How Big is A 20-gallon Fish Tank? Explained

Lauren Kiekbusch
What Size is a 20-Gallon Fish Tank

As an experienced fishkeeper, I’ve learned that selecting the right aquarium size is crucial for the health and happiness of your aquatic pets. Today, I want to share my insights specifically about 20-gallon tanks, a popular choice among both beginners and seasoned hobbyists.

A 20-gallon fish tank strikes a balance between space and manageability, making it a versatile option for various fish and plant species. Whether you’re setting up your first home aquarium or looking to add another tank to your collection, understanding the dimensions, capabilities, and care requirements of a 20-gallon tank is essential.

In this guide, we’ll explore everything you need to know about 20-gallon fish tanks. From their standard dimensions to the types of aquatic life they can support, lets get started.

What Size is a 20-Gallon Fish Tank

20-Gallon Tank Size Dimensions and Comparison

Standard Dimensions of a 20-Gallon Tank

A standard 20-gallon fish tank typically measures around 24 inches in length, 12 inches in width, and 16 inches in height. However, these dimensions can vary slightly depending on the manufacturer and the style of the tank.

It’s important to note that there are generally two types of 20-gallon tanks – the 20-gallon long and the 20-gallon high. The 20-gallon long tank is wider and provides more horizontal swimming space, ideal for certain types of fish, while the 20-gallon high tank is taller, offering more vertical space.

Comparison with Smaller and Larger Tanks

Compared to smaller tanks, like the popular 10-gallon size which usually measures 20 inches in length, 10 inches in width, and 12 inches in height, the 20-gallon tank offers double the water volume. This extra space provides more room for fish to swim and allows for a greater variety of fish and plant life. It also helps maintain a more stable environment, as larger volumes of water are less susceptible to rapid changes in parameters like temperature and pH.

In contrast, larger tanks such as a 40-gallon tank, which often measures around 36 inches in length, 18 inches in width, and 16 inches in height, offer even more space and diversity in terms of fish and plant species you can keep. However, larger tanks require more maintenance, more equipment, and of course, more space in your home.

Choosing the right size tank depends on your space availability, the type of fish you want to keep, and the amount of maintenance you’re willing to undertake. A 20-gallon tank offers a great middle ground, providing ample space for a variety of fish and plants while still being manageable in terms of maintenance and space requirements.

20-Gallon Fish Tank size

Best 20-gallon Fish Tanks to Buy

Here are the best 20-gallon fish tanks on the market today, as recommended by the FishTrivia team.

What’s The Best Fish for 20 Gallon Fish Tank?

Usually, small to moderate fish carry in 20 gallons ranging from nil to about 4.5 centimeters or often up to 6 centimeters. Moreover, you can have to go for a somewhat larger tank if you want a group. Same for holding organisms in kindergarten.

1. Killi Fish

Killi Fish
  1. Size: 0.7 to 3.5 inches
  2. Minimum Tank Size: 20 gallons per pair
  3. Care Level: Easy to Difficult (depending on the species)
  4. Temperament: Mostly peaceful
  5. Tank Conditions: Depends on the species

Killifish are colorful, freshwater fish in stunning designs and are one of the most common fish in household aquariums. They enjoy living foods in the tank, but also flake foods including frozen shrimp and bloodworms. 

While they are perfect for group tanks, they do have some difficult requirements for killifish and the need for cooler temperatures. They are native to the tropical rainforest and habitat swimming pools, swamps, and streams, and the others live in tropical savannah swimming pools (more popular). 

Yet, even in the wild, all killifish are thin, so you can be confident that they will match your tank of 20 gallons.

2. Kuhli Loach

Kuhli Loach
  1. Size: 3 to 4.5 inches
  2. Minimum Tank Size: 20 gallons
  3. Care Level; Easy to Moderate
  4. Temperament: Peaceful
  5. Tank Conditions: 75°F to 85°F, ph 6 to 7

The Kuhli loaches are widely recognized in Indonesia, Malaysia, Java, and the surrounding region as tropical waters. 

It is an unusual fish with eel-shaped bodies like salmon pink or yellow, dark brown to black stripe, and half-round the tail. Usually, Kuhli loaches are 3 to 5 inches long, so good candidates for a 20-gallon aquarium with a light bioload have to be sought. 

Coolie loaches are scavengers and receive significant food by digging the remains. But it is not meant to mean that they can survive on scraps, so incorporate pellets and a number of live meals into their diet.

3. Tiger Barbs

Tiger Barbs fish
  1. Size: 2.8 to 3.9 inches
  2. Minimum Tank Size: 20 gallons
  3. Care Level: Easy
  4. Temperament: Aggressive
  5. Tank Conditions: 68°F to 80°F, water hardness (5 to 19 dGH), ph 6.0 to 8.0

Tiger barbs are an outstanding addition to many tanks and are easy to look after. They are also lovely in yellow, green, golden-red, and black lines of background color. 

Though tiger barbs are seminary and established nippers, they still make fine fish from the population and love swimming in schools. These barbs expand up to a length of 2.7 inches and thus are suitable to hold in an environment of 20 gallons. 

The healthy food for tiger barbs includes tropical flakes, sage-cured shrimp and other small crustaceans, daphnia, glass worms, and blood worms. Feed them, if you may, twice a day or once a day. In addition, use a high-quality flake food that is primarily the basic meal for most types of aquariums.

4. Zebra Danio

Zebra Danio
  1. Size: 2.5 inches
  2. Minimum Tank Size: 10 gallons
  3. Care Level: Easy
  4. Temperament: Peaceful (although mildly nippy)
  5. Tank Conditions: 65°F to 77°F, ph 6.5 to 7.2

The freshwater fish of the miniature family originating in South Asia are Zebra Danios, also known as zebrafish or Danio rerio. Danio Rerios grow to an average of 2.5 inches, so in your 20-gallon you can comfortably carry them. However, they are a genus that must be contained in a group. 

In addition, zebrafish are tolerant of colder weather, and will hence live in a heater-less tank and make good friends in goldfish ponds. Zebra danios aren’t what you’re supposed to call fussy eaters and almost devour everything you sell them.

5. Platies

platy fish
  1. Size: 1.5 inches (male), 4.8 inches (female)
  2. Minimum Tank Size: 20 gallons
  3. Care Levels: Easy
  4. Temperament: Peaceful
  5. Tank Conditions: 70°F to 75°F, hard water (10 to 20dGH), ph 6.8 to 8

Platies are another common living alternative that is closely associated with mollies. They were born in Central and Southern Mexico on the East Coast. 

The fish are robust and lively, and complement the aquariums of the city. The plate is also quick to breed through intensive selective breeding with new color varieties. 

These livebearers are very adaptive to a large variety of water conditions, but they can contribute to distress and search for abrupt shifts in water parameters. 

They enjoy challenging water like much other fish and enjoy plant tanks with plenty of secret gaps as well as plenty of swimming areas. Platies are known as omnivores, although there is a significant criterion for herbivores.

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