Comet Goldfish
The Comet is the athletic goldfish - a slim, single-tailed American breed with a long flowing tail that streams behind it like its namesake.
🗓️ Last reviewed: July 2026
Overview
The Comet is the athletic goldfish - a slim, single-tailed American breed with a long flowing tail that streams behind it like its namesake. Fast, hardy and eventually large, it is a pond fish first and a tank fish only in the biggest aquariums; the classic 'feeder fish' grows into a 30 cm beauty given the space it deserves.
Natural History
Developed in 1880s America from common goldfish stock, selected for the elongated deeply forked tail; the first distinctly American goldfish breed.
Appearance
Slim-bodied and streamlined, reaching 25-30 cm in ponds; the tail can be nearly as long as the body. Classic orange, plus red-and-white (the prized Sarasa pattern), yellow and white.
Tank Size & Setup
Honestly: a pond, or an aquarium of 200+ liters for a pair - Comets are fast, big and messy. Cool, well-filtered, well-oxygenated water and open swimming length matter more than decor. Fine for ponds year-round in temperate climates.
Water Parameters
Cold-water: 10-24°C, no heater; strong filtration (goldfish are waste machines), regular big water changes, pH 7.0-8.0. They tolerate a wide range but not poor maintenance.
Diet
Quality goldfish pellets or gel food as the staple, plus blanched greens, peas and occasional live/frozen treats. Feed sparingly - their enthusiasm outstrips their needs.
Health & Lifespan
Average lifespan is 10-20 years. Among the toughest of all fancy fish: 10-20 years is routine, 25+ recorded in good ponds. Main risks are stunting in small tanks, poor water from overstocking, and swim-bladder trouble from overfeeding.
Pros & Cons
Pros
- Extremely hardy and long-lived
- Beautiful flowing single tail
- Perfect beginner pond fish
- Inexpensive and available everywhere
Cons
- Far too big and active for small tanks
- Messy - demands serious filtration
- Outgrows promises made at the pet store
- Eats pond plants happily
Comet Goldfish - frequently asked questions
Can a Comet live in a bowl or small tank?
No - this is a 25-30 cm athletic fish. A bowl stunts and kills it slowly; a pond or very large tank lets it become what it actually is.
What's a Sarasa Comet?
The red-and-white patterned form - bright crimson patches on white, pond-visible from across the garden and highly sought after.
Do Comets survive winter outdoors?
In a pond at least 60-90 cm deep that doesn't freeze solid, yes - they slow down and overwinter on the bottom like koi.
🧠 Test yourself: guess the fish
Three clues from our quiz bank, each about another of our fish. Can you name them?
Clue 1.Prized for vivid stripes and patterns, this disc-shaped fish is one of the most colorful freshwater species kept.
It's the Discus - read the full profile →
Clue 2.Contrary to popular myth, this hardy pet has a memory spanning months and should never be kept in a tiny bowl.
It's the Goldfish - read the full profile →
Clue 3.This tiny, hardy aquarium fish gives birth to live young rather than laying eggs, earning it the nickname 'rainbow fish.'
It's the Guppy - read the full profile →