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.
If you ever wanted to keep Tanganyikan cichlids, then this fish of incredible size is for you. 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. Depending on the amount you provide cover, you can keep up to six in a 20-gallon-long tank. You could also have one breeding pair in an 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 Ornatus, also known as the golden Julie, is one of the most loved varieties due to its small size and colorful markings.
6. Leopard Danio
Are you looking for an interactive, hyper fish that will say hello and is willing to share his thoughts? Look at the leopard danio! 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. 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 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 house one male with one or two females for company. A female will have a smaller dorsal fin and a pinkish belly. There are blue spangles in the black spot to her side. 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 show parental care for their young. The male is shown on the left and the female on the right in this photo.
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 animals that prefer to swim in the middle and top of an aquarium.
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 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. Baby brine shrimp can be used as fry food. Find out more about Apistogramma in our Apistogramma care manual.
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 Panda is a smaller species than larger cory catfish. It can grow to 1.75 to 2.25 inches in length. This means that you can easily keep six of them in a 20-gallon tank. 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. 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
This smaller rainbowfish is known for its piercing blue eyes, bright yellow body, and spotted finnage. When you have six or more males, they will display their fins in a showy dance to attract attention. The spotted blue-eye rainbowfish is our favorite because of its unique appearance and interesting behavior. They can be difficult to find and are more expensive depending on where you live. However, if you have a plant tank with them, or a background of black, they will take your breath away.
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.
Subscribe to our newsletter if you like articles such as these! Each week, we send out an email with a summary and links to all of our blog posts, videos, live streams, and videos.