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. Provide them with lots of rockwork to simulate their natural habitat, and they’ll feel right at home. 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. 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. The great thing about these danios is how resilient they are – they can live at room temperature without a heater and are happy in a wide range of pH and water hardness. Get a group of six, and watch them speed around the top third of the fish tank. To prevent them from hogging all the food, pair them with other fast, midwater fish like tetras and rasboras for a highly entertaining aquarium.
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. On the other hand, a male is larger and has a longer dorsal Ray. There are no blue spangles in his black spot. Keep in mind that the South American dwarf cichlid prefers temperatures above 85 degrees F. So keep them around other hot water fish such as cardinal tetras or Sterbai cory catfish.
German blue Rams are monogamous, and have a tendency to show parental love 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. The fish’s distinctive triangular black pattern and bright orange coloration stand out in a beautifully planted tank. The fish can grow to two inches in length and is easy to care for. You can find more information in our care guide on 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. Baby brine shrimp can be used as fry food. Find out more about Apistogramma in our Apistogramma care manual.
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. To scavenge their favorite foods such as Repashy gel food and frozen bloodworms, they use the whiskers or barbels around their mouths. 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 favourite because of their distinctive black and white coloration.
1. Pseudomugil gertrudae
This smaller rainbowfish is well-known for its bright yellow body and brilliant blue eyes. When you have six or more males, they will display their fins in a showy dance to attract attention. We chose the spotted blue-eye rainbowfish as our number one pick because of their colorful appearance, interesting behavior, and uniqueness in the hobby. 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 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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