Comet Goldfish 5cm – Assorted Colours

The Comet Goldfish is a hardy, active single-tail goldfish with a streamlined body and long, forked tail.

At approximately 5cm, these are young fish with plenty of growing to do. Adult Comets commonly reach around 25–30cm, so their long-term space requirements should be considered before purchase.

This listing is for assorted colours. Individual fish may display different combinations of orange, red, gold, yellow, white and other natural goldfish tones. Colour and markings cannot be guaranteed unless a specific variety is listed separately.

Quick Care Guide

• Scientific Name: Carassius auratus
• Common Name: Comet Goldfish
• Sale Size: Approximately 5cm
• Adult Size: Commonly around 25–30cm
• Temperament: Peaceful, active
• Water Type: Freshwater / coldwater to temperate
• Temperature: Approximately 10–24°C
• pH: Approximately 6.5–8.0
• Water Hardness: Approximately 5–19 dGH
• Diet: Omnivore
• Care Level: Easy, provided adequate space and filtration are available
• Breeding: Egg scatterer
• Sex: Unsexed
• Suitable For: Large filtered aquariums and outdoor ponds

Not a Small Goldfish

Comet Goldfish are often sold when they are only a few centimetres long, but they should not be selected based on their current size.

These are large, fast-swimming goldfish that can grow to around 25–30cm and produce a substantial amount of waste.

For long-term indoor keeping, provide a large, well-filtered aquarium around 120cm in length or larger. Around 200 litres should be considered a starting point for long-term housing, with significantly more space required for multiple adult Comets.

Outdoor ponds are an excellent long-term option where climate, pond design and local conditions are suitable.

Why Comet Goldfish Need Good Filtration

Goldfish are active feeders and produce considerably more waste than many similarly sized tropical aquarium fish.

A suitable Comet setup should include:

• strong biological filtration
• good water movement and oxygenation
• plenty of open swimming space
• regular partial water changes
• a fully cycled aquarium or pond

Ammonia and nitrite should remain at zero, with nitrate controlled through filtration, appropriate stocking and regular maintenance.

Aquarium Setup

Comets are strong, active swimmers and appreciate an aquarium with plenty of open space.

A practical setup can include:

• smooth gravel or sand
• rounded rocks and décor
• hardy aquarium plants
• large open swimming areas
• strong filtration
• good surface movement and oxygenation

Avoid sharp décor that could damage the fish as they move quickly around the aquarium.

Goldfish may dig through substrate and uproot or eat softer aquarium plants, so plant choice and positioning should take this behaviour into account.

Water Conditions

Comet Goldfish tolerate a fairly broad range of water conditions, but clean and stable water remains essential.

For normal aquarium keeping, aim for approximately:

• Temperature: 10–24°C
• pH: 6.5–8.0
• General Hardness: 5–19 dGH

Comets usually do not require a heater in typical indoor Australian conditions unless room temperatures fall outside an appropriate range.

Avoid sudden changes in temperature or water chemistry when moving fish between aquariums or ponds.

Comet Goldfish in Outdoor Ponds

Comets are particularly well suited to outdoor ponds because their streamlined body, strong swimming ability and eventual adult size make excellent use of larger water volumes.

A suitable pond should provide:

• adequate depth and swimming space
• good oxygenation
• appropriate filtration
• some shade or shelter
• protection from predators where necessary

Always make sure the pond is suitable for the adult number and size of fish rather than stocking according to their juvenile sale size.

Tank Mates

Comet Goldfish are generally peaceful and work best with other compatible single-tail goldfish that have similar swimming ability and feeding behaviour.

Suitable companions can include other appropriately sized:

• Comet Goldfish
• Shubunkins
• Common Goldfish
• other robust coldwater fish where their care requirements are compatible

Comets are fast feeders and can out-compete slower fancy goldfish such as Orandas, Ranchu and some Fantails for food. For this reason, mixing fast single-tail goldfish with slow fancy varieties is generally best avoided.

Very small fish may eventually be eaten if they fit into an adult goldfish's mouth.

Feeding Comet Goldfish

Comet Goldfish are omnivorous and benefit from a varied diet formulated specifically for goldfish.

A balanced feeding routine can include:

• quality goldfish pellets
• goldfish flakes
• vegetable-based foods
• occasional suitable frozen foods
• blanched vegetables as part of a varied diet

Feed controlled portions rather than large amounts at once. Excess food quickly contributes to poor water quality in a goldfish aquarium.

Assorted Colours

Comet Goldfish occur in a wide range of colours and patterns.

Fish supplied from this listing may include different combinations of:

• orange
• red
• gold or yellow
• white
• mixed or patterned colouration

Colour and markings can continue to change as young goldfish mature.

Product photographs should be considered representative only. If you require a particular colour or pattern, choose a product specifically listed for that variety where available.

Comet Goldfish vs Fancy Goldfish

Comets have a streamlined body and a single forked tail. They are generally faster, stronger swimmers than rounded fancy goldfish varieties.

Fancy goldfish such as Orandas, Ranchu and Black Moors have been selectively bred for different body shapes and fins and usually swim more slowly.

This difference is important when choosing tank mates because fast Comets can reach food before slower fancy goldfish.

Browse our Goldfish range to compare other available varieties.

Are Comet Goldfish Suitable for Beginners?

Yes, provided the aquarium or pond is large enough.

Comets are hardy fish, but their large adult size and high waste production mean that successful care depends on providing plenty of water volume, strong filtration and regular maintenance.

A small bowl is not an appropriate long-term home for a Comet Goldfish.

Arrive Alive Guarantee

We carefully pack our live fish for transport and back eligible orders with our Arrive Alive Guarantee.

If a fish arrives deceased, please contact us within 2 hours of delivery with your order details and clear photos of the affected fish. Once the claim has been verified, an applicable refund or store credit will be provided for the affected fish.

For full claim requirements, shipping conditions and exclusions, please read our Arrive Alive Guarantee & DOA Policy.

Frequently Asked Questions

How big do Comet Goldfish grow?

Comet Goldfish commonly reach around 25–30cm when mature and can potentially grow larger under excellent conditions. The fish offered here are approximately 5cm juveniles.

Can Comet Goldfish live in a bowl?

No. Comets are large, active fish that need substantial swimming space, strong filtration and good oxygenation. A properly sized aquarium or pond is required.

Do Comet Goldfish need a heater?

Usually not. Comets are coldwater to temperate fish and generally cope well with normal indoor temperatures, provided sudden temperature changes are avoided.

Can Comet Goldfish live in a pond?

Yes. Comets are particularly well suited to appropriately designed outdoor ponds with adequate space, filtration, oxygenation and protection.

Can Comets live with fancy goldfish?

It is generally better to keep fast single-tail goldfish such as Comets with fish of similar swimming ability. Comets can easily out-compete slower fancy goldfish for food.

What colours will I receive?

This is an assorted-colour listing, so individual fish may vary in colour and pattern. Product photographs are representative and a particular colour cannot be guaranteed.

Are Comet Goldfish good beginner fish?

Yes, provided their adult size and filtration requirements are properly planned for. Their hardiness does not make them suitable for small bowls or undersized aquariums.

How long do Comet Goldfish live?

Goldfish are long-lived fish and can live for well over 10 years when provided with appropriate space, nutrition and water quality.

Live fish naturally vary in colour, markings, finnage and size. The stated 5cm sale size is approximate and product photos should be considered representative of the assorted colour range.