How to choose your first fish

What makes a fish genuinely beginner-friendly, the common species to avoid, and concrete recommendations by tank size and water type.

Published 6 June 2026 · Last updated 18 June 2026 · 13 min read

Before you choose fish, choose a tank

The most common mistake in fishkeeping is choosing the fish first and the tank second. It is how people end up with goldfish in 20-litre tanks, common plecos in community setups, and angelfish in everything. The right order is:

1. Decide on a tank size you will actually keep clean. A 75-litre tank is easier to maintain than a 20-litre one, which is the opposite of what most beginners expect. More water is more stable, more forgiving of mistakes, and opens up better species options.
2. Cycle the tank fully before buying any fish. See our cycling guide for the full detail. This step is not optional.
3. Test your tap water for pH, hardness, and any nitrate. This decides which species will actually thrive rather than just survive.
4. Then choose species suited to your tank size, your water, and your patience level.

What makes a fish beginner-friendly

Pet shops use "beginner-friendly" loosely. The criteria actually worth caring about are:

Hardiness in normal tap water. A genuinely beginner fish copes with the pH, hardness, and small temperature changes of an ordinary household tank without getting sick. Soft-water specialists like discus or wild bettas do not qualify, however often they are sold to first-timers.

A reasonable adult size. A fish that is "small at the shop" but grows to 30 cm is not beginner-friendly. The fish you bring home will reach its adult size eventually, and your tank has to support that. Goldfish and common plecos are the classic examples of this trap.

A peaceful temperament. Aggressive, territorial, or fin-nipping fish need more careful tankmate planning than most beginners can manage. A peaceful fish pairs with most other peaceful fish; an aggressive one rules out half your options.

Tolerance of small mistakes. Some fish shrug off the mild ammonia and nitrite slips that beginners inevitably make. Livebearers and most peaceful community fish are forgiving this way. Sensitive species like neon tetras and shrimp are not.

Room to grow into the hobby. A good first fish should let you build a normal community tank later without boxing you in. A betta locks you into a single-fish setup; a school of corydoras opens the door to dozens of compatible tankmates.

Easy to find, with known care. A species you can buy at any aquarium shop, with well-documented care, beats a rare or trendy one with patchy information. Stick to the staples for your first tank.

Species and patterns to avoid

The honest list of beginner mistakes the hobby keeps repeating:

Goldfish in tanks under 200 litres

Goldfish are sold as starter fish, and they should not be. Common goldfish reach 30 cm and live 15 years or more; fancy goldfish reach 20 cm. Both produce huge amounts of waste and need cool water (under 22°C). A goldfish in a 20-litre tank is a goldfish slowly dying. If you genuinely want goldfish, plan a 200 L or larger unheated tank, not a "starter" setup.

Common plecos sold as "algae cleaners"

The fish sold simply as "plecos" at chain pet shops are almost always common plecos (Hypostomus plecostomus), which reach 60 cm and need tanks of 750 litres or more. They are catfish, not algae cleaners. If you want a hardworking algae eater for a normal community tank, look for a bristlenose pleco instead. It stays around 12 cm and is genuinely beginner-friendly.

Bettas crammed into "betta cubes"

The 1 to 2 litre cube tanks sold for bettas are inhumane, regardless of the marketing. A betta needs at least 30 litres, with a heater and a gentle filter. It is a wonderful first fish, in a properly sized tank.

"Cycling" with hardy fish

Some pet shops still suggest adding a couple of "hardy fish" to a new tank to "cycle it." This kills fish slowly while the cycle establishes. Fishless cycling is the correct approach. Do not add fish until your tank is fully cycled.

Bala sharks, redtail sharks, iridescent sharks

All grow far larger than their juvenile shop sizes suggest. Bala sharks reach 35 cm; iridescent sharks reach 1 metre and are catfish, not sharks. None are suitable for a typical home aquarium.

Single specimens of schooling fish

Many beginner fish (tetras, rasboras, corydoras) are schooling species that need groups of six or more to behave naturally. Pet shops will happily sell you two neon tetras. Do not accept that. Either commit to a proper school or choose a fish that is happy alone.

Aggressive cichlids in a community tank

African and South American cichlids are stunning, but they are not community fish. Beginners often impulse-buy "that pretty blue fish" without realising it is a 25 cm aggressive cichlid that will systematically kill everything else in the tank.

Know your tap water first

Your tap water decides what will thrive versus what will struggle. After tank size, the biggest beginner mistake is fighting your local water chemistry instead of working with it.

See our water parameters guide for the full detail on each region, and our best freshwater fish for Australian tap water guide for species picks by region. As a quick reference for Australian fishkeepers:

• Hard, alkaline water (Brisbane, Gold Coast, Adelaide, Perth): ideal for livebearers (guppies, platies, mollies), snails, and most community fish. Avoid soft-water specialists like neon tetras and shrimp unless you remineralise.
• Moderate water (Sydney): the most flexible. Most community species work.
• Soft water (Melbourne): excellent for tetras and discus, harder for livebearers and snails without supplementation.

Recommended starter fish by tank size and water type

The species below are all genuinely beginner-friendly: hardy, well documented, peaceful, and widely available in Australia. Click any species name for our detailed care guide.

Each of these combinations is genuinely beginner-friendly, given the matching tank size and water type. None needs advanced technique to keep alive. Before you buy, our stocking calculator can check that your chosen mix fits your tank's size and water.

Building a balanced community

A good community tank uses the whole space. The top, middle, and bottom of the tank are different habitats, and fish that occupy different levels make better use of the room and look more interesting.

Top-dwellers: livebearers (guppies, platies, mollies), gouramis, hatchetfish.

Middle-dwellers: most tetras and rasboras, dwarf cichlids, danios.

Bottom-dwellers: corydoras, kuhli loaches, otocinclus, bristlenose plecos.

A well-balanced community has at least one species at each level. A tank stocked entirely with mid-water tetras looks empty top and bottom; adding a small school of corydoras and a single bristlenose pleco fills it out properly.

Keep schooling species in genuine schools: six at the absolute minimum, ideally eight to ten. A school of ten neon tetras shows behaviour and colour you will never see in a group of three.

Stocking timeline: when to add what

Even with a fully cycled tank, do not add all your fish on day one. The bacteria colony in your filter is sized for the ammonia load you used to cycle the tank. Adding twenty fish at once produces more waste than the colony can handle, which triggers a mini-cycle and an ammonia spike.

A realistic stocking pace:

• Week 1: add roughly a third of your intended stock, usually your first school or main centrepiece fish.
• Test daily for two weeks after each addition. If ammonia or nitrite become detectable, do a large water change and wait longer before adding more.
• Week 3: add the next third, such as the bottom-dwellers or a second species.
• Week 5: add the final third.

This pace means your tank takes 5 to 6 weeks to become fully stocked from a finished cycle. It feels slow, but it is the timeline that produces stable, healthy tanks rather than crashes.

Buying healthy fish from the shop

The fish you bring home is only as healthy as the shop you bought it from. A few things to check before handing over money:

Look at the whole tank, not just your target fish. Are there dead or dying fish in the same tank? Even one floating fish suggests the others have been exposed to whatever killed it. Walk away.

Watch the fish swim before buying. Healthy fish are active, alert, and have clean fins. Avoid any fish that hides constantly, lists to one side, has clamped fins, has white spots (ich), or has visibly damaged fins.

Ask how long the fish has been in the shop. Fish fresh from a wholesaler are stressed and prone to disease. Fish that have been in the shop for two weeks or more with no visible problems are a much safer buy.

Be willing to leave empty-handed. The pressure to "buy something while you are there" is real but worth resisting. A bad fish at your favourite shop is still a bad fish.

If you have not set up your tank yet, start with how to set up a new aquarium. Once you have chosen your fish, see our guides on cycling a new tank, water parameters, and water changes. For individual species' care requirements, browse our species directory.