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 6 June 2026 · 13 min read

Before you choose fish, choose a tank

The single most common mistake in fishkeeping is choosing the fish first and the tank second. It's 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'll actually keep clean. A 75-litre tank is easier to maintain than a 20-litre tank, contrary to beginner intuition. Larger volumes are more chemically stable, more forgiving of mistakes, and offer better species options.
2. Cycle the tank fully before buying any fish. See our cycling guide for full detail. This step is non-negotiable.
3. Test your tap water for pH, hardness, and any nitrate. This determines which species will actually thrive rather than just survive.
4. Then choose species suited to your tank size, water, and patience level.

If you've already bought a tank but haven't cycled it yet, you're at step 2. Don't skip ahead. This guide assumes you have a cycled tank ready for fish.

What makes a fish beginner-friendly

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

Hardiness in typical tap water. A genuinely beginner species tolerates the pH, hardness, and temperature swings of a normal household tank without becoming sick. Soft-water specialists like discus or wild bettas don't qualify, regardless of how often they're sold to first-time keepers.

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

Peaceful temperament. Aggressive, territorial, or fin-nipping species require more careful tankmate selection than beginners can usually navigate. A peaceful species can be paired with most other peaceful species; an aggressive species rules out half your options.

Tolerant of stocking and cycling mistakes. Some species are more resilient to mild ammonia and nitrite exposure during the inevitable beginner mistakes. Livebearers and most peaceful community species fall into this category. Sensitive species like neon tetras and shrimp do not.

Compatible with the broader hobby. Beginner-friendly species should let you grow into a normal community tank without constraining future choices. A betta locks you into a single-fish setup; a school of corydoras opens the door to dozens of compatible tankmates.

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

Species and patterns to avoid

The honest list of common beginner mistakes the hobby keeps making:

Goldfish in tanks under 200 litres

Goldfish are sold as starter fish and they shouldn't be. Common goldfish reach 30 cm and live 15+ years; fancy goldfish reach 20 cm. Both produce massive bioloads and need cold water (under 22°C). A goldfish in a 20-litre tank is a goldfish slowly dying. If you genuinely want goldfish, plan a 200-litre+ 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 750+ litre tanks. They're catfish, not algae cleaners. If you want a hardworking algae-eater for a normal community tank, look for bristlenose plecos instead — they stay at 12 cm and are genuinely beginner-friendly.

Bettas crammed into "betta cubes"

The 1–2 litre cube tanks sold for bettas are inhumane regardless of marketing. Bettas need at least 19 litres, with a heater and gentle filter. They're a wonderful first fish — in a properly-sized tank.

"Cycling" with hardy fish

Some pet shops still recommend 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 much larger than their juvenile shop sizes suggest. Bala sharks reach 35 cm; iridescent sharks reach 1 metre and are catfish, not sharks. None are appropriate for typical home aquariums.

Buying single specimens of schooling species

Many beginner fish — tetras, rasboras, corydoras — are schooling species that need groups of 6+ to behave naturally. Pet shops will happily sell you two neon tetras. Don't accept that. Either commit to a proper school or choose a non-schooling species.

Mixing aggressive cichlids with community fish

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

Know your tap water first

Your tap water determines what will thrive versus what will struggle. The single biggest beginner mistake after tank size is fighting your local water chemistry instead of working with it.

See our water parameters guide for full detail on each region, but 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 without remineralisation.
• Moderate water (Sydney): the most flexible — most community species work.
• Soft water (Melbourne): excellent for tetras and discus, challenging for livebearers and snails without supplementation.

Test your tap water before buying fish, not after. A 5-minute test prevents months of frustration.

Recommended starter fish by tank size and water type

The species below are all genuinely beginner-friendly, 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 requires advanced technique to keep alive.

Building a balanced community

A good community tank uses the vertical space — top, middle, and bottom of the tank are different habitats, and fish that occupy different levels make better use of the space 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 occupying 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 — at minimum 6, ideally 8–10. A school of 10 neon tetras shows behaviour and colour you'll never see in a group of 3.

Avoid mixing aggressive fin-nipping species (tiger barbs, serpae tetras) with long-finned species (bettas, fancy guppies, gouramis). The fin-nippers will systematically destroy the finnage.

Stocking timeline — when to add what

Even with a fully cycled tank, don't 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, triggering a mini-cycle and ammonia spike.

The realistic stocking pace:

• Week 1: add roughly a third of your intended stock — typically your first school or main centrepiece species.
• 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 — the bottom-dwellers or a second species.
• Week 5: add the final third.

This pace means your tank takes 5–6 weeks to become fully stocked from a finished cycle. That feels slow, but it's 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's hiding constantly, listing to one side, has clamped fins, white spots (ich), or visibly damaged fins.

Ask how long the fish has been at the shop. Fish freshly arrived from wholesalers are stressed and disease-susceptible. Fish that have been at a shop for two weeks or more without visible problems are a much safer purchase.

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

Always quarantine new fish in a separate tank for 2–3 weeks before adding to your main tank, particularly if you have established residents. This catches ich, internal parasites, and other diseases before they spread.

If you haven't set up your tank yet, start with how to set up a new aquarium. Once you've 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.