Why goldfish aren't starter fish

The goldfish is the fish nearly everyone meets first, and the one most often kept badly. It is sold in bowls and tiny "starter" kits, beside the promise that it is the easiest pet in the shop. The truth is almost the opposite. A goldfish is a large, long-lived, cold-water fish that produces a heavy load of waste, and those three facts, cold water, size, and bioload, are exactly why it is not a beginner's fish. This guide explains what a goldfish really needs, and how to keep one well if you want to.

Published 30 June 2026 · Last updated 30 June 2026 · 12 min read

Why goldfish aren't starter fish

Goldfish are cheap, sold everywhere, and handed out as fairground prizes, so they have a reputation as the throwaway beginner fish: drop one in a bowl, feed it a flake a day, and that is goldfish keeping. Almost everything about that picture is wrong, and it is why so many goldfish die within months of being brought home.

The problem is not that goldfish are delicate. They are genuinely hardy, which is the trap: a goldfish will survive poor conditions for a surprisingly long time before they catch up with it. Hardy is not the same as low-maintenance. A goldfish has three requirements that a starter setup never provides:

• Cool water. They are cold-water fish, not tropical ones, which rules out the heated community tank they are usually sold alongside.
• Space, and a lot of it. They grow large and live for years, so a single fish needs more water than most people expect, and a bowl is out of the question.
• Heavy-duty filtration. They eat and excrete far more than a small tropical fish, so they foul water fast and need filtration and water changes to match.

Meet those three and a goldfish is a hardy, interactive, long-lived pet that will outlast a dog. Miss them and it is a slow decline. That is why the hobby files goldfish under intermediate, not beginner: not because they are fragile, but because the setup they actually need is bigger than the one they are sold with.

Fancy and common goldfish are not the same fish

Before anything else, work out which goldfish you have, because two very different fish are sold under the one name and they need different homes.

Single-tailed goldfish, the common goldfish, comets, and shubunkins, are the slim, fast, torpedo-shaped fish. They reach 25 to 30 cm, swim powerfully, and are really pond fish. In a tank they are almost always under-housed. If you have one of these, think pond, not aquarium.

Fancy goldfish, the round-bodied fantails, orandas, ryukins, telescopes, and their kin, are the egg-shaped, slow, double-tailed fish. They stay nearer 15 to 20 cm, swim less strongly, and are the type that can reasonably live in a large aquarium. Their rounded body makes them slower and more prone to swim bladder trouble, so they suit calm water and careful feeding.

Do not mix the two types. A fast single-tailed common will out-compete and out-swim a slow fancy at feeding time, and the fancy goes hungry. Keep fancies with fancies, and commons with commons (or in a pond).

Goldfish are cold-water fish

This is the fact that surprises most people: a goldfish is a cold-water fish. It is comfortable from about 10 to 24°C, and does best in the cool middle of that range, around 18 to 22°C. In most Australian homes that is simply room temperature, which means a goldfish needs no heater at all.

This is also why goldfish cannot live in a tropical community tank. The tetras, guppies, and other small fish they are so often paired with need 24 to 26°C, while a goldfish wants water several degrees cooler. One of them is always uncomfortable, and the temperature mismatch alone makes the pairing a poor idea, before you even get to the size and waste differences. Goldfish belong with other cool-water fish, or on their own.

The space a goldfish really needs

Goldfish grow large and live for a decade or two, so they need far more water than their price tag suggests. As a starting point, a pair of fancy goldfish needs at least 150 litres, with roughly another 50 litres for each additional fish. Single-tailed commons and comets need more again, 200 litres at an absolute minimum, and are happier in a pond. Keep at least two: goldfish are social and settle better in company.

Work out the true volume of any tank with the tank volume calculator rather than trusting the figure on the box, and sanity-check your stocking with the stocking calculator. A "starter" tank of 20 to 60 litres is not a goldfish tank, and the classic bowl is not a tank at all.

This is the single biggest reason goldfish die. A fish that should live 15 years and reach the size of your hand is kept in a few litres, stunts, and is gone in a year or two, which then reinforces the idea that goldfish are short-lived and disposable. They are not. Given the room, they are one of the longest-lived fish you can keep.

The bioload problem

Goldfish are big eaters and big waste producers. They graze more or less constantly, lack a true stomach, and pass a heavy stream of waste, all of which becomes ammonia in the water. That waste output, the bioload, is high for the fish's size, and it is the third reason a small tank fails them: the water fouls faster than a beginner setup can cope with.

Two things keep up with it:

• Oversized filtration. Run a filter rated well above your tank's volume, ideally for a tank larger than the one you have. Goldfish suit a strong canister or a generous hang-on-back filter packed with biological media. Our filter guide covers sizing and media.
• Generous water changes. The standard 25% weekly change is a floor for goldfish, not a ceiling. A well-stocked goldfish tank often needs a larger or more frequent change to keep nitrate down. See the water changes guide.

As with any tank, cycle it before the fish move in so the filter can process that ammonia from day one; never use a goldfish to cycle a tank. Our cycling guide walks through the fishless method. If you plan a goldfish community, the stocking guide explains how to budget the bioload.

Keeping goldfish properly

None of this is hard once the tank is the right size. A good goldfish setup is a large, strongly filtered, unheated tank, kept clean. A few specifics make it a good goldfish home rather than just a big tank.

Smooth surfaces and the right substrate. Goldfish root through the substrate and can get small gravel stuck in their mouths. Use sand or large, smooth pebbles too big to swallow, and avoid sharp decor and hard plastic plants, especially for telescope and bubble-eye fancies whose eyes are easily injured. The substrate guide covers the options.

A sensible diet. Goldfish are omnivores, not the flake-only fish they are treated as. Feed a quality sinking goldfish pellet or gel food (brands like Hikari, New Life Spectrum, and Repashy), with blanched vegetables and the occasional frozen treat. For round-bodied fancies, soak or use sinking food rather than dry floating pellets, which make them gulp air and aggravate swim bladder problems. Feed small amounts they finish in a minute or two, and never overfeed: in a heavy-bioload tank, leftover food is the fastest route to bad water. The feeding guide has the full method.

The right tankmates, which usually means other goldfish. The simplest, safest goldfish tank is goldfish only, matched by type. If you want company for them, stay with cool-water species of similar temperament: white cloud mountain minnows and rosy barbs are temperate fish that share a goldfish's temperature range, though even these need a large tank and can be nipped or, when small, eaten. Avoid tropical community fish (the temperature is wrong), and avoid shrimp and tiny fish, which a goldfish treats as food.

Goldfish in Australia

Goldfish are sold in every aquarium and pet shop in the country, and a backyard pond suits them beautifully across much of the Australian climate. A pond solves the space and temperature problem at a stroke, and is arguably the ideal goldfish home: it gives single-tailed commons and comets the room they need and keeps fancies cool through summer if it is deep and shaded.

On water chemistry, goldfish are easy here. They suit a pH of about 7.0 to 8.4 and hard, alkaline water, so the naturally hard tap water of Brisbane, the Gold Coast, Adelaide, and Perth suits them with no adjustment, and the softer water of Melbourne and Sydney is fine too. All they need from tap water is a dechlorinator that handles chloramine, such as Seachem Prime. Any pump or filter should be Australian-certified 240 V equipment, not an uncertified import, though remember a goldfish needs no heater.

See the goldfish care sheets for the data at a glance, and our guides on choosing your first fish, stocking a community tank, and cycling a new aquarium, or browse the species directory.