccoons, and curious cats.
- Add plants or hiding spots to help fish feel secure.
- Be careful when training your goldfish to come to a specific spot to feed — your cat might learn the trick too!
Goldfish Behavior and Best Tankmates: What You Need to Know
Goldfish are known for their peaceful nature, which makes them a popular choice for home aquariums. However, not all fish make good companions for goldfish. Choosing the right tankmates is important for keeping a calm and healthy tank environment.
Goldfish Are Peaceful But Picky About Friends
While goldfish don’t usually show aggression, they do have specific compatibility needs:
- Avoid aggressive or fast-swimming fish like cichlids, barbs, or bettas. These species may nip fins or outcompete goldfish for food.
- Tropical fish are also a bad match, as they require warmer water than goldfish.
Best Tankmates for Goldfish
The safest and most compatible tankmates for goldfish are:
- Other goldfish varieties (e.g., Comets, Fantails, Orandas)
- Slow-moving, peaceful freshwater fish that enjoy similar cooler temperatures
- Bottom-dwellers like dojo loaches or white cloud mountain minnows (check size and space requirements)
🐠 Tip: Make sure tankmates are similar in size to your goldfish. Small fish may get eaten, and much larger fish can bully or harm goldfish.
Important Compatibility Tips
- Keep fancy goldfish (like Moors and Orandas) only with other fancy types, as they are slower and more delicate.
- Don’t mix single-tail goldfish (like Comets or Shubunkins) with fancy goldfish — single-tail types are faster and may outcompete fancies for food.
- Always watch for signs of bullying, such as fin damage or hiding behavior.
From Goldfish Basics to Goldfish Care: What’s Next?
Now that you’ve learned the goldfish basics, it’s time to dive deeper into goldfish care. Learn how to keep your goldfish healthy, happy, and thriving — whether in an aquarium or a pond.
Ready to take the next step?
👉 Explore our Goldfish Care Guide for tips on feeding, cleaning, and setting up the perfect tank.
👉 Or, visit our page on how to choose healthy goldfish and find out which varieties can live together peacefully.
Your journey to being a great goldfish owner starts here!
