The Goldfish with Big Eyes (All About the Telescope Goldfish)

Have you ever seen goldfish with big eyes and wondered why their eyes are so large? Why do their eyes look so odd? What is the benefit of having these big eyes? Why don’t all goldfish have them?

Are you curious about these large-eyed fancy goldfish, or do you want to add one to your aquarium? Either way, you’ll find out everything you need to know about them here.

What Are Telescope Goldfish?

Telescope Goldfish belong to the family Cyprinidae. They are sometimes referred to as Demekin, Dragon Eye Goldfish, or Globe Eye Goldfish.

They are the most recognizable kind of goldfish because of their huge, bulging eyes.

The thing that makes these fish interesting is that their big eyes serve no purpose. Humans have selectively bred these fish for their colors and body shape.

Unfortunately, the big eyes actually act as a hindrance. They leave Telescope Goldfish with poor eyesight.

They don’t do as well in the wild where they’re easily outcompeted for food. Still, they make interesting, peaceful additions to many aquariums.

Where Are Telescope Goldfish Found In The Wild?

These big eyed fancy goldfish were first developed in China in the early 1700s. The Chinese created the Telescope Goldfish through the breeding of Tosakins and Ryukin Goldfish. It was the Chinese who gave them the name “Dragon Eye Goldfish”.

The Japanese began developing these fish later in the 1700s and gave them the name “Demekin”.

In the wild, these fish inhabit stagnant, slow-moving water. Wild Telescope Goldfish are still found in Asian waters today. They are sometimes found in other areas as an invasive species.

What Do Telescope Goldfish Look Like?

We know these goldfish for their distinctive, bizarre-looking eyes. We call them “Telescope Goldfish” because their eyes look like a telescope. Their overly large eyes sit on top of long stalks at the sides of their head.

You won’t begin to notice the protrusion of their eyes until they’re about 6 months old. As adults, some of these fish will have eyes that protrude as much as ¾ in (19 mm) from their heads.

Telescope Goldfish look quite like Fantail Goldfish. Yet, they are smaller in size and have larger eyes. They have short, egg-shaped bodies with wide heads.

You can tell females and males apart because the female is larger and rounder than the male. The male will appear more streamlined and less stocky.

Most of these fish have a medium-length, split tail fin. Yet, you can sometimes find them with veil tails, broadtail, or butterfly tails that are longer.

These fish are very colorful, making them a favorite addition to aquariums. They come in a variety of colors from red, blue, brown, and white. Although they may come in solids, they often come in a variety of two or three colors. Juvenile fish are darker in color for better camouflage.

How Long Do Telescope Goldfish Live?

When kept in proper conditions, Telescope Goldfish can live for a long time. On average, they will live for 10-15 years. Yet, some Telescope Goldfish have lived past 20 years of age when kept in prime conditions.

How Big Can A Telescope Goldfish Get?

Telescope Goldfish reach smaller sizes than many other kinds. Still, they will grow quite large when kept in optimal conditions.

The average adult size of a Telescope Goldfish is 5 in (12.7 cm), but they may reach 8 in (20.32 cm).

What Size Tank Does A Telescope Goldfish Need?

If you’re starting off with a juvenile goldfish, the smallest size tank you should buy is a 10-gallon. Still, it’s better to start your fish off in a 20 or 30-gallon so that it has room to grow.

As your big eyed fancy goldfish grows, you must upgrade the tank. Goldfish can grow several inches long, so they need space to grow and swim. As an adult, anything less than 40-50 gallons is going to be too small.

It’s partially true that a goldfish will only grow to the size of its tank, but it’s a sad existence.

A goldfish’s body will stop growing in a small tank. But, its organs will continue to grow. This essentially suffocates the fish from the inside out. When a goldfish lives in a small tank, it will usually only survive for a few years. But, if it’s kept in a properly-sized tank, it can live for 10+ years.

You should also strive to house your goldfish in a tank that is longer than it is tall. Longer tanks provide your fish ample space to swim and provides more oxygen.

How Many Telescope Goldfish Can Live Together?

How many Telescope Goldfish you can keep together depends on the size of your tank. A 40-gallon aquarium is the ideal smallest size for a single Telescope Goldfish.

For each extra fish you’d like to include in your tank, you should have an extra 10-gallons.

Can You Provide Decorations?

Telescope Goldfish have poor eyesight. So, you should keep the decorations to a minimum. Avoid plastic plants because they have sharp edges that can damage their eyes if they bump into them.

Instead, try live plants as they provide a supplemental food source for your fish. You can also try silk plants which are soft and will not harm your fish.

What Kind Of Filtration Does A Telescope Goldfish Need?

Good filtration is a necessity for any kind of goldfish. They produce an enormous amount of waste.

It’s recommended to double the filter size for goldfish. In other words, if you’re keeping your goldfish in a 50-gallon aquarium, buy a 100-gallon filter.

Be sure to choose a filter with low to moderate flow. Telescope Goldfish are slow, awkward swimmers, so they don’t do well with a strong current.

Do Telescope Goldfish Need A Heater?

Goldfish are cold-water fish. It’s not necessary to provide a heater as long as you keep your home at room temperature.

A Telescope Goldfish can survive in temperatures as low as about 40° F (4.4° C). Still, their optimal temperature is 65-72° F (18°- 22° C).

Never allow the temperature to drop quickly within the aquarium. Your fish are likely to go into shock and may die.

What pH Do Telescope Goldfish Need?

Telescope Goldfish are not picky about their pH levels and can tolerate a range of 6.0-8.0.

What Food Do Telescope Goldfish Eat?

Telescope Goldfish are omnivores, so they eat a variety of plant and animal matter. They are opportunistic feeders that will eat almost anything that can fit in their mouth.

As a general rule, it’s a good idea to feed them a high-quality fish flake on a regular basis. It’s also necessary to offer them regular greens such as aquatic vegetation or lettuce. As an occasional treat, you can offer them frozen brine shrimp, blood worms, or Daphnia.

What Are Good Tankmates For Telescope Goldfish?

In general, it’s only recommended to keep goldfish with other goldfish. Sometimes, you can get away with keeping them with other cold-water fish. But, you have to be careful that the tankmates won’t outcompete the goldfish for food. Worse yet, if the tankmate is too small, it will become a meal for the goldfish.

You even need to be cautious when keeping fancy goldfish together. Some types of goldfish go better together than others.

The Issue With Goldfish With Big Eyes

Unfortunately, a Telescope Goldfish’s big eyes make it unideal as a beginner fish. Their large eyes leave them with poor vision. Their eyes are also prone to injury and infection.

You should only keep them with goldfish who also have large eyes. Other goldfish — like the common goldfish — will outcompete the Telescope Goldfish for food.

If you’re a beginner aquarist, the best goldfish to keep with your Telescope Goldfish is the Black Moor. More experienced aquarists can try the Bubble Eye Goldfish, the Lionhead Goldfish, or the Celestial Goldfish.

If you’re looking for a tankmate for your goldfish, make sure to check out: Can Angelfish Live With Goldfish (regular, not fancy goldfish)


Telescope Goldfish are born with a disadvantage. They have poor eyesight, difficulty finding food, and are prone to infection.

Still, they can make wonderful, interesting pets if you give them the care they need.

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