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. With all these possibilities, check out our favorite freshwater fish to spice up your aquarium with their beautiful colors and interesting behaviors.
This magnificent, three-inch fish makes a great choice for anyone who wants to keep Tanganyikan cichlids. They have the amazing ability to swim vertically, sideways, and upside-down in order to stay close to surfaces and hiding spots. They will feel at home if you provide them with plenty of rockwork that simulates their natural habitat. Depending upon the amount of cover, you can keep between three and six of them within a 20-gallon tall tank. One breeding pair may be kept in a 20 gallon high tank. Compared to other African cichlids, Julies are relatively peaceful fish and can cohabitate with other small community fish that prefer swimming in the middle or top of the tank.
Julidochromis ofnatus, or the golden Julie is one the most sought-after varieties. Its small size and colorful markings make it a very popular variety.
6. Leopard Danio
You are looking for a hyper-interactive fish that doesn’t mind saying hello? Look at the leopard danio! This brightly colored schooling fish has the appearance of a small trout. This is the best thing about danios – they can live at any temperature without heating and are comfortable in all pH and water hardness levels. Take six of them and watch their speeding around the top of the tank. For a very entertaining aquarium, pair them up with other fast-moving midwater fish such rasboras and tetras.
Leopard danios are an easy, budget-friendly schooling fish that aren’t as commonly seen as their famous 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. A 20-gallon aquarium can hold one male and one or two women. A female will have a smaller dorsal fin and a pinkish belly. There are blue spangles in the black spot to her side. The male, however, is larger with a longer dorsal beam and no blue spangles. It is important to keep in mind that the South American dwarf catfish likes higher temperatures, around 85°F.
German blue rams are monogamous and show parental care for their young. This image shows the male on the left and female on the right.
4. Harlequin Rasbora
Trigonostigma heteromorpha (a schooling fish) is another popular one. They do well in a small group of six to eight. The fish’s distinctive triangular black pattern and bright orange coloration stand out in a beautifully planted tank. This hardy fish, which can grow up to 2 inches, is perfect for beginners and will be happy in a tank with other docile fish. Read our complete care guide for more information.
Harlequin Rasboras, social creatures, tend to swim in middle-to-top sections of aquariums.
Apistogramma cacatuoides and Apistogramma agassizii are two of the most popular members of this large genus of South American dwarf cichlids. Much like the German blue ram, Apistos are very colorful, like to hang out in the bottom third of a tank, and prefer warmer temperatures around 82degF. If you offer breeding caves, the female can pair up with her male choice, protect her eggs, care for her young, and will even be able to breed. As a fry food, you can offer baby brine shrimp to her. 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 calm, bottom-dweller can be kept at temperatures as low as 72°F to 77°F. They love to use the barbels and whiskers in their mouths to find their favorite food, Repashy gel foods, and frozen bloodworms. 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 panda cory catfish are popular for their unique black-white coloration.
1. Pseudomugil gertrudae
This smaller rainbowfish is known to have piercingly blue eyes, bright yellow bodies, and spotted Finnage. A group of six or more males can compete for attention with their stunning fins by performing a showy dance. 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, they’ll blow your mind.
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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