10 best aquarium fish for beginners

The best first fish are hardy, peaceful species that suit your tap water and the size of your tank. Without a heater, White Cloud Mountain minnows (14–22 °C) and goldfish (10–21 °C) cope well indoors; in a heated tank with hard water, guppies and mollies are a good start. Shoaling species need a group of at least six, and a male betta should live alone. Only add fish once the tank has cycled.

The ten species below are beginner classics, but each has its own needs for space, temperature and company. The figures in this article come from Seriously Fish species profiles and RSPCA guidance; where the sources disagree, we say so. For setting up the tank itself, see our guide How to set up your first aquarium.

Quick comparison

Seriously Fish gives minimum tank size as a base footprint; the volume in brackets assumes a 30 cm tall tank (50 cm for the angelfish).

1. White Cloud Mountain minnow

The White Cloud Mountain minnow is one of the few aquarium fish that actually prefers cooler water. Seriously Fish gives a range of 14–22 °C and warns that permanently warmer water is likely to shorten its life, so in a well-insulated home it often needs no heater at all. It is a very peaceful shoaling fish: buy a group of 10 or more and give it a tank with a base of at least 60 × 30 cm. In a bigger group the fish are less nervous, and the males show their best colours as they compete for the females.

2. Guppy

The guppy is a colourful, very peaceful livebearer that suits a smaller tank (45 × 30 cm base). It is a hard-water fish: it may manage in soft or acidic water, but long term it needs moderately hard water or harder. The RSPCA gives guppies a tolerance of 22–28 °C, so they need a heater. Avoid fin-nippers such as tiger barbs. Breeding could hardly be easier – gestation takes 4–6 weeks and a female can drop anywhere from 5 to 100 young – so keep males only or plan for the fry.

3. Zebra danio

The zebra danio is hardy and very peaceful, and at 18–25 °C Seriously Fish notes that a heater may not always be needed. It is a busy swimmer, though: even a small group needs a tank with a base of at least 90 × 30 cm. Keep it in a group of at least 8–10 so it is less skittish and shows better colour. It mixes well with many popular species, from small barbs and rasboras to livebearers.

4. Molly

The molly is a peaceful livebearer with one important condition: it needs moderately hard to hard water (15–30 dGH) with an alkaline pH. In soft or acidic water, Seriously Fish says it weakens fairly quickly, showing as shimmying, fungus or clamped fins. Test your tap water hardness before you buy. Give it a base of at least 90 × 30 cm, 21–28 °C, and make a good share of its diet vegetable-based, such as blanched spinach or algae flakes.

5. Swordtail

The swordtail is a livebearer named after the extended lower lobe of the male's tail fin. It needs more room than many people expect: Seriously Fish puts the minimum at a 120 × 30 cm base. In cramped tanks the males form a pecking order and spend a lot of time defending their rank, so keep more females than males. It prefers moderately hard to hard water (10–25 dGH) at pH 7.0–8.0.

6. Siamese fighting fish

The betta is a popular first fish, but it is not a fish for a jar. Sources differ on tank size: RSPCA Australia recommends 20 litres or more (with 10 litres the absolute minimum), while Seriously Fish suggests a 45 × 30 cm base for a single male, around 40 litres. It needs a heater – the Anabantoid Association of Great Britain gives around 24–28 °C, RSPCA Australia 24–26 °C. Bettas are excellent jumpers, so fit a lid and leave an air gap beneath it, as they occasionally gulp air from the surface.

7. Neon tetra

The neon tetra is a peaceful shoaling fish for a tank with a base of at least 60 × 30 cm, at 21–25 °C in soft to moderately hard water. Buy a group of at least 8–10. Be choosy when buying: according to Seriously Fish, decades of commercial breeding have weakened ornamental neons, and deformities and poor health are widespread. Neons are also prone to neon tetra disease, which is virtually untreatable once advanced – avoid any tank where fish look restless, have white patches or keep apart from the shoal.

8. Angelfish

The angelfish is an elegant cichlid for anyone starting with a large, tall tank. Seriously Fish gives 100 × 40 × 50 cm, around 200 litres, as the smallest to consider, with at least 50 cm of height for adults. It is generally peaceful but can squabble with its own kind, so keep it in a small group. Crucially, it may eat small fish such as tetras, so angelfish and neons should not share a tank.

9. Goldfish

The goldfish is a cold-water fish that does well at 10–21 °C, so it rarely needs a heater. It does need plenty of space: the RSPCA recommends at least 60 litres of water for each goldfish, and bowls and jars are unsuitable. With good care, the RSPCA says goldfish can live for up to 25 years. They don't need company and can be kept alone; if you keep several, don't mix slim single-tailed fish with fancy twin-tailed varieties, which lose out at feeding time. More in our guide Goldfish care and tank size.

10. Koi

Koi belong in a garden pond, not an aquarium. Koi are an ornamental variety of the common carp, which according to the University of Florida can grow to more than a metre and live for at least 50 years. Like goldfish, they are a cool-water species with an optimum of roughly 18–24 °C, and they survive gradual seasonal swings from 0 to 35 °C. If you already have a pond, koi are a fine start; as a first "aquarium" fish they are not suitable.

How big a shoal should you buy?

Buy shoaling fish (White Clouds, neons, danios) together and as a group: the RSPCA says six or more, and Seriously Fish recommends 8–10 or more for these three species. In too small a group the fish are stressed and hide. With livebearers (guppies, mollies, swordtails), keep several females per male, as males pursue females relentlessly.

How to combine them?

For a community tank, choose 2–3 peaceful species with similar temperature and water-hardness needs. A few examples from the sources: Seriously Fish says White Clouds are not suitable companions for goldfish, even though they are often sold together; mollies should only share a tank with fish that tolerate hard water; and angelfish and neons don't mix. For stocking levels, the RSPCA suggests roughly 1.5–2 litres of water per 1 cm of tropical fish (excluding the tail) and 2 litres per 0.5 cm of goldfish – as a guideline only, since filtration, temperature and maintenance all affect water quality. Detailed needs for each species are in our aquarium fish directory, and feeding is covered in Feeding aquarium fish.

Frequently asked questions

What is the best aquarium fish for a beginner?

There is no single best fish – it depends on your tank and your water. Without a heater, White Cloud minnows and zebra danios do well indoors; in a heated tank with hard water, guppies are a reliable choice. Neon tetras and angelfish are more demanding: the first because shop stock is often of poor quality, the second because of the large tank it needs.

Can a betta live in a vase or bowl?

No. RSPCA Australia recommends a tank of 20 litres or more, and Seriously Fish explicitly does not support keeping bettas in tiny containers. A small bowl has no room for a heater, and a betta needs a steady 24–28 °C.

How many fish can I put in my tank?

As a guideline, the RSPCA suggests 1.5–2 litres of water per 1 cm of tropical fish, excluding the tail, and at least 60 litres per goldfish. Work from the adult size, not the size of the fish in the shop. An overstocked tank quickly pollutes the water and runs short of oxygen.

Does a beginner tank need a heater?

For tropical fish, yes: the RSPCA says you must include a thermostatically controlled heater set to the right temperature for the species. Goldfish (10–21 °C) and White Cloud minnows (14–22 °C) usually don't need one, and permanently warm water can actually harm White Clouds.

How long should I wait before adding fish to a new tank?

The RSPCA says fishless cycling takes at least two weeks, though there is no exact rule. Test the water every other day and add fish only after ammonia and nitrite have risen and then fallen back to 0. The process is explained in Cycling an aquarium: the nitrogen cycle.

Can goldfish live with tropical fish?

It isn't recommended. Goldfish need cooler water (10–21 °C) than most tropical species, and a lot of space. Even the White Cloud minnow, often sold as a goldfish companion, is not a suitable tankmate according to Seriously Fish.