7 Best Fish for 20-Gallon Tank (A Beginner’s Guide)

If you’re looking to add some excitement and life to your 20-gallon home aquarium, choosing the right fish is essential.

There are a few things to keep in mind. The type of fish you choose should be compatible with both the size of the tank and the other fish that will be sharing its space. In addition, you need to consider the level of care required for each type of fish.

In this post, I’ll show you how to choose the right fish for your tank, based on their size, species, and personality. I’ll also share a list of my favorite picks for each category so you can make an informed decision on what to buy.

Fish Stocking Tips for a 20-Gallon Tank

When stocking a 20-gallon tank, it’s important to remember that even though the tank may be small, it’s still a tiny ecosystem. This means that care and maintenance are crucial to keeping your fish healthy and happy. Here are a few tips to help you get started:

  • It is important to consider the type of fish you want, as well as the stocking density, or how many fish can comfortably live in the space. A good rule of thumb is one inch of fish per gallon of water. So, for a 20-gallon tank, you could have up to 20 inches of fish.
  • Don’t overdo it. It can be tempting to want to fill up your tank with as many fish as possible, but resist the urge! Overcrowding will only lead to problems down the road.
  • Another important factor is the compatibility of the fish you’re planning to stock. Some fish are peaceful and can live together harmoniously, while others are more aggressive and need to be kept separate. Make sure to do your research before adding any new fish to your tank.
  • If you are interested in a community fish tank, common choices include guppies, mollies, and platies. These species are relatively peaceful and can tolerate a wide range of water conditions.
  • Finally, don’t forget to provide hiding places and plenty of oxygenation for your fish. Aquarium plants are a great way to do this, as they help with both filtration and oxygenation.

7 Best Fish for a 20-Gallon Tank

With the fish temperament, level of care, and compatibility in mind, here are a few of the best fish for a 20-gallon tank.

1. Platy

  • Size: 2 to 3 inches
  • Care: Easy
  • Number of Fish in a 20-Gallon Tank: 6 to 8

Platies are an attractive and active freshwater fish that are relatively peaceful, making them a good choice for beginners and experienced aquarium keepers alike. These hardy fish can tolerate a wide range of water conditions.

A 20-gallon tank is a great size for keeping platy fish. These undemanding omnivores are a colorful addition to any aquarium. They do well on a diet of flakes, frozen, and dried food. The ideal temperature for platy fish is 70-82 degrees Fahrenheit. With proper care, platy fish can live for 3-5 years.

2. Swordtails

  • Size: 5 to 6 inches
  • Care: Easy
  • Number of Fish in a 20-Gallon Tank: 3

Swordtails are a beautiful tropical freshwater fish that come in a variety of colors. They are a live-bearing fish that are easy to care for.  They get their name from their sword-like appearance. Swordtails are omnivores, so they need a diet that consists of both plant and animal material. They also prefer plenty of light and a pH level that is between 6 and 7.

Swordtails like to hide in live plants and are active swimmers. The ideal water temperature for swordtails is 72-79 degrees Fahrenheit. They can live for 3 to 5 years if they are properly cared for.

3. Panda Corydoras

  • Size: 2 inches
  • Care: Easy
  • Number of Fish in a 20-Gallon Tank: 6 to 8

Panda corydoras are one of the smallest Cory Catfish species and do well in groups of six or more. They are peaceful scavengers that spend most of their time near the bottom of the tank.

Panda Cory are black and white with large eyes. They prefer a water temperature of 72-77 degrees Fahrenheit and will do best on a diet of sinking pellets or frozen foods.

Corys reproduce by laying sticky eggs on plants or other surfaces in the aquarium. The fry (young fish) can be difficult to raise, but adult fish are relatively easy to care for.

4. Goldfish

  • Size: 4 to 6 inches
  • Care: Easy
  • Number of Fish in a 20-Gallon Tank: 2 to 3

Goldfish are part of the Cyprinidae family and are known for being hardy and easy to care for. They come in a variety of colors, but the most common are gold and orange. These fish are peaceful by nature and do well with other fish that are similar in size.

Goldfish are omnivorous scavengers, which means they will eat both plants and animals. However, it’s important to give them a varied diet that includes both fresh and frozen food. Goldfish prefer water that is 68 to 74 degrees Fahrenheit and they can live 10-15 years with proper care.

5. Fancy Guppies

  • Size: 1.5 to 2 inches
  • Care: Easy
  • Number of Fish in a 20-Gallon Tank: 8 to 10

If you’re looking to add a splash of color to your 20-gallon freshwater tank, guppies are a great option. These small, brightly colored fish are relatively easy to care for and make a fun addition to any aquarium.

Guppies are omnivorous, so they will eat just about anything you give them. A good quality flake food will provide them with all the nutrients they need. 

Fancy Guppies also require specific water conditions. The water temperature should be between 72-82 degrees Fahrenheit. The pH of the water should be between 6.8 and 7.6. It is also important to maintain moderate water hardness levels. They can live for about two to three years.

6. German Blue Ram

  • Size: 2 to 2.5 inches
  • Care: Easy
  • Number of Fish in a 20-Gallon Tank: 2 to 3

A German Blue Ram is a beautiful South American dwarf cichlid that is perfect for a 20-gallon tank. They are peaceful fish that can be kept with one male and one or two females. They are known for their bright blue colors and their diet consists of plant matter and small insects.

German Blue Ram are easy to care for and have a lifespan of 2-3 years. The ideal temperature for them is 84-86 degrees Fahrenheit.

7. Apistogramma

  • Size: 3 inches
  • Care: Easy
  • Number of Fish in a 20-Gallon Tank: 3 to 4

The Apistogramma is a freshwater fish that is part of the Cichlidae family. They are found in South America and adult fish typically range in size from two to three inches.

Apistogramma are carnivores and their diet consists of live foods such as baby brine shrimp, larvae of other fish, and glass worms. The recommended water temperature for these fish is 73-82 degrees Fahrenheit. They can live up to five to ten years with proper care.