Best Pet Fish For Beginners (And Three To Avoid)

Two inches, peaceful, available in a dozen colors, and genuinely difficult to kill in a cycled tank. Platies tolerate a wide temperature and hardness range and will eat almost anything offered.

The catch: they are livebearers, so a mixed-sex group breeds continuously. Buy males only unless you want a population.

Males are small and brilliantly patterned, females larger and plain. Hardy, active, and endlessly interesting to watch.

They are also the animal behind some of the most important field experiments in evolutionary biology, after researchers moved guppies above Trinidad waterfalls and watched the population change within a few generations.

The catch: the same breeding problem as platies, and worse. Females store sperm, so one female can keep producing broods for months with no male present. Males only, or plan where the young will go. Buy from a local breeder if you can, since mass-produced fancy strains are often weak.

Small, striped, fast and almost indestructible. Zebra danios handle cooler water than most tropicals and forgive beginner errors better than anything else here.

The catch: they are shoaling fish and need a group of at least six, and they are energetic enough to stress calmer species. They also want swimming length rather than height.

Copper-orange with a black wedge, and a tight shoal of a dozen looks better than almost anything else in a planted tank. Peaceful, hardy and undemanding.

The catch: they need a group of eight or more to shoal properly, and in smaller numbers they hide and lose color.

Small armored bottom-dwellers that work the substrate constantly and have more personality than their size suggests. Peaceful with everything.

The catch: they are social and need six or more of the same species, and they need sand or smooth gravel, because sharp substrate damages their barbels. They are not a cleaning crew; they need their own sinking food.

A single betta is an excellent beginner fish, and it is also the species most commonly kept badly, because of how it is marketed.

It needs five gallons minimum, heated to around 78 to 80°F, filtered, with plants and places to hide. It does not live in puddles, does not eat plant roots, and does not want a vase.

The catch: one male per tank, and choose tankmates carefully, since long fins invite nipping.

Most barbs are too boisterous for a community tank. The cherry barb is the exception: small, calm, hardy, and the males turn deep red when settled.

The catch: they are shy in sparse tanks and need planting and a group of six or more to be confident.

Not for a beginner tank, despite being the fish most people start with, and the reasons are specific rather than snobbery.

Goldfish get large — fancy varieties 6 to 8 inches, common and comet goldfish 10 to 14 and really pond animals. They are messy enough to overwhelm a small filter, they are cold-water fish and so cannot share a tropical tank, and a single fancy goldfish needs something like 20 to 30 gallons on its own.

They also live 10 to 20 years, and the record holder reached 43. A goldfish is a decades-long commitment and a pond fish in waiting, which makes it a demanding first pet rather than an easy one.

Not as a first tank. Clownfish are hardy as marine fish go, but a saltwater setup needs salinity management, more equipment and more stable conditions than a freshwater one, and mistakes are more expensive in every sense.

If you do keep them later, buy captive-bred. They were among the first marine ornamental fish bred commercially at scale, captive-bred stock is hardier, and much of the marine trade still relies on wild collection, some of it using cyanide to stun fish on the reef.

These are sold in general pet shops without warning, and the adult size is usually the problem.

• Common pleco — sold at 3 inches, reaches 18 or more.
• Iridescent “shark” — a catfish that grows to 3 or 4 feet.
• Bala shark — 14 inches, and needs a shoal.
• Oscar — characterful and 12 to 14 inches, needing 55 gallons alone.
• Chinese algae eater — turns aggressive with age and stops eating algae.
• Feeder goldfish — kept badly and usually carrying disease.

And the rule behind all of them: look up the adult size of every fish before you buy it, because they do not grow to fit the tank. A fish in too small a space grows deformed internally and dies early.

For a cycled, planted, heated 20-gallon tank, one sensible combination:

• 8 harlequin rasboras in the middle water
• 6 corydoras catfish on the bottom
• 3 to 5 male platies or guppies for color

Add them in stages over several weeks rather than all at once, so the filter bacteria can keep up with the rising waste load, and test the water after each addition.

That is the whole secret, really. Choose small captive-bred fish, add them slowly, and give the bacteria time. The species you pick matters far less than the patience you show in the first two months.