Comet Goldfish Care Guide
The comet goldfish (Carassius auratus) is a fast-swimming and hardy coldwater fish popular in the UK. Known for its long, flowing tail and streamlined body, it's commonly kept in ponds and large aquariums.
In this guide, you'll learn everything you need to know about comet goldfish care, including tank and pond size, water conditions, compatibility, feeding, and typical UK prices - plus how to buy or sell them locally.
Quick facts about Comet Goldfish
Comet goldfish are a single-tailed variety of goldfish, closely related to the common goldfish but with longer fins and a more streamlined appearance.
They are active swimmers and grow large, making them best suited to ponds or spacious tanks.
Carassius auratus
25-30 cm (can grow larger in ponds)
Domesticated (derived from East Asian carp)
120L+ (single fish), pond preferred long-term
10-20+ years
Peaceful, very active
4-24°C (coldwater species)
Omnivore (pellets, flakes, vegetables, live foods)
6.5-8.0
£2-£8 per fish
How Many Comet Goldfish Should You Keep?
Comet goldfish are social and do best with companions.
- Keep at least 2 where possible
- Stocking should match tank or pond size
- Provide plenty of swimming space due to their active nature
Overstocking can lead to:
- Poor water quality
- Stunted growth
- Increased disease risk
Due to their size and activity level, ponds are often the best long-term option.
Ideal Tank or Pond Conditions for Comet Goldfish
Providing the right environment is essential for their health and growth.
- Tank Setup: Large aquariums with open swimming space
- Pond Setup: Outdoor ponds are ideal for adult fish
- Substrate: Sand or smooth gravel works well
- Plants & Decor: Hardy plants with plenty of open space
- Water Conditions: Stable, well-oxygenated water
- Filtration: Strong filtration is essential due to high waste output
- Lighting: Natural or moderate artificial lighting
Regular maintenance is key to keeping water clean.
Compatibility with Other Fish
Comet goldfish are peaceful but require suitable tankmates.
- Good Tankmates: other comet goldfish, common goldfish, and similar coldwater species
- Avoid: tropical fish, fancy goldfish (too slow), and very small fish
Their speed and appetite can outcompete slower fish.
Are Comet Goldfish Easy to Care For?
Comet goldfish are easy to care for but require more space than many people expect.
They require:
- Large tanks or ponds
- Strong filtration
- Regular water changes
- A varied diet
They are hardy, but poor conditions can still lead to health issues.
Comet Goldfish Price in the UK
In the UK, comet goldfish typically cost between £2-£8 per fish.
Prices vary depending on:
- Size and colour
- Quality and fin length
- Shop vs hobbyist sellers
They are widely available and affordable.
Where to Buy Comet Goldfish in the UK
Comet goldfish are widely available in UK aquarium shops, garden centres, and from private sellers.
Sourcing fish locally can:
- Reduce transport stress
- Improve survival rates
- Offer better value
TankMate UK helps connect fishkeepers and pond keepers who want to buy, sell, or rehome fish safely - without shipping.
Can You Sell Comet Goldfish?
Yes - comet goldfish are commonly rehomed, especially when they outgrow smaller tanks.
Selling locally is often the best option, as it:
- Minimises stress for the fish
- Avoids the risks of transport
- Helps find suitable long-term homes
TankMate UK allows you to list fish quickly and find local buyers.
Feeding Comet Goldfish
Comet goldfish are omnivorous and require a balanced diet.
Key Tips:
- Feed high-quality goldfish pellets or flakes
- Supplement with vegetables such as peas and spinach
- Offer occasional live or frozen foods
- Avoid overfeeding
Common Problems with Comet Goldfish
Stunted growth, often caused by:
- Tanks that are too small
- Poor water quality
Poor water quality, due to:
- Overfeeding
- Inadequate filtration
Competition for food, caused by:
- Mixing with slower fish
Why Comet Goldfish Are So Popular
- Hardy and adaptable
- Active and engaging behaviour
- Suitable for ponds and large aquariums
- Long flowing fins
- Affordable and widely available
When kept correctly, comet goldfish are lively, impressive fish that thrive in spacious environments.
Frequently Asked Questions
They typically grow to 25-30 cm, and can grow larger in ponds.
Yes, but only in large tanks-ponds are better long-term.
No, they are coldwater fish.
At least 120 litres for one fish, with much larger setups recommended.
Looking to Buy or Sell Comet Goldfish Locally?
TankMate UK connects fishkeepers and pond keepers who want to buy, sell, or rehome fish safely within their local area.
Whether you're stocking your tank or pond or passing fish on to a new home, you can:
- Browse fish available near you
- List your own fish in minutes
- Avoid the risks of transport