Common Goldfish Care Guide — Tank Setup, Feeding and Breeding

Quick summary

The Common Goldfish is a hardy, easy to care for coldwater fish, but it needs a much bigger home than most people expect, at least 150 litres, plus decades-long commitment, since it can grow up to 35 cm and live well over 10 years. If you can provide spacious, well-filtered accommodation rather than a bowl or small tank, it makes a hardy and genuinely interactive pet for beginners and experienced keepers alike.

🐠 Build a tank around this fish

In this guide:

Introduction
Quick Stats
Appearance
Varieties and Morphs
Natural Habitat
Tank Size and Setup
Water Parameters
Filtration and Equipment
Diet and Feeding
Behaviour and Temperament
Tank Mates
Breeding
Common Diseases
FAQs

Introduction

The Common Goldfish (Carassius auratus) is arguably the most recognisable freshwater fish in the world. Originating from East Asia, this coldwater species has been kept in captivity for well over a thousand years, making it one of the earliest domesticated fish. Despite its ubiquity in pet shops and fairground prizes, the Common Goldfish is widely misunderstood, and far too many keepers underestimate its space requirements, lifespan, and potential adult size. When properly cared for, Common Goldfish are hardy, personable, and remarkably long-lived fish that can become genuine companions for decades.

Unlike the many fancy goldfish varieties that have been selectively bred for exaggerated body shapes and finnage, the Common Goldfish retains a streamlined, athletic build closely resembling its wild ancestor, the Prussian carp. This body shape makes it an active, fast-swimming fish that thrives in spacious environments with excellent water quality. It is a coldwater species that does not require a heater in most temperate climates, and it is equally at home in a suitably large aquarium or a well-maintained garden pond.

This care guide covers everything you need to know to keep Common Goldfish healthy and thriving in a freshwater aquarium setting, including tank size requirements, water parameters, diet, compatible tank mates, breeding, and common health issues. Whether you are a beginner considering your first fish or an experienced keeper looking to refine your goldfish husbandry, the information below will help you provide the best possible care for this classic species.

Quick Stats

Scientific name	Carassius auratus
Common names	Common Goldfish, Feeder Goldfish, Comet Goldfish (often confused), Hibuna
Family	Cyprinidae
Origin	East Asia (China, originally from wild Prussian carp populations)
Adult size	20–35 cm (8–14 inches), occasionally larger in ponds
Lifespan	10–25 years, with reports exceeding 40 years
Difficulty	Easy
Breeding difficulty	Easy
Temperature	10–24 °C
pH range	6.5–8.0
General hardness (GH)	5–19 dGH
Carbonate hardness (KH)	4–12 dKH
Minimum tank size	150 litres
Conservation status	Least Concern (IUCN)

Appearance

The Common Goldfish possesses a robust, torpedo-shaped body that is laterally compressed but retains the sleek, hydrodynamic profile of its wild carp ancestors. This body form distinguishes it immediately from the rounder, egg-shaped fancy goldfish varieties. The dorsal fin is single and moderately tall, the caudal (tail) fin is forked and relatively short compared to longer-finned varieties, and the paired pectoral and pelvic fins are proportionate to the body. The anal fin is also single. Overall, the finnage is neat and functional rather than ornamental.

The most iconic feature of the Common Goldfish is, of course, its colour. The classic form displays a vivid orange to reddish-gold metallic colouration across the entire body and fins, which develops as the fish matures. Juvenile Common Goldfish are typically olive-brown or bronze in colour, closely resembling their wild ancestors, and they gradually develop their orange pigmentation over the first year or two of life. Some individuals may retain dark patches or develop white markings as they age. The scales are large, clearly defined, and possess a bright metallic sheen that catches the light beautifully.

Common Goldfish have relatively large, prominent eyes positioned on either side of the head, giving them a wide field of vision. The mouth is terminal and lacks barbels, which distinguishes goldfish from true carp species like koi. Adults typically reach 20 to 35 centimetres in length in aquarium conditions, though pond-kept specimens can grow even larger. The body is muscular and well-proportioned, reflecting the species’ active swimming habits and its need for ample space.

Sexual dimorphism is subtle outside of the breeding season. During spawning condition, mature males develop small white tubercles (breeding stars) on the gill covers and leading edges of the pectoral fins. Females tend to appear fuller and rounder when viewed from above, particularly when gravid with eggs. Outside of breeding condition, it can be challenging to distinguish the sexes reliably.

Varieties and Morphs

While the Common Goldfish in its classic orange form is the most widely recognised, several colour morphs and closely related varieties are commonly encountered in the aquarium trade. It is worth noting that the Common Goldfish, the Comet Goldfish, and the Shubunkin are often grouped together as “single-tailed goldfish” due to their similar body shape and care requirements, though each has distinct characteristics.

The standard Common Goldfish is available in a range of metallic colour forms beyond the classic orange. Red Common Goldfish display a deeper, more intensely saturated crimson hue, while yellow or lemon goldfish exhibit a pale golden-yellow colouration. White or silver Common Goldfish lack the orange pigmentation almost entirely and appear pearly white with a metallic sheen. Red-and-white bicolour forms, sometimes called Sarasa-type Commons, feature patches of deep red against a white base, though this pattern is more commonly associated with the Comet variety. Chocolate or bronze-coloured individuals retain the juvenile colouration into adulthood and can be quite striking.

The Comet Goldfish is frequently sold alongside and sometimes mislabelled as the Common Goldfish. Comets are distinguished by their longer, more deeply forked caudal fin, which can be nearly as long as the body itself. They tend to be slightly slimmer and faster swimmers. Comets are available in the same colour range as Commons, with the Sarasa Comet (red and white) being particularly popular.

The Shubunkin is another single-tailed variety that shares the Common Goldfish’s body shape but features calico colouration, a mottled pattern of blue, orange, red, black, and white. The most prized Shubunkins display a strong blue base colour. The London Shubunkin has finnage identical to the Common Goldfish, while the Bristol Shubunkin has broader, more rounded fins, and the American or Japanese Shubunkin has longer, flowing finnage similar to the Comet.

So-called “feeder goldfish” sold in pet shops are typically Common Goldfish or Comet Goldfish that have been bred in large quantities with less attention to colour quality. These fish are genetically identical to their more carefully bred counterparts and, given proper care, will grow just as large and live just as long. They should never be purchased with the assumption that they are a smaller or shorter-lived variety.

Natural Habitat

The wild ancestor of the Common Goldfish is the Prussian carp (Carassius gibelio), a species native to slow-moving and still freshwater habitats across East Asia, particularly in China. Wild populations inhabit lakes, ponds, reservoirs, slow-flowing rivers, ditches, and marshy wetlands. These habitats are characterised by relatively shallow, still or gently flowing water with muddy or silty substrates and abundant aquatic vegetation.

In their natural range, these fish experience significant seasonal temperature fluctuations, from near-freezing winter temperatures to warm summers. This adaptation to a wide temperature range is what makes the domesticated Common Goldfish so hardy in captivity. The water in their native habitats is typically neutral to slightly alkaline, moderately hard, and often somewhat turbid due to suspended sediment and organic matter.

Wild Prussian carp are omnivorous foragers, feeding on a mixture of aquatic invertebrates, insect larvae, crustaceans, plant matter, algae, and detritus. They root through the substrate searching for food, a behaviour that is readily observed in captive goldfish. Vegetation in their natural habitat includes a range of submerged, emergent, and floating plants, which provide cover from predators, spawning sites, and supplementary food.

It is important to note that Common Goldfish have been introduced to waterways on every continent except Antarctica and are considered an invasive species in many regions. Released or escaped goldfish can reproduce prolifically in suitable habitats, outcompeting native species and disrupting ecosystems. Common Goldfish should never be released into the wild under any circumstances.

Tank Size and Setup

One of the most persistent myths in fishkeeping is that goldfish can live happily in a small bowl or a compact aquarium. This is categorically untrue. The minimum recommended tank size for a single Common Goldfish is 150 litres (approximately 40 US gallons), with an additional 50–75 litres for each additional fish. Common Goldfish are large, active, and produce a substantial amount of waste, and they require spacious, well-filtered environments to thrive. A pair of Common Goldfish will ideally need a tank of 200–250 litres or more. For groups, a pond or very large aquarium of 400 litres or above is strongly recommended.

When choosing a tank, prioritise length and surface area over height. Common Goldfish are active horizontal swimmers and benefit from tanks that are long and wide rather than tall and narrow. A standard rectangular aquarium is ideal. The tank should have a secure, well-fitting lid or cover, as goldfish can occasionally jump, particularly when startled or during spawning activity.

For the substrate, smooth gravel or sand is the best choice. Avoid sharp or angular gravel that could injure the fish as they forage. Common Goldfish love to root through the substrate searching for food, so a fine, rounded gravel or sand substrate accommodates this natural behaviour. Some keepers prefer bare-bottom tanks for ease of cleaning, which is a perfectly valid approach, especially in heavily stocked setups.

Decorations should be chosen with care. Avoid ornaments with sharp edges, small openings that a growing goldfish could become trapped in, or rough surfaces that could damage scales or fins. Smooth rocks, driftwood, and purpose-made aquarium decorations are all suitable. Live plants can be included, but be aware that Common Goldfish are notorious plant eaters and uprooters. Hardy, robust species such as Anubias (attached to hardscape), Java Fern, and Vallisneria have the best chance of survival, though even these may be nibbled. Many keepers opt for artificial plants or accept that live plants will be treated as a supplementary food source.

Adequate lighting is beneficial for both the fish and any live plants, but Common Goldfish do not have specific lighting requirements. A standard aquarium LED light on a timer providing 8–10 hours of light per day is perfectly sufficient. Ensure the tank is not placed in direct sunlight, as this can cause excessive algae growth and dangerous temperature fluctuations.

Water Parameters

Common Goldfish are among the most adaptable freshwater fish when it comes to water chemistry, tolerating a broad range of parameters. However, they are far less tolerant of poor water quality than many keepers realise. Their high waste output means that ammonia and nitrite can build up rapidly in undersized or poorly filtered tanks, leading to stress and disease. Maintaining pristine water quality is the single most important aspect of goldfish care.

Temperature	10–24 °C
pH	6.5–8.0
General hardness (GH)	5–19 dGH
Carbonate hardness (KH)	4–12 dKH
Ammonia	0 ppm
Nitrite	0 ppm
Nitrate	Below 40 ppm

As a coldwater species, Common Goldfish do not require a heater in most indoor environments. They are comfortable at room temperature in temperate climates and can tolerate temperatures down to near freezing in outdoor ponds, provided the water does not freeze solid and sufficient oxygen exchange is maintained. In tropical climates or very warm rooms, care should be taken to ensure water temperatures do not consistently exceed 24 °C, as prolonged exposure to high temperatures can stress the fish and reduce dissolved oxygen levels.

Regular water changes are essential. A weekly water change of 25–30% is a good baseline for most setups, though tanks with higher stocking densities or less powerful filtration may require more frequent changes. Always use a reliable dechlorinator when adding tap water, and try to match the temperature of the new water to the tank water to avoid sudden thermal shocks. Test the water regularly using a liquid test kit, paying particular attention to ammonia, nitrite, and nitrate levels.

Filtration and Equipment

Filtration is arguably the most critical piece of equipment in a goldfish aquarium. Common Goldfish are messy fish that produce a significant amount of waste relative to their body size. The filter should ideally be rated for at least twice the volume of the tank. For example, a 200-litre goldfish tank should have a filter rated for 400 litres or more. This ensures adequate mechanical, biological, and chemical filtration to cope with the heavy bioload.

External canister filters are an excellent choice for goldfish aquariums, offering large media capacity, strong flow rates, and easy maintenance. Hang-on-back (HOB) filters are a more affordable alternative and work well for smaller setups or as supplementary filtration. Internal filters can be used but may struggle to keep up with the waste production of adult goldfish unless they are generously sized. Sponge filters provide excellent biological filtration and are gentle enough for fry tanks but are typically insufficient as the sole filter for adult Common Goldfish.

Adequate aeration is important, particularly in warmer weather when dissolved oxygen levels drop. An air pump with an airstone or a filter with good surface agitation will help maintain oxygen levels. Common Goldfish are active fish that consume more oxygen than many tropical species of similar size.

A heater is generally not required for Common Goldfish, but a thermometer is essential to monitor water temperature and ensure it remains within the acceptable range. In regions with very cold winters or very warm summers, a heater or aquarium chiller may occasionally be necessary to prevent extreme temperature fluctuations indoors.

Lighting should be provided via a standard aquarium LED unit. While goldfish do not have stringent lighting requirements, a consistent photoperiod helps regulate their biological rhythms. An automatic timer set for 8–10 hours of light per day is convenient and reliable. If the tank receives ambient room light, this can also contribute to the photoperiod, so adjust accordingly to avoid excessive total light exposure, which promotes nuisance algae.

Diet and Feeding

Common Goldfish are true omnivores with hearty appetites, and providing a varied, balanced diet is essential for their health, colour, and longevity. A high-quality staple food should form the foundation of the diet, supplemented regularly with a range of fresh, frozen, and live foods.

For the staple diet, choose a goldfish-specific pellet or flake food from a reputable manufacturer. Sinking pellets are often preferred over floating foods, as they reduce the amount of air goldfish gulp at the surface, which can contribute to buoyancy problems. Look for foods with a moderate protein content (around 30–40%) and a good proportion of plant-based ingredients. Avoid foods with excessive fillers or artificial colouring agents.

Fresh vegetables should be offered several times per week. Blanched peas (with the skin removed) are a classic goldfish food and help promote healthy digestion. Other excellent options include blanched spinach, lettuce, courgette (zucchini), cucumber, and small pieces of blanched broccoli. Goldfish will also graze on algae and soft-leaved aquatic plants, which is a natural and healthy behaviour.

Frozen and live foods provide valuable protein and enrichment. Bloodworms, daphnia, brine shrimp, and tubifex worms are all eagerly accepted. These foods are particularly useful for conditioning fish for breeding. Live foods also encourage natural foraging behaviours. However, these should be treated as supplements rather than dietary staples to avoid excessive protein intake.

Feed small amounts two to three times per day, offering only as much food as the fish can consume within two to three minutes. Overfeeding is one of the most common mistakes in goldfish keeping and leads to poor water quality, obesity, and digestive issues. Common Goldfish are perpetually hungry and will always appear to beg for food, but this should not be taken as an indication that they need more. A regular fasting day once per week can be beneficial for digestion.

Behaviour and Temperament

Common Goldfish are social, active, and surprisingly intelligent fish. They are naturally gregarious and do best when kept in groups of two or more, though they can be kept singly if the keeper provides adequate stimulation and interaction. In groups, goldfish exhibit a range of social behaviours, including shoaling, following each other around the tank, and establishing loose hierarchies. Aggression is rare, though mild chasing may occur, particularly during feeding or spawning periods.

These fish are diurnal, meaning they are most active during the day and rest at night. During daylight hours, they spend their time swimming actively throughout the tank, foraging through the substrate, investigating decorations, and interacting with their tank mates. Their constant activity and inquisitive nature are a large part of their appeal as aquarium fish.

Common Goldfish are remarkably intelligent for fish and can learn to recognise their keepers, respond to visual cues, and even be trained to perform simple tricks using positive reinforcement (food rewards). Many keepers report that their goldfish swim to the front of the tank when they approach and follow their movements, particularly around feeding time. This level of interactivity makes them genuinely engaging pets.

One behaviour that new keepers may find alarming is bottom-sitting or hovering motionlessly. While goldfish do rest, prolonged lethargy or bottom-sitting can be a sign of illness, poor water quality, or stress. Healthy Common Goldfish should be active and alert during the day, swimming with smooth, confident movements. Clamped fins, erratic swimming, flashing (rubbing against surfaces), or gasping at the surface are all potential indicators of health problems that warrant investigation.

It is worth reiterating that Common Goldfish are vigorous, fast swimmers. They are not suitable tank mates for slow-moving fancy goldfish varieties, which they will outcompete for food and may inadvertently stress with their boisterous activity.

Tank Mates

Choosing appropriate tank mates for Common Goldfish requires careful consideration of several factors: temperature compatibility, size, activity level, and the goldfish’s tendency to eat anything that fits in its mouth. Common Goldfish are coldwater fish, which immediately rules out most tropical species. They are also large, active, and produce heavy waste, meaning tank mates need to be robust enough to share the same environment without being bullied, outcompeted for food, or eaten. The best companions are other coldwater species of similar size and temperament.

Good tank mates

Comet Goldfish, a fellow single-tailed goldfish with the same care requirements, activity level, and temperature tolerance.
Shubunkin Goldfish, another single-tailed variety that matches the Common Goldfish in size, speed, and hardiness.
White Cloud Mountain Minnow, a small, peaceful coldwater schooling fish that thrives in similar temperatures, though best kept in groups and only with smaller goldfish.
Dojo Loach, a peaceful, coldwater-tolerant bottom dweller that coexists well with goldfish and adds interest to the lower levels of the tank.
Bristlenose Pleco, Tolerates cooler temperatures reasonably well and helps with algae control, though may occasionally attempt to latch onto goldfish in warmer conditions.
Rosy Barb, an active, colourful coldwater species that is large enough to avoid being eaten and enjoys similar temperatures.
Zebra Danio, a hardy, fast-swimming coldwater fish that can keep pace with active goldfish, best kept in a group of six or more.
Variatus Platy, one of the more cold-tolerant livebearers that can adapt to the cooler temperatures goldfish prefer.

Fish to avoid

Fancy Goldfish, Slow-moving varieties such as Orandas, Ranchus, and Telescopes cannot compete with the speed and activity of Common Goldfish and will be outcompeted for food.
Neon Tetra, far too small and requires warmer tropical temperatures; will likely be eaten by adult goldfish.
Betta, a tropical species that requires warm, still water; its long fins make it vulnerable to nipping and it cannot tolerate goldfish temperatures.
Common Pleco, Grows extremely large, produces enormous waste, and is known to latch onto and damage the slime coat of goldfish.
Tiger Barb, a notorious fin nipper that will harass goldfish, and prefers warmer water than goldfish tolerate comfortably.
Chinese Algae Eater, Becomes aggressive with age and is well known for latching onto the sides of slow-moving or large-bodied fish like goldfish.
African Cichlids, Aggressive, territorial, and require entirely different water chemistry and temperatures.
Cherry Shrimp, too small and will be readily eaten by goldfish of any size.

Breeding

Common Goldfish are among the easiest freshwater fish to breed, often spawning readily in both ponds and large aquariums with minimal intervention from the keeper. In temperate climates, breeding is typically triggered by the transition from cooler winter temperatures to the warmer conditions of spring, and this seasonal cycle can be replicated in the aquarium to encourage spawning.

To condition goldfish for breeding, gradually lower the water temperature over several weeks to around 12–14 °C, simulating winter. During this period, reduce feeding slightly. Then, over the course of one to two weeks, gradually raise the temperature to 20–22 °C while increasing feeding with high-protein foods such as bloodworms, daphnia, and brine shrimp. This temperature increase, combined with improved nutrition and increased daylight hours, triggers spawning behaviour in sexually mature fish, which are typically at least two years old.

Males in breeding condition develop white breeding tubercles (small raised bumps) on their gill covers and the leading rays of their pectoral fins. They will begin to chase females vigorously around the tank, nudging their flanks and vent area to encourage egg release. This chasing behaviour can be quite intense and may last for several hours. It is important to ensure there are no sharp decorations that could injure the fish during these vigorous pursuits.

Females scatter adhesive eggs over fine-leaved plants, spawning mops, or any available surface. A single spawning event can produce hundreds to several thousand eggs. The parents will eat the eggs and fry if given the opportunity, so eggs should be removed to a separate rearing tank or the adults should be removed from the spawning tank immediately after spawning is complete.

Eggs typically hatch within four to seven days, depending on temperature. The fry are tiny and initially feed on their yolk sac before becoming free-swimming. Once free-swimming, they can be fed infusoria, liquid fry food, or very finely crushed flake food. As they grow, they can be transitioned to baby brine shrimp and then to crushed pellets. Growth rate depends on water quality, temperature, food availability, and stocking density. Juvenile goldfish begin to develop their adult colouration at around three to six months of age, though the full colour change can take up to two years.

Common Diseases

Common Goldfish are generally hardy and resistant to disease when kept in appropriate conditions. However, poor water quality, overcrowding, inadequate diet, and temperature stress can all compromise their immune system and make them susceptible to a range of ailments.

White spot disease (Ichthyophthirius multifiliis), commonly known as ich, is one of the most frequently encountered diseases in goldfish. It presents as small white spots resembling grains of salt on the body, fins, and gills. Affected fish may flash against surfaces, clamp their fins, and become lethargic. Ich is highly treatable if caught early, typically with increased temperature (where appropriate for coldwater fish, raising to around 24 °C temporarily), salt baths, or proprietary ich medications. Maintaining stable water temperatures helps prevent outbreaks.

Fin rot is a bacterial infection that causes the edges of the fins to become ragged, discoloured, and progressively eroded. It is almost always secondary to poor water quality or physical injury. Treatment involves improving water conditions through water changes and, in severe cases, antibacterial medications. If caught early, fin regrowth is usually complete.

Swim bladder disorder is common in goldfish and manifests as buoyancy problems, the fish may float uncontrollably at the surface, sink to the bottom, or swim at an abnormal angle. In Common Goldfish, this is less frequent than in fancy varieties due to their natural body shape, but it can still occur. Causes include overfeeding, constipation, bacterial infection, or, rarely, anatomical abnormalities. Fasting the fish for 24–48 hours and then offering blanched, deshelled peas often resolves cases caused by digestive issues.

Dropsy is a serious condition characterised by severe bloating and raised, pinecone-like scales. It is typically a symptom of internal organ failure, often caused by bacterial infection. Dropsy is difficult to treat, and the prognosis is unfortunately poor in many cases. Isolation, antibacterial medication, and Epsom salt baths may help in early stages, but prevention through excellent water quality and nutrition is the best approach.

Anchor worm and fish lice are external parasites that may occasionally affect goldfish, particularly those kept in outdoor ponds or introduced from infested sources. These parasites are visible to the naked eye and can be removed manually or treated with appropriate antiparasitic medications. Quarantining all new fish before adding them to an established tank or pond is the most effective preventive measure.

Fungal infections appear as cotton-wool-like growths on the body, fins, or mouth. They are typically secondary infections that take hold on damaged tissue or in fish with compromised immune systems. Antifungal medications are effective, but addressing the underlying cause, usually poor water quality or injury, is essential for long-term resolution.

FAQs

Can Common Goldfish live in a bowl?

No. Common Goldfish should never be kept in a bowl. They are large, active fish that can grow to over 30 cm and live for decades. A bowl cannot provide adequate space, filtration, or oxygen exchange for their needs. The absolute minimum tank size for a single Common Goldfish is 150 litres, and larger is always better. Keeping a goldfish in a bowl leads to stunted growth, chronic stress, poor water quality, and a dramatically shortened lifespan.

How big do Common Goldfish actually get?

In a suitably large aquarium, Common Goldfish typically reach 20 to 35 cm (8 to 14 inches) in body length. In outdoor ponds with abundant space and food, they can occasionally exceed this. Their growth rate is influenced by tank size, water quality, diet, and genetics. Even in smaller tanks, goldfish continue to grow internally even if their external growth appears stunted, which causes organ compression and serious health problems.

Can Common Goldfish live with tropical fish?

Generally, no. Common Goldfish are coldwater fish that prefer temperatures between 10 and 24 °C, which is too cool for most tropical species. Keeping goldfish in heated tropical tanks can shorten their lifespan by increasing their metabolic rate beyond what is natural. Additionally, goldfish produce far more waste than most tropical fish of comparable size, which can overwhelm the filtration in a typical tropical community tank. The best tank mates are other coldwater species with similar care requirements.

How often should I feed my Common Goldfish?

Feed small amounts two to three times per day, offering only as much food as the fish can consume within two to three minutes per feeding session. Overfeeding is a very common mistake and leads to obesity, digestive problems, and dangerously poor water quality. A weekly fasting day is beneficial for digestion. Vary the diet with quality pellets, blanched vegetables, and occasional frozen or live foods for optimal health and colour.

Do Common Goldfish need a heater?

In most indoor environments in temperate climates, Common Goldfish do not require a heater. They are comfortable at typical room temperatures and can tolerate a wide range from 10 to 24 °C. However, they do need stable temperatures, sudden or extreme fluctuations can cause stress and illness. In very cold rooms during winter or in regions with extreme temperature swings, a low-wattage heater set to a minimum temperature of around 14–16 °C can provide stability. A thermometer should always be used to monitor the water temperature.

Comet Goldfish, a closely related single-tailed goldfish variety with longer finnage that shares identical care requirements.
Shubunkin Goldfish, another single-tailed goldfish variety with striking calico colouration, ideal for keeping alongside Common Goldfish.
Fancy Goldfish, an overview of the many double-tailed goldfish varieties and how their care differs from single-tailed types.
Dojo Loach, a popular coldwater companion for goldfish that thrives in the same temperature range and tank conditions.
White Cloud Mountain Minnow, a small, hardy coldwater schooling fish often recommended as a goldfish tank mate for larger setups.