7 Popular Fish you should Try in A 20-Gallon Aquarium

7 Popular Fish You Should Try in a 20-Gallon Aquarium

20-gallon aquariums are one of the most popular tank sizes among fish keepers because they’re small enough to keep in a bedroom but big enough that you can choose from a wide variety of fish to keep. Check out these freshwater fish for a variety of interesting behavior and beautiful colors to spice up your aquarium.


7. Julidochromis

This stunning, three-inch fish is the perfect choice if you’ve ever wanted to try keeping Tanganyikan cichlids. They have the amazing ability to swim vertically, sideways, and upside-down in order to stay close to surfaces and hiding spots. To make them feel at home, provide lots of rockwork and other natural habitats. Depending on the amount of cover provided, you can keep three to six of them in a 20-gallon long tank or maybe a single breeding pair in a 20-gallon high tank. The Julies are a peaceful, calm fish. They can be paired with other African fish or fish in the same tank.

Julidochromis ornatus (or the golden Julie) is one of the most popular varieties because of its colorful markings and small size.

6. Leopard Danio

You are looking for an interactive fish that is hyper and doesn’t mind saying hello? Check out the leopard danio! The brightly-spotted schooling fish is similar to a small trout. It comes in both long and short fins. This is the best thing about danios – they can live at any temperature without heating and can tolerate a wide range in pH and water hardness. Get a group of six, and watch them speed around the top third of the fish tank. Pair them with other mid-water fish such as rasboras or tetras to keep them from eating all the food. This will make for an entertaining aquarium.

Leopard Danios are a budget-friendly, easy-to-use schooling fish that isn’t nearly as well-known as their cousin, the Zebra Danio.

5. German Blue Ram

Speaking of boldly patterned fish, take a look at the German blue ram, or Mikrogeophagus ramirezi. A 20-gallon aquarium can hold one male and one or two women. A female has a shorter dorsal ray, pinkish belly and blue spangles within the black spot. The male is bigger, has a longer dorsal fin, pinkish belly, and blue spangles within her black spot. It is important to keep in mind that this South American dwarf catfish prefers higher temperatures, around 85°F.

German blue Rams are monogamous, and have a tendency to show parental love for their young. This picture shows the male and female.

4. Harlequin Rasbora

Trigonostigma heteromorpha, another schooling fish, is a popular choice. It can be kept in groups of six to eight. Their distinctive black triangular patch and bright orange coloration really stand out in a lushly planted tank. Growing to only two inches long, this hardy, beginner-friendly fish will do well in a community tank with other docile inhabitants. You can find more information in our care guide on caring for rasboras.

Harlequin rasboras are social creatures that tend to swim in the middle to top sections of an aquarium.

3. Apistogramma

Apistogramma cacatuoides and Apistogramma agassizii are two of the most popular members of this large genus of South American dwarf cichlids. Apistos are similar to the German blue ram. They are brightly colored and love to be in the bottom third. They also prefer warmer temperatures, around 82 degrees F. If you provide breeding caves, the female will pair up with her chosen male, protect her eggs, and care for the young. Baby brine shrimp can be used as fry food. Learn more about them in our Apistogramma care guide.

This male Apistogramma catuoides has brightly colored, long dorsal fins. His female counterpart is smaller and yellows during spawning.

2. Panda Corydoras

Unlike larger species of cory catfish, Corydoras panda only grows to 1.75 to 2 inches long, so you can easily get a group of six or more for a 20-gallon aquarium. This peaceful bottom dweller can be kept in cooler temperatures from 72 to 77degF. They will use the barbels and whiskers in their mouths to find their favorite food, Repashy gel foods, and frozen bloodworms. Keep them happy and well-fed, and soon you may see some breeding behavior and sticky eggs covering the tank walls. For more details, read our cory catfish care guide.

Panda cory catfish are a crowd favorite because of their unique black and white coloration.

1. Pseudomugil gertrudae

This smaller rainbowfish is well-known for its bright yellow body and brilliant blue eyes. A group of six or more male rainbowfish will perform a showy dance with their fins if they are both genders. The spotted blue-eye rainbowfish is our favorite because of its unique appearance and interesting behavior. You may find them more expensive and harder to find depending on where they live. But if you place them in a tank with a black background, you’ll be amazed at their beauty.

You could use spawning mops made from yarn to encourage rainbowfish eggs to hatch. After that, you can remove the mop to raise fry in a separate tank.

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