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. You have many options. Here are our top picks for freshwater fish to add color and interest to your aquarium.


7. Julidochromis

If you have ever dreamed of keeping Tanganyikan Cichlids, this stunning fish of three inches is the right choice. These fish can swim upside-down, sideways, vertically and horizontally to avoid hiding places and surfaces. To make them feel at home, provide lots of rockwork and other natural habitats. You can house three to six depending on how much cover you provide. Or, keep one breeding pair in a 20 gallon tank. Julies are peaceful fish, and they can live with other African cichlids.

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


6. Leopard Danio

Looking for a hyper, interactive fish that isn’t afraid to say hello? The leopard danio is a hyper, interactive fish that will say hello! This brightly spotted schooling fish has a similar appearance to a little trout. They come in both short- and long-fin varieties. These danios are extremely resilient and can survive at room temperature without the use of a heater. They also thrive in all water pH levels and hardnesses. You can watch them race around the tank’s top third in a group of six. For a very entertaining aquarium, pair them up with other fast-moving midwater fish like rasboras and tetras.

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

If you are looking for boldly patterned fish, the German blue ram or Mikrogeophagus ramirezi is it. One male can be housed in a 20-gallon aquarium with one or two females. A female has a shorter dorsal fin, pinkish belly, and blue spangles inside the black spot on the side of her body. A male, on the other hand, is larger, has an extended dorsal ray, and no blue spangles inside his black spot. The key thing to remember is that this South American dwarf cichlid likes higher temperatures around 85degF, so keep them with other hot water fish like cardinal tetras and Sterbai cory catfish.

German blue Rams are monogamous, and have a tendency to show parental love for their young. In this picture, the male is on the left, and the female is on the right.

4. Harlequin Rasbora

Trigonostigma heteromorpha is another popular schooling fish that does great in a group 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. For more information on caring for rasboras, read our full care guide.

Harlequin Rasboras, social creatures, tend to swim in middle-to-top sections of aquariums.

3. Apistogramma

Apistogramma cacatuoides is the most well-known member of this large genus. Apistogramma gagassizii is another popular member of this large group of South American dwarf Cichlids. Apistos, much like the German blueram, are colorful and like to hang out at the bottom of a tank. They prefer temperatures between 82 and 83 degrees F. If you provide breeding caves, the female will pair up with her chosen male, protect her eggs, and care for the young. Help her out by offering baby brine shrimp as fry food and keeping the water quality as clean as possible. Learn more about them in our Apistogramma care guide.

The male Apistogramma Cacatuoides has long and brightly-colored dorsal Fins. While his female counterpart is smaller, it turns yellow during spawning.

2. Panda Corydoras

Corydoras can be kept in 20 gallon tanks. They are smaller than the larger cory catfish species. The temperature range for this peaceful bottom dweller is 72-77 degrees F. To scavenge their favorite foods such as Repashy gel food and frozen bloodworms, they use the whiskers or barbels around their mouths. You will soon notice breeding behavior and sticky egg coverings in your tank walls if you keep them happy. 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

The smaller rainbowfish is known to have piercing blue eyes and bright yellow bodies. It also has spotted finnage. A group of six or more male rainbowfish will perform a showy dance with their fins if they are both genders. We chose the spotted blue-eye rainbowfish as our number one pick because of their colorful appearance, interesting behavior, and uniqueness in the hobby. 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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