From their disproportionately large eyes to their gracefully undulating fins, the big eyed goldfish holds a special place in the hearts of hobbyists and professional aquarists alike. Known for their charm, resilience, and striking appearance, these fish require thoughtful care to stay healthy and happy. This guide dives into everything you need to know about the big eyed goldfish—from choosing the right variety and setting up a suitable habitat to feeding, health concerns, and breeding tips. Whether you are a first‑time keeper or expanding a specialist collection, you’ll find practical advice to help you enjoy this captivating species for years to come.
What Are Big Eyed Goldfish?
The term big eyed goldfish encompasses several ornate varieties that share one distinctive feature: eyes that appear larger and more forward‑projecting than those of standard goldfish. In some strains, the eyes protrude more than others, giving the fish a unique, almost cartoon‑like expression. These are not separate species; they are fancy goldfish bred for a dramatic eye architecture and a variety of body shapes and colourations. The result is a striking group of fish that can truly become the centrepiece of a well‑planned aquarium.
In the hobby, you will often hear about the classic Black Moor, Demekin, and other eye‑focused varieties. Although collectively described as big eyed goldfish, each type has its own temperament, care requirements and presentation. Importantly, their eyes are especially sensitive to water quality and physical injury, so attentive husbandry is essential. If you are contemplating adding a big eyed goldfish to a home aquarium, understanding the differences between varieties helps you tailor the setup, feeding, and tank mates to the specific fish you choose.
Big Eyed Goldfish Varieties: A Quick Guide
There is a delightful array of big eyed goldfish varieties, each with its own character. Here are some of the most commonly encountered in UK fish shops and among private keepers:
Black Moor (Demekin‑style)
The Black Moor is one of the most recognisable big eyed goldfish. Its velvety black colour and bulbous, protruding eyes give it a ghostly, elegant silhouette. Black Moors are generally slow and peaceful, preferring a calm environment with gentle water movement. The eyes are highly delicate, so they benefit from smooth decorations, careful handling, and a well‑maintained aquarium to prevent eye injuries.
Demekin (Japanese lineage of the Black Moor)
Demekin is the Japanese term often used to describe the black, eye‑heavy varieties that share the same forward‑facing gaze. They tend to have a deeper body than some other fancy goldfish and can be quite hardy when kept in ideal conditions. The key with Demekin and related varieties is to provide generous swimming space and excellent filtration, ensuring that the water remains pristine so that the eyes remain healthy.
Telescope‑eyed and Ultra‑long‑finned Impersonators
Some big eyed goldfish display an extended eye structure or an elongated body plan. These fish may be grouped loosely with the big eyed category due to the eye emphasis, but they can differ in shape and fin configuration. Regardless of the exact subtype, the common thread is a need for stable water parameters, careful handling, and avoidance of sharp décor that could harm the eyes.
Setting Up the Aquarium for Big Eyed Goldfish
Creating the right environment is the cornerstone of keeping big eyed goldfish healthy. They are generally slow swimmers and produce a lot of waste, so habitat design should prioritise water quality, gentle currents, and protective spaces. Here’s how to set up a tank that showcases their beauty while supporting long, healthy lives.
Tank Size and Layout
In the world of big eyed goldfish, space matters. A single big eyed goldfish is best housed in a spacious aquarium, with a recommended starting point of at least 60‑100 litres (around 15‑22 gallons) for one fish. The bigger, the better: many keepers aim for 150 litres (about 40 gallons) or more for a single specimen to give it ample room to swim and grow. If you plan to keep two or more individuals, increase the volume accordingly—roughly 150‑300 litres (40‑80 gallons) or more, depending on the number and size of the fish.
When arranging the aquascape, use smooth, rounded decorations and *avoid* sharp edges that could injure the eyes on contact. Live plants can be a nice touch if you choose species that won’t be uprooted by the fish’s softer but purposeful browsing. Allow for open swimming space, with a gentle, curved layout rather than a cluttered, tight‑packed décor scheme. For the big eyed goldfish, a sinking substrate is often preferred to deter rummaging and to maintain a calm, stable environment.
Filtration and Cycling
Filtration is absolutely essential for big eyed goldfish. They produce a lot of waste, and once the eyes have been compromised by poor water quality, recovery can be difficult. A reliable external canister or high‑quality internal filter that provides mechanical, chemical, and biological filtration is ideal. Aim for a turnover rate that creates mild water movement without creating strong currents, as these fish tend to prefer slower flows and can be stressed by heavy agitation.
Before introducing big eyed goldfish to a new tank, ensure the system is fully cycled. The chemical stability of the water is vital for their long‑term health. Regular monitoring with a liquid test kit for ammonia, nitrite, nitrate, and pH will help you catch problems early. A weekly 10‑20% partial water change (more often if the bioload is high) keeps the environment clean and the fish comfortable.
Substrates, Plants and Hiding Spots
Choose a smooth, fine substrate such as rounded pea gravel or fine sand to minimise eye irritation. Planting with hardy, slow‑growing species is ideal, but remember that big eyed goldfish will root around in the substrate and nibble on plant leaves. Floating plants can provide shade and a sense of security without occupying valuable swimming space. Include a few gentle hiding spots—cave features with rounded edges, driftwood, or broad‑leaved plants—where a nervous individual can retreat if it feels overwhelmed.
Lighting, Temperature and Routine
Big eyed goldfish appreciate a stable light cycle, with around 10‑12 hours of light per day being a common standard. A consistent day‑night rhythm supports normal behaviour and feeding patterns. Temperature should be kept within a comfortable range for fancy goldfish, typically between 18–22°C (64–72°F). Sudden temperature fluctuations should be avoided, as rapid shifts can stress the fish and compromise their immune system. If housed in a pond during warmer months, ensure the pond is well aerated and that the fish can retreat to cooler, shaded corners during heat spikes.
Diet and Feeding for Big Eyed Goldfish
A balanced, varied diet is essential to keep the big eyed goldfish in peak condition. Their digestive systems are designed for grazing and frequent, smaller meals rather than large, infrequent feedings. Here’s how to nourish your eye‑forward friends without compromising their health.
What to Feed
Offer a mix of high‑quality sinking and slow‑sinking pellets formulated for goldfish, supplemented with occasional fresh or blanched vegetables (such as peas, cucumber, courgette) and live or frozen options like daphnia or bloodworms as treats. Rotating foods helps prevent nutritional deficiencies and keeps mealtimes interesting for the fish. Avoid ornamental pond fish foods that are high in fats or additives not tailored to the omnivorous, herbivorous tendencies of goldfish.
For big eyed goldfish with delicate eyes, avoid using overly bright, heavily coloured foods that could stain or irritate the eyes over time. Always rinse produce and feed in moderation to prevent water quality issues. A well‑balanced staple diet, plus occasional treats, supports vibrant colours, good growth, and a robust immune system.
Feeding Schedule and Practices
Feed small portions two to three times daily, only what the fish can consume within two to three minutes. This approach reduces waste and keeps nitrate levels manageable. Monitor appetite and adjust portions accordingly, especially as the fish age or if you notice a slowdown in feeding. If the big eyed goldfish stops eating for more than a day, it can be a sign of stress or illness, and you should check water quality and consider a veterinary check if the issue persists.
In colder months, reduce feeding frequency slightly since digestion slows with lower temperatures. Conversely, in warmer periods, you may need to feed a touch more (still in small portions) as activity and metabolism increase. Routine feeding consistency helps fish maintain a stable feeding pattern and a healthy weight.
Health and Common Problems for Big Eyed Goldfish
Healthy eyes are a priority for big eyed goldfish. When kept in suboptimal conditions, these eyes can become vulnerable to injury and infection. Being proactive about water quality, observation, and timely intervention is essential to prevent long‑term problems. Here are the most common health concerns and how to recognise and address them.
Eye Health: Protection Against Injury and Infection
Because the eyes are prominent, they are particularly prone to injury. Sharp décor, rough substrate, or aggressive tank mates can cause corneal damage or infections. Regularly inspect the eyes for swelling, cloudy patches, or redness. If you notice discharge, a change in eye appearance, or blinking or rubbing behaviours, investigate the water quality immediately and consult a veterinarian if the issue persists. Gentle, prompt treatment is key to preserving vision and overall wellbeing.
Swim Bladder and Buoyancy Issues
Swim bladder problems can cause a big eyed goldfish to swim unsteadily, float near the surface, or sink to the bottom. These issues can stem from overfeeding, poor diet, or rapid changes in water temperature. A consistent feeding routine, high‑quality foods, and careful water management can mitigate these concerns. If a fish shows persistent buoyancy problems, seek advice from a fish health professional to determine the underlying cause and the most appropriate treatment.
Parasites, Fungal and Bacterial Infections
Keep a watchful eye for signs of parasites (scratching against decor, frayed fins), fungal growth (white cottony patches), or bacterial infections (redness, ulcers). Early detection improves outcomes. Quarantine new arrivals to prevent introducing pathogens to established populations. If you suspect parasites or infection, a diagnostic test and appropriate treatment—guided by a veterinarian or experienced aquarist—will support recovery while minimising stress to the big eyed goldfish.
Aquarium Ticks: Poor Water Quality and Ongoing Maintenance
Unstable water parameters are a frequent cause of health problems in big eyed goldfish. Regular testing for ammonia, nitrite, nitrate, and pH is vital. Partial water changes—typically 10‑20% weekly, or more frequently in heavily stocked tanks—help maintain clarity and health. A robust filtration regime coupled with routine maintenance (including cleaning filter media as recommended by the manufacturer) keeps the environment clean and predictable for these sensitive fish.
Behaviour, Temperament and Tankmates
Big eyed goldfish are generally peaceful, sociable, and curious. They are not aggressive and tend to mingle well with other slow or similar‑paced fish. However, there are important considerations to ensure compatibility and avoid stress or injury.
Suggested Tank Mates
When selecting companions for a big eyed goldfish, opt for other slow‑swimming, non‑aggressive species that inhabit the mid to lower water column. Options might include other fancy goldfish varieties, certain peaceful loaches, or other small, non‑fin nipping species. Avoid fast, long‑tailed fish that can outpace or harass the big eyed goldfish, as well as particularly boisterous species.
Behavioural Notes
Expect regular foraging, gentle exploring of the aquascape, and occasional displays of curiosity toward new items in the tank. Big eyed goldfish appreciate stable routines and predictable lighting. Sudden changes in décor, water temperature, or feeding schedules can unsettle them, leading to stress behaviours such as hiding, lethargy, or unusual swimming patterns. A calm, well‑settled environment supports natural activity and the visual appeal of these eye‑forward beauties.
Breeding Big Eyed Goldfish: A Brief Overview
Breeding big eyed goldfish can be a rewarding but challenging project. It requires careful planning, knowledge of the specific varieties, and a separate, well‑monitored breeding setup to protect fry and keep parents from overeating eggs.
Sexing and Readiness
Sexing fancy goldfish can be tricky, particularly with eye‑focused varieties. In many cases, females become fuller in the abdomen during the breeding season, while males may develop small, white tubercles on the gill covers and fins. For big eyed goldfish, the cues can be subtle, so patience and experience pay off.
Eggs, Hatch, and Fry Rearing
If breeding is undertaken, a separate breeding tank is typically required. The eggs are often adhesive and can be targeted by adults quickly, so precise supervision or a separate setup is essential. Fry require tiny foods such as newly hatched brine shrimp or finely ground commercial foods. Lifecycle care for big eyed goldfish fry includes maintaining pristine water, gentle aeration, and gradual introduction to standard feeds as they grow. Successful rearing depends on the breeder’s ability to manage parental behaviour and water quality during the critical early weeks.
Maintaining Water Quality: The Heart of a Healthy Aquarium
A clean, stable aquatic environment is the bedrock of successful big eyed goldfish keeping. Water quality is not just a backdrop; it actively influences growth, colour, energy levels, and eye health. Here are practical steps to maintain excellent conditions:
Regular Testing and Parameter Targets
Invest in a reliable liquid test kit. Track ammonia and nitrite levels (aiming for 0 ppm) and keep nitrate below 20–40 ppm, depending on the system and fish load. Maintain a pH between roughly 7.0 and 7.6, adjusting gradually if needed. Temperature should be steady within the recommended range (around 18–22°C). If you operate a pond system in warmer months, monitor temperature fluctuations carefully and ensure adequate aeration to prevent oxygen depletion.
Partial Water Changes and Filtration Maintenance
Consistent partial water changes are the most straightforward way to keep water quality high. A weekly change of about 10–20% is standard for average bioloads, with more frequent changes if you notice a rise in nitrates or if the tank is heavily stocked. Clean filter media as instructed by the manufacturer to preserve beneficial bacteria. Avoid cleaning the entire filtration system in one go, which can disrupt the biological balance; instead, rinse media in a bucket of tank water to preserve colonies.
Handling and Quarantine Practices
Quarantine new arrivals before adding them to an established tank. A small quarantine tank helps you observe for signs of disease and prevent introducing pathogens to your main display. When handling big eyed goldfish, use gentle movements and minimal handling; their eyes are delicate and susceptible to scratches or damage. A calm approach reduces the risk of injury and stress, supporting long‑term health and wellbeing.
Common Myths and Misconceptions About Big Eyed Goldfish
As with many beloved species, a few myths persist about big eyed goldfish. Separating fact from fiction helps you deliver better care and avoid unnecessary harm to your fish.
- Myth: Big eyed goldfish can thrive in small bowls. Reality: Even though their eyes may be captivating, they require larger volumes of water, robust filtration and stable conditions. A bowl view is inadequate for any serious goldfish keeping.
- Myth: They do not grow large; you can house them in modest tanks. Reality: Big eyed goldfish do grow and need space to move and develop. Under‑feeding and cramped conditions often lead to stunted growth and health problems.
- Myth: They are low maintenance. Reality: While hardy, they are not “set and forget” fish. Consistent water care, appropriate feeding, and regular health checks are essential for long‑term vitality.
Buying and Caring for Your Big Eyed Goldfish
When buying big eyed goldfish, whether from a local retailer or a reputable breeder, look for signs of health and vitality. A well‑conditioned fish should be active, with clear eyes (not swollen or cloudy), clean fins, and a smooth, uninjured body. Avoid fish that show signs of lethargy, rapid gill movement, or visible skin lesions. If possible, observe the fish in a well‑lit tank for a few minutes to assess how it swims and interacts with others.
Consider provenance and ethics as part of your buying decision. Reputable breeders and established shops with good welfare standards are more likely to provide healthy stock and guidance on proper care. When you bring your new big eyed goldfish home, acclimate it slowly to the new water by gradually mixing tank water with the transport water. Monitor the new fish for a couple of days to ensure it is feeding and adjusting well.
Concluding Thoughts: The Joy of Keeping Big Eyed Goldfish
The big eyed goldfish is a remarkable addition to any thoughtfully designed aquarium. With their striking eyes, serene presence, and gentle temperament, these fish bring a sense of grace and wonder to the home aquarium. The journey of keeping big eyed goldfish well is a blend of science and art: careful attention to water quality, dietary balance, and a peaceful environment, all delivered with a patient, observant approach. By investing in proper tank size, reliable filtration, stable conditions, and a varied, nutritious diet, you can enjoy the beauty and charm of big eyed goldfish for many years.
Frequently Asked Questions About Big Eyed Goldfish
Do big eyed goldfish require a large tank?
Yes. Big eyed goldfish thrive in larger volumes of water where waste is more easily diluted and the eyes remain protected from injury. Plan for a minimum of around 60‑100 litres for a single fish, with more space needed for additional specimens or if you want to maintain a visually dramatic display.
Are big eyed goldfish suitable for beginners?
They can be, provided you commit to solid tank setup, regular maintenance, and awareness of their specific needs. Beginners should start with a stable environment, high‑quality filtration, and gradual learning about feeding and water management.
What are the most important health signs to watch for?
Active swimming, regular feeding, clean gill movement, and eyes that appear clear and spotless are good indicators. Watch for sudden changes in appetite, swimming patterns, or eye appearance, which may signal a problem requiring attention.
Can I keep big eyed goldfish with other fish?
Yes, with caution. Choose slow or similarly peaceful species that won’t harass or outcompete the goldfish for food. Avoid aggressive or very fast species that could trigger stress or injury.
A Final Note on the Joy of Keeping Big Eyed Goldfish
Whether you are drawn to their striking gaze, the elegance of their fins, or the gentle nature that many owners adore, big eyed goldfish offer a rewarding hobby. With thoughtful planning, a well‑equipped tank, and a daily commitment to the health and welfare of your fish, this family of eye‑forward beauties can flourish for many years. By prioritising space, water quality, consistent feeding, and compassionate husbandry, you’ll enjoy the artful presence of the big eyed goldfish in your living space—an enduring symbol of patience, care, and the quiet joy of aquariums kept at their best.