Best freshwater fish for Australian tap water

The fish that thrive in your tank are mostly decided before you buy them, by the water already in your pipes. Here is how to match freshwater fish to your local Australian tap water, region by region.

Published 17 June 2026 · Last updated 18 June 2026 · 13 min read

Start with your water, not the fish

The most useful decision in Australian fishkeeping is made before you buy a single fish: it is choosing species that suit the water already coming out of your tap. Your tap water has a fixed hardness (its mineral content, measured as GH) and a fairly stable pH. Both are difficult and risky to change long-term. Fish matched to your water settle in and thrive; fish fighting your water spend their lives mildly stressed, colour up poorly, and fall ill more easily.

Of the two, hardness matters more than pH for most fish. GH measures the dissolved minerals (mainly calcium and magnesium) that fish have evolved to balance against. Soft-water fish struggle to regulate their internal salts in mineral-rich water, and hard-water fish struggle in mineral-poor water. For the full background on each parameter, see our water parameters guide.

Find out what comes out of your tap

You cannot match fish to your water until you know what your water is. There are two easy ways to find out:

Test it yourself. A GH and KH test kit gives you a direct reading. The API Freshwater Master Test Kit covers pH, ammonia, nitrite, and nitrate; the GH and KH kit is sold separately and is worth having. Fill a clean glass from the tap, let it sit for a few hours to off-gas, then test.

Check your water authority's report. Most Australian utilities publish water quality data by area (SEQ Water, for example, publishes monthly reports). Look for hardness, usually given as mg/L of calcium carbonate, which is the same as ppm.

Hardness is reported as either ppm (parts per million) or dGH (degrees of general hardness). The conversion is 1 dGH = 17.86 ppm, and our hardness converter handles it both ways. As a rough guide: under about 70 ppm (4 dGH) is very soft, 71 to 140 ppm (4 to 8 dGH) is soft, 141 to 210 ppm (8 to 12 dGH) is moderate, 211 to 320 ppm (12 to 18 dGH) is hard, and above 320 ppm (18 dGH) is very hard.

Australian tap water by region

Australian tap water varies widely, but the broad regional picture is consistent enough to plan around:

• South East Queensland (Brisbane, Gold Coast, Sunshine Coast): soft to moderate but alkaline. Suits livebearers, snails, and most community fish.
• Adelaide: moderate to hard and alkaline, harder than South East Queensland.
• Perth: very hard in most areas. Best suited to hard-water fish.
• Sydney: very soft to soft and slightly alkaline. The most flexible Australian water, supporting a broad range of species.
• Melbourne: very soft and slightly acidic to neutral. Excellent for soft-water fish, harder for livebearers and snails.

For the detailed regional profiles, including typical GH and pH figures, see the Australian section of our water parameters guide.

The lists that follow are a representative starting point, not a complete catalogue. Many more suitable fish exist for each water type, and your local shop's stock will shape the final choice. Species shown as links have a full care guide; the rest are equally good options to research.

Best fish for hard or alkaline water

If you are in Brisbane, the Gold Coast, Adelaide, or Perth, your water is alkaline and mineral-rich (hard in Adelaide and Perth, softer but still alkaline in Brisbane and the Gold Coast), and a wonderful range of fish genuinely prefer it. This is an advantage, not a limitation.

Livebearers are the stars. Guppies, platies, Endler's livebearers, mollies, and swordtails evolved in hard, mineral-rich water and show their best colour and health in it. They are hardy, active, and breed readily.

• Guppy, endlessly varied in colour and comfortable to 30 dGH
• Platy, a slightly larger, peaceful livebearer
• Endler's livebearer, a smaller, vividly patterned relative of the guppy
• Molly, a larger livebearer that appreciates even harder water and needs more room
• Swordtail, an active livebearer named for the male's extended tail fin

Rainbowfish are an underrated choice for hard Australian water. Australian and New Guinea rainbowfish are built for hard, alkaline conditions, are widely stocked here, and develop superb colour in a mature tank. Look for Boeseman's rainbowfish or the smaller dwarf neon rainbowfish for a community tank. For native options that thrive in the very same water, see our guide to native Australian fish.

Snails and shrimp thrive too. Hard water provides the minerals snails need to build their shells, so a hard-water tank is the easiest place to keep them.

• Mystery snail and nerite snail, both excellent algae grazers
• Rabbit snail, a slow, characterful larger snail
• Assassin snail, which helps control pest-snail outbreaks
• Cherry shrimp and amano shrimp, which colour up and breed well in harder water

For a hard-water centrepiece, the electric yellow cichlid is a striking African rift lake fish that needs genuinely hard, alkaline water, best supplied by Adelaide and Perth (softer Brisbane and Gold Coast water may need a little added mineral hardness). It and other rift lake cichlids are semi-aggressive and need a larger species-appropriate tank, so they suit a keeper ready to plan around them rather than a first community tank.

In hard or alkaline water, avoid soft-water specialists like neon tetras, chili rasboras, and the German blue ram unless you are prepared to soften your water, which is ongoing work (see adjusting your water below).

Best fish for soft, acidic water

Melbourne's soft water is ideal for some of the most popular fish in the hobby, the ones that often struggle in the rest of the country. If your water is soft, this is your strength.

Tetras and rasboras shine. These South American and South East Asian fish come from soft, often tannin-stained water, and their colours are most intense in it.

• Neon tetra and ember tetra, classic soft-water schooling fish
• Cardinal tetra, like a neon but larger and even more vivid, and rummynose tetra, a tight-schooling fish whose red nose fades when water quality slips
• Lemon tetra and glowlight tetra, gentle, hardy soft-water schoolers
• Chili rasbora, a tiny, glowing nano fish
• Harlequin rasbora, hardy and forgiving across soft to moderate water

Small soft-water specialists add interest at the surface and mid-water: the sparkling gourami, a thumb-sized labyrinth fish that audibly croaks, and the marbled hatchetfish, a true surface-dweller that needs a tight-fitting lid.

Dwarf cichlids are an option here. The German blue ram is a soft-water gem, though it needs warmth and stable conditions. The Bolivian ram is the more forgiving, beginner-friendly alternative. For a soft-water centrepiece with personality, apistogramma (the cockatoo and Agassiz's dwarf cichlids) are superb.

Bottom-dwellers do well too: kuhli loaches, otocinclus, and bronze or pygmy corydoras all suit soft to moderate water, as does the slightly more delicate panda corydoras.

Soft to moderate water and reliable all-rounders

Sydney's soft to moderate, slightly alkaline water is the most flexible in the country. Most peaceful community fish work without any adjustment, including the great majority of tetras, rasboras, barbs, corydoras, and gouramis, which makes it an easy place to keep a varied tank.

Wherever you are, some fish are genuinely happy across the full Australian range, from soft Melbourne water to hard Perth water. These all-rounders are the safest possible starting point:

• Zebra danio, one of the toughest, most adaptable fish in the hobby
• White cloud mountain minnow, hardy and happy even in cooler rooms
• Bronze corydoras and the peppered corydoras, forgiving across a wide range
• Cherry barb, plus the equally adaptable gold barb and odessa barb
• Pristella tetra and black skirt tetra, two of the most hardness-tolerant tetras
• Harlequin rasbora and honey gourami, peaceful and tolerant
• Bristlenose pleco, a hard-working algae eater that suits almost any water
• Paradise fish and kribensis, hardy options for a keeper wanting something with more character

Quick reference by water type

Match your tested water to the row below. "Best-suited stars" are the fish that genuinely prefer that water; the all-rounders are happy almost anywhere. Linked species have a full care guide; the rest are equally good options to research.

Once you have a shortlist, our stocking calculator checks that your chosen fish actually fit together and suit your tank size, water, and group needs.

Adjusting your water: when it's worth it

You can change your water's hardness, but for most beginners the honest advice is: don't. Adjusting water is ongoing work, adds cost, and a lapse causes the parameter swings that stress fish far more than stable, slightly-off water ever would. Matching fish to your tap water is almost always the better choice.

That said, there are two legitimate reasons to adjust: a breeding project that needs specific conditions, or a single must-have species your water doesn't suit. If you go ahead:

• To soften hard water: mix in reverse-osmosis (RO) water or collected rainwater, and add botanicals like Indian almond leaves or peat for a gentle, natural softening. RO water should be remineralised back to a controlled level rather than used pure.
• To harden soft water: add crushed coral to the filter or substrate, or dose a GH remineraliser such as Seachem Equilibrium. Both raise mineral content steadily.

For nearly everyone, the path of least resistance is also the path to the healthiest fish: test your water once, identify which group it suits, and choose from the fish that already want to live in it.

To understand the numbers behind your water, see our water parameters guide and hardness converter. New to the hobby? Start with how to choose your first fish and how to set up a new aquarium. To plan a compatible tank, use the stocking calculator or browse the full species directory.