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.
If you have ever dreamed of keeping Tanganyikan Cichlids, this stunning fish of three inches is the right choice. Their amazing ability to swim vertically or sideways and upside down allows them to be close to hiding spots and surfaces. They will feel at home if you provide them with plenty of rockwork that simulates their natural habitat. 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. Julies are peaceful fish, and they can live with other African cichlids.
Julidochromis, or the golden Julie, is a popular variety because of its vibrant 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! This brightly spotted schooling fish looks like a little trout and comes in both short and long fin varieties. 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. Take six of them and watch their speeding around the tank’s top. 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 daanios can be a cost-effective and easy way to school fish. They aren’t as common as their more famous cousin, 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 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. It is important to keep in mind that this South American dwarf catfish prefers higher temperatures, around 85°F.
German blue rams form monogamous pairs that show parental care over 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. Our full care guide provides more information about caring for rasboras.
Harlequin rasboras are social creatures that tend to swim in the middle to top sections of an aquarium.
Apistogramma cacatuoides, and Apistogramma gagassizii are the two most common members of this large genus 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. You can help her by providing baby brine shrimp for fry food, and making sure the water quality is as good as it can be. You can learn more about them in the Apistogramma Care Guide.
This male Apistogramma cacatuoides has long, brightly colored dorsal fins, whereas his female counterpart is smaller in size and turns yellow during spawning.
2. Panda Corydoras
Corydoras can be kept in 20 gallon tanks. They are smaller than the larger cory catfish species. This peaceful bottom dweller can be kept in cooler temperatures from 72 to 77degF. They use the barbels or whiskers around their mouth to scavenge for their favorite foods, such as frozen bloodworms and Repashy gel food. If you keep them happy and well-fed, you might soon see breeding behavior and sticky eggs covering your 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 known for its piercing blue eyes, bright yellow body, and spotted finnage. If you get a group of six or more with both genders, the males will compete for attention by displaying their beautiful fins in 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, you’ll be amazed at their beauty.
You can encourage rainbowfish to lay eggs by using spawning mops made of yarn. Then, remove the mop and place the fry in separate tanks.
If you enjoy articles like this, don’t forget to sign up for our newsletter to receive a weekly email with a summary of all our latest blog posts, videos, and live streams!