Plan a healthy fish tank before you buy a single fish.

Stocking calculator

How many fish fit, and can they live together? Bioload, water, groups and compatibility in one check.

Compatibility checker

Compare two or more species and see exactly why they work or clash.

Tank mates finder

Good, risky and bad tank mates for every species, with a reason for each.

My tanks

Save your tanks, log water tests and get water change reminders. Stays in your browser.

Aquarium calculators

Volume, gravel, heater size, filter flow, water changes and unit conversions.

Equipment checklist

Everything a new tank needs, with heater, filter and gravel sizes for every common tank.

Compatibility chart

The 30 most popular fish on one printable chart.

Angelfish

15 cm (5.9 in) · 29+ gallons

The angelfish is a tall, graceful South American cichlid that grows about 15 cm (6 in) long and even taller with its fins. It makes a classic community centerpiece, but it needs a tall tank and will eat small fish such as neon tetras.

Betta fish

6.5 cm (2.6 in) · 5+ gallons

The betta is a colorful, long-finned labyrinth fish that breathes air at the surface and is usually kept alone. Give it a heated, filtered tank of at least 5 gallons (19 L), ideally 10 (38 L), with gentle flow and never another male betta.

Bristlenose pleco

12 cm (4.7 in) · 20+ gallons

The bristlenose pleco is a small, hardy catfish that stays around 4–5 inches (12 cm) and grazes algae day and night. It's one of the best algae eaters for tanks of 20 gallons (76 L) or more, but it needs driftwood, a cave and vegetables, not just leftover algae.

Bronze corydoras

7 cm (2.8 in) · 20+ gallons

The bronze corydoras is a hardy, peaceful South American catfish that spends its day sifting the bottom for food. It is one of the easiest corys for beginners, but it needs a group of 6 or more, soft sand and its own sinking food.

Cherry shrimp

3 cm (1.2 in) · 5+ gallons

Cherry shrimp are small, hardy freshwater shrimp bred in red, blue, yellow, orange, green and black. They graze algae and leftovers and breed readily in a planted tank, but they need stable water, no copper and no fish big enough to eat them.

Common goldfish

30 cm (11.8 in) · 75+ gallons

The common goldfish, including the comet and shubunkin, is a hardy, fast cool-water fish that often reaches 12 in (30 cm) or more. It needs a very large tank, at least 75 gallons (284 L) for one, or a pond, plus strong filtration and no tropical tankmates.

Common pleco

40 cm (15.7 in) · 150+ gallons

The common pleco is the armored sucker catfish sold as a small algae eater, but it grows to 12–18 inches (30–45 cm) or more. An adult needs a tank of at least 150 gallons (570 L) and 6 ft (180 cm) long, so it suits very few home aquariums.

Dwarf gourami

7.5 cm (3 in) · 15+ gallons

The dwarf gourami is a 3 in (7.5 cm) labyrinth fish whose males shine electric blue and red. It suits a calm, planted community tank of 15 gallons (57 L) or more. Keep only one male, and buy with care: many farmed fish carry disease.

Fancy goldfish

15 cm (5.9 in) · 20+ gallons

Fancy goldfish are slow, round-bodied goldfish such as orandas, ryukins and black moors. They are messy cool-water fish that need about 20 gallons (76 L) for the first fish plus 10 gallons (38 L) for each extra, strong filtration and no tropical tankmates.

Guppy

5 cm (2 in) · 10+ gallons

The guppy is a small, colorful livebearer and one of the easiest fish to start with. Males have big flowing tails, while females are larger and plainer. Keep guppies in hard, alkaline water and plan for babies, because they breed nonstop.

Neon tetra

3.5 cm (1.4 in) · 15+ gallons

The neon tetra is a tiny, peaceful schooling fish with a glowing blue stripe and a red rear half. It is one of the easiest and most popular community fish, but it needs a group of 8 or more and a mature, stable tank.

Nerite snail

2.5 cm (1 in) · 5+ gallons

Nerite snails are small, patterned snails that scrape algae off glass, rocks and leaves without harming plants. Their eggs can't hatch in fresh water, so they never overrun a tank, but they need hard water, enough algae to eat and a tight lid.

Red Spots on Fish: What Causes Them and What to Do Today

Red spots on a fish's body, fins or scales can mean ammonia burns, infection, parasites, injury or normal color. Tell them apart and act the same day.

White Fuzz on Fish: Fungus or Columnaris? How to Tell and Treat

White fuzz on a fish's fin, body or mouth is usually fungus or columnaris. Learn how to tell them apart, rule out ich and mucus, and what to do first.

How to Tell If a Fish Is Pregnant: 5 Signs and When Fry Arrive

How to tell if a fish is pregnant: check the gravid spot, belly shape and behavior, then see how long guppies, mollies and platies take to give birth.

Why Is My Betta Fish Losing Color? 6 Causes and When to Worry

Betta fish losing color or turning white? Learn the six common causes, how to tell stress, marble genes, columnaris and velvet apart, and what to do today.

Fish Tank Smells Bad? Rotten Egg, Fishy and Musty Smells Fixed

Rotten egg, fishy or musty fish tank smell? Match the smell to its cause, find the source in minutes, and fix it safely without tearing the tank down.

How to Tell If a Fish Is Male or Female: 8 Fish, Easy to Tricky

How to tell if a fish is male or female: check color, fins, body shape and the gonopodium, with species-by-species tips for guppies, bettas, angelfish and more.