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10 Gallon vs 20 Gallon Fish Tank: The Main Differences (With Pictures)

Sarah Psaradelis

By Sarah Psaradelis

10 vs 20 gallon fish tank header

Fish tanks are available in various sizes, but the 10- and 20-gallon fish tanks are amongst the most popular in the hobby. Both tanks are quite similar, with the main difference being in the size of the fish tank which influences the type and number of fish you can keep inside.

Fish keeping should be fun, so choosing an aquarium is fairly simple once you understand the differences between each fish tank size and how they can benefit you and the livestock you plan to keep inside.

If you are having difficulty choosing between either a 10- or 20-gallon aquarium, then this comparison article can help you make a more informed choice.

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At A Glance

10-Gallon Fish Tank
  • Convenient
  • Lighter and desk-friendly
  • Less quantity of livestock
  • Ideal for nano fish or invertebrates
20-Gallon Fish Tank
  • Good for beginners
  • More space for livestock
  • Ideal for a larger variety of fish and livestock

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Overview of 10-Gallon Fish Tanks

Different Types

The 10-gallon fish tank is available in different shapes and designs, and it can have more vertical or horizontal space depending on the type of fish tank you like best. You can get tall 10-gallon fish tanks that have more vertical space, which is a good choice for smaller spaces and fish species that need more vertical than horizontal space.

These fish tanks are also available in different shapes, such as hexagonal, rounded, or corner tanks. The type of 10-gallon fish tank you choose is down to your personal preference, along with what types of fish you would like to keep inside.

Ten-gallon fish tanks can also be made of different materials, such as standard glass, iron glass, or durable acrylic. These materials can influence how clear and strong the aquarium is, with each type of material ranging in price.

A small 10 gallon fish tank on a wooden surface
Image Credit: Ja Crispy, Shutterstock

Space & Placement Considerations

Unlike larger aquariums that require more consideration to their placement and space because of the tank’s weight and large surface area, 10 gallons are more practical.

The 10-gallon small size makes it easier to find a space in the house to put this fish tank, such as on a desk or countertop. However, since the fish tank will become heavier when it is filled with water and weigh around 110 pounds, you will need to ensure that the counter you place the tank onto is strong enough to support the weight.

Maintenance Requirements

Smaller tanks can be easy to maintain, although there is less room for error in such a concentrated space. This means that the inhabitant’s waste and tank pollution can affect the fish or invertebrates quicker than in a larger fish tank where the waste is more diluted. So, smaller fish tanks might take some more work to maintain, and you will need to keep up with regular water changes, water testing, and keeping the water aerated.

Water changes are necessary for most tanks, and freshwater helps remove and dilute excess fish waste that isn’t used by the filter.


What Can You Stock This Fish Tank With?

When it comes to stocking a 10-gallon aquarium, your choices of fish are limited due to the size of the tank. Most fish require a larger minimum tank size, so you will have to choose small fish that don’t require much space.

Keep in mind that 10-gallon fish tanks are too small for fish like goldfish and cichlids that thrive in larger tanks with more room to grow and a larger water volume to dilute their waste from building up.

So, when it comes to stocking a 10-gallon fish tank, you can choose from small tropical fish like bettas and guppies, or invertebrates such as mystery snails and shrimp. You can also stock 10-gallon fish tanks with live plants, which not only makes the aquarium look nice and naturalistic but can help benefit the 10-gallon fish tanks’ water quality and inhabitants.

  • Cheaper option
  • Convenient for small spaces
  • Available in different shapes and designs
  • Ideal for nano fish
  • Lightweight
  • Less stocking options
  • Limited space for fish and plants
  • Too small for most plants, fish, and invertebrates

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Overview of 20-Gallon Fish Tanks

Different Types

Even though the 20-gallon fish tank is double the size of the 10-gallon, it is still available in different shapes and designs. Twenty-gallon aquariums are available in tall designs or long designs. These tanks differ in terms of the amount of vertical or horizontal space they offer.

You get 20-gallon fish tanks that are in hexagonal shapes, rounded, squared, rectangular, and even large corner aquariums. Like the 10-gallon fish tank, the 20-gallon is available in acrylic, iron, or standard glass depending on your preference.

Tetra ColorFusion Aquarium 20 Gallon Fish Tank Kit

Space & Placement Considerations

Since the 20-gallon fish tank is larger, you will need to make space arrangements, as this tank will take up more room while being heavier. This means that a 20-gallon aquarium is likely going to be too big for your desk or a side table, and it will be better to place it on a stand that can support the fish tank’s weight and size.

If the average 20-gallon aquarium weighs around 225 pounds when filled with water, the fish tank stand you use should be reinforced to withstand the weight of the tank to prevent it from breaking or cracking. It is also important to ensure that the sides of the fish tank do not overlap off the fish tank stand, as this can put pressure on the aquarium leading to leaks and breaking.

Maintenance Requirements

The 20-gallon fish tank is quite easy to maintain, which is why it is recommended for beginners. It is not too large to the point where cleaning becomes difficult while having a larger volume of water.

Although the 20-gallon is bigger, the maintenance of this tank is relatively the same as a 10-gallon, with the exception that any waste from fish and other tank inhabitants is not as concentrated if the tank is stocked appropriately.

You will need to do regular water changes and tests to monitor the fish tank’s water quality.

Tetra Aquarium 20 Gallon Fish Tank Kit

What Can You Stock This Fish Tank With?

You have more options when it comes to stocking a 20-gallon aquarium than a 10-gallon aquarium. The larger volume of water makes it suitable for a variety of different fish, giving you more options than if you were to choose a 10-gallon fish tank. However, there isn’t much of a difference in the stocking quantity of a 20-gallon, as you don’t want to overstock your fish tank but rather the species of fish you can keep inside.

A 20-gallon fish tank can house a single baby fancy goldfish, small schooling fish like neon tetras, or larger fish like dwarf gourami and livebearers such as molly and platyfish. These tanks are also suitable for snails and shrimp, and you get to stock them with more invertebrates due to the larger volume of water.

  • Available in different shapes
  • Able to house a larger quantity of fish
  • Ideal for beginners
  • Easy to maintain
  • Needs a strong base to protect the weight of the tank
  • Difficult to move around

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Other Factors to Consider

If you are still having difficulty choosing between a 10-gallon and 20-gallon fish tank, these are other factors to consider:

The Price

Depending on the design and type of 10-gallon you buy, they are usually cheaper than a 20-gallon. Since the 20-gallon fish tank is larger, it will be priced higher. However, the price difference between a 10-gallon and a 20-gallon aquarium is not too drastic, and they are within a similar price range. If the fish tank includes a kit, such as a filter, heater, and gravel, the price will be higher than a plain fish tank.

Aquarium Equipment & Decoration

The type of aquarium equipment and decorations you plan to put inside the fish tank will influence which sized tank is the better option. Keep in mind that aquarium equipment such as heaters, filters, and aeration systems take up space in a fish tank, thus reducing the amount of swim space for your fish.

So, if you plan to use a large filter and use large decorations in the tank, then the 20-gallon will be the better option since it offers you more space. Large decorations and aquarium equipment in a small aquarium can look cramped, which can affect the overall appearance of the tank.

Final Thoughts

Overall, both the 10- and 20-gallon fish tanks are good, but the tank you choose will depend on what types of fish you want to put inside since there is a 10-gallon difference between each one. If you want to keep larger fish or perhaps a small community of suitable fish in a fish tank, then the 20-gallon fish tank is the better option. Whereas if you want to keep a betta fish and some snails or shrimp in a small tank, then the 10-gallon fish tank is the better choice.

Featured Image Credit: (Left) JBJ Rimless (Right) Tetra ColorFusion

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