Pop Eyed Fish (Telescope Goldfish) Care Guide

Pop eyed fish are fancy goldfish bred for large, upward- or sideways-bulging eyes. They are hardy, cool-water fish that don’t need a heater, but they are messy, grow to about 6 inches or more, and need more tank space than most people expect.

Their eyes are also delicate. This guide covers what you need to keep them healthy, and how to tell their natural bulging eyes from pop eye disease, which is a medical problem.

Pop Eyed Fish Facts & Overview

Pop eyed fish, more commonly sold as telescope eye goldfish, are a type of goldfish in the Cyprinidae family, which also includes minnows and carp. They are a fancy goldfish, a group known for egg-shaped bodies and double tails. For this variety, the defining feature is the pair of protruding, telescopic eyes.

The black telescope is sold as the Black Moor goldfish, so look for that name in stores too. Telescopes also come in orange, red, calico, white and panda patterns.

There is no wild population. Goldfish were bred from carp-like fish in China over many centuries, and the telescope eye is a trait selected by breeders.

Telescopes are widely sold and usually inexpensive, but they are not the low-maintenance fish their price suggests. They are hardy if the water is clean, and they are messy eaters that produce a lot of waste. Buy from a tank where the fish are active, eating and free of cloudy eyes, torn fins or clamped tails.

With good care, 10 to 15 years is common, and 15 to 20 is possible in a large, well-kept tank.

Typical Behavior

Telescopes are peaceful. They are slow swimmers with poor eyesight, so they get outcompeted at feeding time and bullied by fast or nippy fish.

They are social and do better with other goldfish than alone. Goldfish show shoaling behavior, and keepers generally house them in groups. They swim in the middle and lower parts of the tank and constantly root through the substrate for food. Stressed fish hide.

Appearance

These fish are easy to tell apart from other goldfish. Their large eyes bulge out from the head, which is why they are also called telescope goldfish. Despite the big eyes, their vision is poor.

The body is egg-shaped, and the fins are long and flowing with a double tail. Black Moors are solid black, though some turn bronze or rust when kept in bright light or as they age. Other telescopes may be orange, red, calico or white.

Telescopes are usually 4 to 6 inches long and can reach 8 inches. Their eyes may not reach full size until they are around 2 years old.

Sexing is hard until breeding season. Mature males develop small white bumps, called breeding tubercles, on the gill covers and the front edge of the pectoral fins. Females look rounder and fuller when carrying eggs.

Pop Eye Disease vs. Telescope Eyes

Telescope eyes are normal for this variety. Pop eye disease (exophthalmia) is not. It means fluid is building up behind the eye and pushing it outward.

Signs that the bulging is a problem:

• One eye is suddenly larger than the other.
• An eye looks cloudy or has blood in it.
• The fish stops eating, hides, or has other symptoms such as clamped fins.

One swollen eye usually means an injury, such as a snag on a sharp decoration. Both eyes swelling at once points to a bacterial infection or poor water quality, and these cases may need antibiotics. Test ammonia and nitrite, do a large water change, and remove anything sharp. Epsom salt baths are often used to reduce swelling, but ask a fish vet or an experienced keeper before using any medication.

Habitat and Tank Conditions

Goldfish are cool-water fish. They live well at room temperature in most homes, and a heater is usually unnecessary.

Tank Conditions

• Temperature: 65-72°F is the sweet spot for fancy goldfish. Up to about 75°F is acceptable. Cooler temperatures slow their metabolism, so avoid sudden swings.
• pH: Sources give a range of about 6.5-8.0. Stable water matters more than hitting an exact number.
• Substrate: Use smooth gravel or sand. Telescopes dig through the substrate, so avoid sharp gravel and any pieces small enough to swallow.
• Decor: Choose smooth rocks and driftwood and avoid sharp edges that can injure eyes. Hardy plants like anubias work, or use plastic and silk plants because goldfish eat and uproot most live plants.
• Filtration: Use a strong filter with a lot of capacity, because goldfish produce a lot of waste. Add an air stone or an air pump for extra oxygen if you like.

What Size Aquarium Do They Need?

Plan on at least 20 gallons for the first fish and 10 more gallons for each additional fish. A long tank is better than a tall one. Bigger is always better, since the fish are messy and grow to 6 inches or more.

Plan for 50% weekly water changes with a conditioner, and test the water weekly. An unfiltered bowl is not suitable.

Tank Mates

The best tank mates are other slow, fancy goldfish like ryukins and fantails. Telescopes are slow swimmers with bad eyesight, so fast common goldfish can steal their food. Avoid long-finned varieties like veiltails with them if you can, because they are prone to fin problems.

Many popular community fish are tropical, and goldfish prefer cooler water, so check the temperature requirements before mixing species. Tetras, mollies, guppies and dwarf gouramis generally need warmer water than fancy goldfish do. Some danios and cory catfish tolerate cooler water, but goldfish may eat small fish. Avoid fin nippers, including many barbs.

Most snails are fine. Shrimp will be eaten.

Can You Keep Pop Eyed Fish Together?

Yes, and it is generally recommended. Keep them with other fancy goldfish of similar size and speed. Make sure the tank is big enough for everyone.

Diet

Pop eyed fish are omnivores and eat most aquarium foods. The best base is a quality sinking goldfish pellet, since fish that gulp air at the surface can develop buoyancy problems. Add:

• Frozen or live foods a few times a week, such as bloodworms and brine shrimp.
• Blanched green vegetables such as peas without skins, spinach or zucchini.

Soak dry foods in tank water for a minute before feeding. Feed small amounts once or twice a day, and remove uneaten food. Because telescopes are slow and have poor eyesight, drop food near them and watch that faster tank mates don’t take it all.

Care

Clean water prevents most problems. Do weekly water changes, siphon waste from the substrate, and test the water.

Their eyes are their weak point. Because they stick out, they get injured easily. Remove sharp decor, avoid netting the fish, and don’t use cramped tanks where they bump into things. Black Moors and other telescopes sometimes lose an eye over their lives. Fish with one eye can still do fine if the tank is safe.

Fancy goldfish also have compressed bodies, which makes them prone to swim bladder problems. Affected fish may float, sink or swim tilted, as the swim bladder is key for maintaining buoyancy. Fasting for a day, feeding soaked sinking pellets and blanched peas, and keeping the water clean fix many cases.

Treat sick fish in a separate quarantine tank so you don’t spread disease to others, and remove carbon from the filter if you medicate.

Breeding

Goldfish breed readily in ponds and large tanks once they are mature and conditions are right. A cool winter followed by warming water in spring usually triggers spawning.

The male chases the female and nudges her to release eggs. A female may lay several hundred to a thousand or more adhesive eggs on plants or spawning mops. The parents will eat them, so move the eggs or the adults.

Eggs hatch in about 4 to 7 days, depending on temperature. Feed fry infusoria or liquid fry food at first, then baby brine shrimp. Only a few of the fry will have telescope eyes, and eyes may not develop until months later.

Are Pop-Eyed Fish Suitable for Your Aquarium?

Pop eyed fish suit keepers who have room for a 20-gallon or larger tank, a strong filter and time for weekly water changes. They are peaceful, unusual-looking and easy to feed. They are not ideal for tiny tanks or for mixing with fast, tropical or nippy fish.

Are Pop Eyed Fish your favorite type of goldfish? Let us know in the comments below.