Comet goldfish

Behaviour and habits

The comet goldfish is the fast, single-tailed, streamlined goldfish, hardier and more athletic than the fancy types and often kept in ponds. It is peaceful and greedy, swimming constantly and growing large — up to 30 cm — so it needs a big tank or pond rather than a bowl. It is very cold-hardy, tolerates cooler water than fancies, and is one of the easiest large fish to keep well.

What to feed, and how often

Sinking goldfish pellets plus blanched peas and greens, given two or three small meals a day. Feed a sinking, green-rich diet, avoid overfeeding, and remember that a big fish produces a lot of waste.

Water changes and maintenance

Change 30–50% weekly. Comets are big, messy and long-lived, so they need a large tank or pond, cold water and strong filtration to keep nitrate down.

Care and how easy it is

Not a bowl fish: it needs 150 litres or more per fish, cold water and heavy filtration, and it grows very large.

Common health problems

Hardy, but prone to fin rot and bacterial infections from poor water and overcrowding.

If it gets sick

Keep the water clean and cold, feed wholesome food, and treat early if fins become ragged or the fish goes off its food.