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.
If you have ever dreamed of keeping Tanganyikan Cichlids, this stunning fish of three inches is the right choice. 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 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. 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 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. Get a group of six, and watch them speed around the top third of the fish tank. 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
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 fin, pinkish belly, and blue spangles inside the black spot on the side of her body. The male is bigger, has a longer dorsal fin, pinkish belly, and blue spangles within her 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 is another popular schooling fish that does great in a group of six to eight. In a well-tended tank, their distinctive black triangular pattern and bright orange coloration make them stand out. 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 are social creatures that tend to swim in the middle to top sections of an aquarium.
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. The female will marry her male if you have breeding caves. This will help protect her eggs and provide care for the young. Help her out by offering baby brine shrimp as fry food and keeping the water quality as clean as possible. 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
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. You can keep this calm bottom dweller in temperatures between 72 and 77°F. They use the barbels or whiskers around their mouth to scavenge for their favorite foods, such as frozen bloodworms and Repashy gel food. 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 panda cory catfish are popular for their unique black-white coloration.
1. Pseudomugil gertrudae
This smaller rainbowfish is well-known for its bright yellow body and brilliant blue eyes. 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. 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 can encourage rainbowfish to lay eggs by using spawning mops made of yarn. Then, remove the mop and place the fry in separate tanks.
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