How to choose the right fish tank

Updated June 2026Independently researchedNo paid placement.

What size aquarium should a beginner choose?

A 10- to 20-gallon tank is the sweet spot for newcomers. Smaller tanks, like a 5-gallon, can work but require stricter water management because any mistake is amplified in a tiny volume. A larger tank offers more stability and gives you room to keep a small community of fish without constant worry. That said, don’t go bigger than 40 gallons for your first tank. Extra water volume means extra weight (a 20-gallon can weigh over 200 pounds when full) and more effort for water changes. The goal is to pick something big enough to be forgiving but small enough to maintain with a weekly routine. Consider the tank’s footprint, not just its gallon count. A 20-gallon long (30 inches wide) gives fish more horizontal swimming space than a tall 20-gallon. Most starter kits come in standard rectangular shapes, which are easiest to light and clean.

Glass or acrylic: which is better for a starter tank?

Glass tanks are the default choice for beginners and for good reason. They resist scratching, don’t yellow over time, and cost less. The main downside is weight, a glass 20-gallon tank is considerably heavier than an acrylic one, and they can break if dropped or struck. Acrylic tanks are lighter and more impact-resistant, but they scratch very easily. Even wiping algae with a standard scrubber can leave permanent marks. Acrylic also tends to be more expensive. For a first tank, glass is the pragmatic pick: it’s budget-friendly, durable enough for normal handling, and easier to keep looking clean. If you do choose acrylic, plan to use only a soft algae pad and avoid gravel that might get sucked into the filter intake and scratch the interior. In either case, make sure the tank sits on a level, dedicated stand or sturdy surface.

What equipment matters most in a starter kit?

A good starter kit typically includes a tank, lid, light, and filter. The two components where you should not compromise are the filter and the heater. Look for a hang-on-back (HOB) filter that turns over at least 4 to 6 times the tank volume per hour. Many kits come with undersized filters, so read reviews to see if owners swap them out. Heaters are often the weakest link in budget kits. A preset heater might hold temperature within a range, but an adjustable heater gives you finer control. For a 10- to 20-gallon tank, a 50- to 100-watt adjustable heater is standard. Always pair it with a simple aquarium thermometer to double-check. The LED light in many starter kits is fine for viewing and low-light plants like java fern or anubias. If you want a planted tank, you’ll likely need a stronger, full-spectrum light sold separately. Also, the included lid is usually a plastic frame with a thin plastic sheet, it works, but won’t last forever.

What is fishless cycling and how do I do it?

Fishless cycling is the process of establishing beneficial bacteria in your filter and substrate before adding fish. These bacteria convert toxic ammonia (from fish waste) into nitrite, then into less harmful nitrate. Skipping this step is the most common cause of sick or dying fish in new tanks. To cycle, fill the tank, add a source of ammonia (pure ammonia or a pinch of fish food), and test the water every few days with a liquid test kit. You’ll see ammonia spike, then nitrite appear, then nitrate. When the tank can turn 2 ppm of ammonia into nitrate within 24 hours, typically after 4 to 8 weeks, it’s cycled and safe for fish. Be patient. Adding a “bottled bacteria” product can speed things up but isn’t a magic shortcut. Never rely on “instant cycle” claims. Fishless cycling is the most humane and reliable method, and it’s worth the wait.

Which fish are easiest for a new tank?

Hardy, small community fish are your best bet. Guppies, platies, zebra danios, and cherry barbs all adapt well to a cycled 10- to 20-gallon setup. They tolerate minor water parameter swings better than delicate species. Corydoras catfish are also a great bottom-dweller choice, but they prefer to be in groups of at least three. Avoid goldfish for a small starter tank, they grow large, produce a huge waste load, and need much more space. Bettas can work in a 5- to 10-gallon tank (with a gentle filter and heater), but they should live alone or with very peaceful tankmates. Always research each species’ adult size and temperament before buying. Don’t overstock. A good rule of thumb is one inch of adult fish per gallon for small, low-waste fish, but use a reliable online stocking calculator for your exact tank dimensions and filtration. It’s far better to understock than to deal with aggression and poor water quality.

How much daily and weekly maintenance does a small aquarium need?

Daily tasks: check that the temperature is stable, look for any sick or stressed fish, and feed once a day (only as much as they eat in about a minute). A quick glance at the filter to make sure it’s flowing normally is smart. Weekly chores take about 20 to 30 minutes. Replace 25% of the water with dechlorinated tap water, use a gravel vacuum to pull out debris, and rinse the filter sponge in a bucket of old tank water (never tap water, which kills bacteria). Wipe algae off the glass with a dedicated algae pad. Test for ammonia and nitrite every couple of weeks once the tank is mature. Every month or so, replace mechanical filter media as it wears out, and check that the heater and light are still working properly. With a consistent routine, a small aquarium stays clear and healthy. Neglect it for a week or two, and you’ll likely see algae blooms or a fish health decline.

Frequently asked questions