Most Popular Fish for 20-gallon Tanks

Top 10 Most Popular Fish for 20-gallon Tanks

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With aquariums, size is really an important factor. Fish tank size will often show the species of fish you can raise in your tank and the number of fish. 

You will want to ensure you have the right aquarium for the fish you’re going to keep. A 20-gallon aquarium is large enough to build into a beautiful and enjoyable tank that contains gorgeous and interesting fish. 

In this article, we’ll introduce the most popular types of fish for 20-gallon tanks. Let’s dive right in! 

How Many Fish Can You Raise in a 20-gallon Tank? 

The number of fish that can live in your 20-gallon aquarium depends on the species of these fish. Fish size, water requirements, and temperament are critical factors that decide how many fish you can raise in a tank. Generally, the rule in raising fish is one gallon of water per inch of fish. 

Bear in mind that putting the wrong fish in the wrong-sized aquarium can make the tank challenging to maintain and, in some cases, get your fish sick or maimed. 

Types of Fish for 20-gallon Tanks 

1. Hatchetfish 


Hatchetfish are little funny fish for 20-gallon tanks. The oddly-shaped hatchetfish is native to South America and can be found in Venezuela, Peru, and The Guianas. 

These fish are peaceful and get on with non-aggressive creatures. They will spend most of their time swimming near the upper part of the aquarium around the water surface. 

Hatchetfish are carnivorous species. You can feed them with protein-rich flakes, bloodworms, brine shrimp, and other fish food. 

2. Zebrafish 


This freshwater fish originates from South Asia, which is well known for its regenerative abilities.

In the natural habitat, Zebrafish are silver-gold with 5 stripes from their head to their caudal fins. The males are more golden-colored relative to the more silvery-white females. 

Zebrafish are very peaceful and social, sometimes living in schools, with an established hierarchical system. Therefore, make sure you don’t leave them alone in the tank because they might be stressed and hide all the time. 

Remember that they may become aggressive, particular when kept with slow-moving long-finned fish species. 

3. Goldfish 


One of the most suitable fish for 20-gallon tanks and one of the most prominent tank fish, this small member of the carp family comes from East Asia. The common goldfish has many colors, including red, gold, white, orange, black, or yellow. 

Goldfish are an overall peaceful species, with some displays of schooling behavior. They might compete for food, but don’t hurt each other. 

You can pair these fish with similar body types and swimming characteristics, such as rosy barbs, Banded Corydoras, Platies, or Zebra Danios. 

4. Electric Blue Ram

Electric Blue Ram
Electric Blue Ram

Electric Blue Rams are native to South America, specifically in the freshwater bodies of Venezuela and Colombia. These fish are well known for their unique eyes and stunning colors. Depending on how the light hits them, their blue color can have different shades. 

These creatures are omnivores. In the wild, they often roam around the waters foraging for plant and animal matter. In aquariums, you can feed Blue Rams anything as they are not picky eaters. The fish prefer sinking algae pellets, frozen bloodworms, frozen brine shrimp, and freeze-dried bloodworms.

5. Zebra Danios 

Zebra Danio
Zebra Danio

Zebra Danios are great fish for 20-gallon tanks. They are indigenous to Southeast Asia, specifically in the freshwater bodies of Pakistan, Bangladesh, and the Ganges and Brahmaputra rivers. 

They are peaceful species and perfect for community aquariums. That said, they are also nippers who might go after some types of fish with large fins. These fish include angelfish or guppies. So be careful when picking tank mates for Zebra Danios. 

These creatures are omnivorous and will consume algae, larva, worms, and small crustaceans in natural environments. In aquarium, you can provide the fish with high-quality fish flakes, sinking pellets, and bloodworms. 

6. Swordtail


Swordtails are among the most common live-bearing fish that are easy to maintain in a community tank. They feature a sword-like appearance that makes them appealing to viewers. 

It is simple to care for these fish. They will grow well in a broad range of conditions but prefer much light and live plants to hide from predators. 

Swordtails are relatively active bottom feeders. They typically eat nearly anything you give them and can be trained to take food from your hand. They can consume bread, pellets, flakes, bloodworms, and even brine shrimp. 

These critters love soft water with a slightly acidic pH level of 6-7. They will live happily when kept in groups of at least six individuals. 

7. Leopard Danio 

Leopard Danio
Leopard Danio

Coming from the Danionidae family, these small fish have an average lifespan of 2 years. They only develop up to 1.5 inches long, making Leopard Danios perfect fish for 20-gallon tanks. 

The fish feature a blackish body with leopard-like spots along their sides with visible fins and red eyes. They love eating mosquito larvae, bloodworms, brine shrimp, and daphnia. 

They are peaceful and docile. You can keep them in schools of six or more, and house them with other peaceful fish like mollies and guppies. 

The fish require a lot of space to swim and play round. Remember to keep them away from direct sunlight. Besides, Leopard Danios might get sick easily if water parameters are not properly maintained.

8. Panda Corydoras

Panda Corydoras
Panda Corydoras

Unlike bigger species of cory catfish, Panda Corydoras only reach 1.75 to 2 inches long, so you can keep a group of six fish for 20-gallon tanks. 

These friendly bottom dwellers can be kept in cooler temperatures from 72 to 77 degrees Fahrenheit. 

They often use their barbels or whiskers around the mouth to look for food. You can feed them with frozen bloodworm or gel food. If well-fed and well-treated, Panda Corydoras will easily breed and lay sticky eggs over the tank walls. 

9. Molly Fish 

Molly Fish
Molly Fish

Mollies are great fish for 20-gallon tanks. They hail from coastal areas in the United States and Mexico. These fish come in a wide array of colors, including black, white, and orange. 

Being peaceful and well-behaved, Molly fish thrive well in a community tank with other non-aggressive species. You should keep them away from aggressive mates like puffers, crayfish or bettas. 

These creatures are omnivores who love consuming vegetables or sinking wafers. If you want to change their diet some time, they have no problem consuming bloodworms. 

10. Bristlenose Pleco

Bristlenose Pleco
Bristlenose Pleco

Bristlenose Plecos are interesting-looking species. They are indigenous to South America and can be found in the Amazon River Basin. They are well known for cleaning up algae in fish tanks. 

These pets can grow up to 3-5 inches long, so it makes them suitable fish for 20-gallon tanks. However, you should only have one in your tank because the fish can be a bit territorial, particularly with two males.

The fish are mostly herbivores. They can eat a lot of food but prefer plant-based one. You can provide them with spirulina, vegetables, and sinking algae pellets. 


That’s the list of suitable fish for 20-gallon tanks. Bear in mind that do careful research on each species before introducing it to your aquarium. 

One crucial thing you must not forget is that you need to cycle your tank first before adding any new fish to the tank. Without good cycling, your fish might die. 

Learn more:

Top 10 Best Fish for 5-gallon Tanks

12 Best Fish for 10-gallon Tanks

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