Comet Goldfish

Carassius auratus

Also known as: Comet, Sarasa comet, Comet-tailed goldfish

Water Parameters

• Temperature: 10–24°C
• pH: 7–8.4
• Hardness (GH): 89–357 ppm (5–20 dGH)

Values above are general hardness (GH). For carbonate hardness (KH), the buffer that keeps pH stable, see the water parameters guide.

Care Summary

The most common single-tailed goldfish in the trade, distinguished from the plain common by a long, deeply-forked, flowing tail that can be as long as the body. Comets are lean, fast, tireless swimmers, hardy and cold-tolerant, and they reach 25 to 30cm and live for many years, which makes the fishbowl they are so often sold for a slow tragedy. They belong in a pond or a large aquarium with strong filtration and other single-tailed goldfish. In colour they range from the standard orange through the red-and-white 'Sarasa comet', a particularly popular pond form. Active, personable, and genuinely long-lived when housed properly, the comet is an excellent temperate pond fish, and one to keep strictly contained and never release into Australian waterways.

Tankmates

A single-tailed goldfish, and the same rule applies as for the common: keep comets with other single-tails (commons, shubunkins) and never with the slow, round-bodied fancies, which they outswim and outfeed to the point of starvation. Comets are, if anything, even faster and more energetic than commons, so they need length to swim and are a poor match for anything small or slow. Small fish and shrimp are eaten or outcompeted. They suit a temperate outdoor pond or a very large aquarium, and, as with all goldfish in Australia, must never be released into waterways.

Compatible with

• Common Goldfish
• Shubunkin

Avoid keeping with

• Fantail Goldfish
• Ryukin
• Oranda
• Black Moor
• Bubble Eye
• Cherry Shrimp
• Betta
• Tropical Warm Water Species

Common Problems

• outgrowing small tanks and bowls (reaches 25-30cm)
• needing length to swim as a fast, active fish
• being kept with slow fancy goldfish it outcompetes
• heavy bioload demanding strong filtration

Sources: seriouslyfish.com, fishbase.org · Last updated: 2026-06-20