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Fish Tank Sizes (Charts & Tables)

A photo colage of a fish tank in various sizes.

Fish tanks are a wonderful way to bring some nature, life, and enjoyment into your home. Fish, reptiles, rodents, and corals can all be kept in fish tanks. These are all great options for people who want a quiet, hypoallergenic pet.

Deciding on an aquarium size can be difficult, as so many fish tank sizes and shapes are available to consumers. Below we’ll take a closer look at the various fish tank sizes available so that you can find the perfect fish tank size for your home.

Related: Types of Molly Fish

Choosing a Shape

Chart of Different Fish Tank Shapes

One of the best features of a fish tank is that there are endless shapes and sizes available. Selecting a different fish tank shape can help add interest to your room or better suit the pet you intend to keep.

Different fish tank shapes may be better for freshwater fish or saltwater fish or may suit a rodent or reptile better. Before choosing any fish tank, it is essential to measure your available space and think about the pet you want to house in the tank.

Rectangle Fish Tank Sizes (Illustrated)

1. Large Rectangle Fish Tank Sizes (Diagram)

Large rectangle fish aquarium sizes (diagram)

2. Mid-Sized Rectangle Fish Aquarium Sizes (Diagram)

Mid-Sized Rectangle Fish Aquarium Sizes (Diagram)

3. Small Rectangle Fish Tank Sizes (Diagram)

Small Rectangle Fish Tank Sizes (Diagram)

Specialty Aquarium Sizes

1/2 Cylinder Shape Aquarium Tank

Chart of a 1/2 Cylinder Shape Fish Tank Sizes

A half-cylinder-shaped aquarium is a perfect way to add motion to a room. This shape of tank tends to be larger than others, beginning at the capacity of about a 60-gallon tank. This tank also tends to be tall and slender.

Before choosing fish to put in a half-cylinder tank, make sure there is a strong enough light so that light can reach the bottom of the tank. Placing live plants or corals in such a tall and deep tank can be tricky if only a weak light is used to support life inside the half-cylinder aquarium.

1/4 Cylinder Shape Aquarium Tank

Chart of a 1/4 Cylinder Shape Fish Tank Sizes

Adding a one-fourth cylinder-shaped aquarium still gives the feel of a rounded front aquarium, but is only one-fourth of the cylinder shape. This size fish tank is perfect for placing in a corner of a room.

The one-fourth cylinder comes in capacities as small as 50 gallons, making this an ideal medium-size tank. It is possible to get a one-fourth cylinder tank with a capacity of up to 150 gallons. This size one-fourth cylinder tank is perfect for maintaining a suitable reef aquarium.

Bow Front UV Aquarium Tank

Chart of a Bow Front UV Fish Tank Sizes

Many pet owners choose to purchase a bow front shape aquarium. This type of aquarium tank is shaped like a rectangle with a bowed front. The rectangular shape of this aquarium, with its bowed front, can add a great deal of interest and dimension to a fish tank.

Bow front tanks tend to be large, ranging in capacity from 65 gallons to 190 gallons. This type of tank works well for either freshwater or saltwater fish but does tend to distort the look of fish, plants, and corals because of the bowed front. However, a bow-front tank may be an excellent choice for reptiles or rodents.

Fish Tank Breeder Aquarium Tank

Chart of a Fish Tank Breeder Sizes

Traditionally used as a tank to breed aquarium fish, the breeder-size aquarium tank comes in 30-gallon or 40-gallon sizes. These tanks tend to be low and long in shape, making them great for many different types of hobbyists.

The breeder tank is also perfect for reptiles who do not need a particularly tall tank but do require plenty of surface area to explore and roam. Many owners choose to use a breeder tank as a sump tank for a more extensive aquarium system.

Flat Back Hexagon Aquarium Tank

Chart of a Flat Back Hexagon Fish Tank Sizes

Just as the name implies, the flat back hexagon aquarium tank shape is a hexagon with a flat back. This tank has an ideal shape due to the fact that it can fit flush against a wall, making a minimal footprint in your room.

Flat-back hexagon tanks also come in a range of sizes, available from the small 30-gallon tank or the large 150-gallon tank. Many larger flat-back hexagon tanks can be quite deep, so it is important to use a light strong enough that light can reach the tank’s bottom if you plan to keep live plants or corals in it.

Hexagon Aquarium Tank

Chart of a Hexagon Fish Tank Sizes

The hexagon shape aquarium tank is ideal for most because it comes in such a vast range of sizes. Small hexagon tanks can have a capacity of just 20 gallons, while larger varieties can hold up to 105 gallons. This tank appeals to many people because of its interesting and elaborate design.

Hexagon tanks are beautiful to look at but can distort how fish appear, due to their many angles and facets. Also, hexagon aquarium tanks can be difficult to clean, as algae and debris easily collect in the many corners of this aquarium.

Pentagon Aquarium Tank

Chart of a Pentagon Fish Tank Sizes

The pentagon aquarium tank is a nice shape for those who desire or require a mid-size to a large aquarium. A pentagon aquarium tank gives a similar look to that of a hexagon tank but has a bow front whereas a hexagon tank does not.

This tank is perfect for corners of rooms and has a minimal footprint. Also, with the pentagon tank’s flat front face, fish and livestock are less distorted. The pentagon aquarium shape makes it an easy task to clean, but still adds plenty of visual interest wherever it sits.

Rectangular Aquarium Tank with Square Corner

Chart of a Rectangle with Square Corner Fish Tank Sizes

Intended for huge fish tanks, the rectangular tank with square corners is a professional-grade tank. Often, these tanks are sold as acrylic aquariums due to their large size. The acrylic can help reduce the overall weight of the tank.

The rectangular aquarium tank with a square corner can be used for either freshwater or saltwater aquariums and allows hobbyists to create any underwater landscape that they can dream up.

Rectangle Aquarium Tank

Chart of Rectangle Aquariums Fish Tank Sizes

A rectangular tank is the most common type of aquarium found in homes. This tank is a perfect home for reptiles, rodents, saltwater fish, or freshwater animals. The rectangular aquarium tank comes in many sizes.

A small ten-gallon tank is perfect for most beginning hobbyists. Rectangular tanks are easy to clean. It is also easy to find available stands in various styles to go with the fish tank.

Aquarium Size

Choosing the right size aquarium for your home can be tricky. There are plenty of sizes available on the market, and the size you choose will help determine if you can keep a betta tank, a neon tetra, or something larger.

The tank’s size will be important when considering the weight consideration and the various filters, heaters, lighting, and accessories needed. A larger tank will require larger equipment, which can be more costly.

Small Aquariums

Chart of Small Aquariums Fish Tank Sizes

Generally speaking, small aquariums range in capacity from 2.5 gallons to about 15 gallons. These tanks can come in many shapes and dimensions. A 2.5-gallon tank may be perfect as a betta tank, or for housing a hermit crab.

An aquarium with a capacity of about 10 gallons can be excellent for housing small reptiles or rodents, or for use as a community fish tank. A 15-gallon tank may house small tropical fish, such as a neon tetra or a few mollies. A fifteen-gallon aquarium has small dimensions, but an expert hobbyist may create a nano-reef in this tank size.

Medium Size Aquariums

Chart of Mid-Sized Aquariums Fish Tank Sizes

A medium size tank is considered to have a capacity in the range of 20-40 gallons. There are plenty of pets that can be kept in a tank this size. Often the equipment associated with a mid-size tank can be quite affordable.

A mid-size tank can come in several different shapes and sizes and is perfect for fresh or saltwater fish. Many mid-size tanks also come in an aquarium kit with the proper lighting, filtration, and aquarium decorations ready to go. A 20-gallon tank is perfect for housing multiple small rodents, like mice, or can be used to house a snake or small lizard.

Large Aquariums

Chart of Large Aquariums Fish Tank Sizes

Large aquariums have quite the size range, varying from about 50 gallons to 180 gallons. These tanks generally tend to come in simpler shapes, like bow fronts and rectangles.

Larger tanks are often necessary to house more complex saltwater setups, such as those that require plenty of swimming room for marine fish. These tanks are beautiful, but heavy. Be sure to calculate the tank’s total finished weight once rock, sand, and water have been added to it.

Fish Tanks Over 100 Gallons in Capacity

Chart of Fish Tanks Over 100 Gallons

Large fish tanks over 100 gallons are beautiful, but require plenty of work. No matter whether you intend to keep a saltwater or freshwater aquarium, you must be prepared to purchase extensive equipment and put in a lot of labor.

Finding filters, pumps, lighting, and heaters for aquariums over 100 gallons can be difficult, and prices for these aquarium essentials can be quite high. Large aquariums also require plenty of structural reinforcements within the home where they are located.

Be sure to consider these tanks’ placement in space, and try to center the weight over a beam or other support in your home.

Choosing the Right Aquarium Size

Before selecting the right size fish tank for your needs, you must think carefully about what you plan to do with your fish tank. It can help to speak with professionals at a pet store to understand the size requirements of certain animals.

Before purchasing the animal, make sure you have the right setup in place to house it. This means having a correctly sized aquarium and having the right equipment to run the fish tank size of your choice.

Choosing the right size aquarium also means considering how much time and effort you are willing to dedicate to taking care of it and the life inside it. Having a large tank can mean more money spent on equipment and more time performing water changes and cleaning. Smaller tanks are not necessarily easier, though.

Because there is less water in a small tank, water quality degradation occurs much more quickly, requiring smaller water changes more frequently. Think about the available space in your home and where you want the tank to go, as well. Choosing the right tank is all about balancing expectations, time commitment, and the animals planned to house in it.


We know that choosing the right fish tank for your home can be tricky. There are so many considerations to keep in mind, and so many different options available on the market. To help, we have put together a list of the most commonly asked questions about fish tank sizes so that you can choose the right aquarium for your home.

Where to put your fish tank?

A fish tank can be incredibly heavy, and even more so when water is added to the tank. It’s safest to assume that every gallon of space in an aquarium will weigh about 10 pounds once water, rock, gravel, and sand are added to it. This means that a five-gallon fish tank can weigh close to 50 pounds.

Think about what areas of your home can support this significant amount of weight before setting up a fish tank. Before placing your fish tank, be sure to choose a place that will stay for a long time. Moving a fish tank requires removing the fish, plants, and water, which is a disruptive process.

Can a fish tank be too large?

Yes! A fish tank can be too large, especially if the space or time is not available to dedicate to the hobby. Having too large of a fish tank can draw too much time and energy away from other activities and hobbies you may enjoy.

While the fish and other inhabitants of an aquarium would undoubtedly appreciate more room to swim or roam, they most certainly will not appreciate dirty water constantly.

Do you have too many fish in your tank?

Overcrowded fish tanks are a real problem with which many people struggle. Owning a fish tank is about creating and maintaining a delicate ecosystem. Many water parameters and levels must remain exactly in check to foster a thriving environment.

Fish are dirty animals that release toxins, like nitrates, into the water where they live. Further, feeding fish can cause excessive water pollution. If toxin levels get too high from spiking nitrates or ammonia, it can cause fish to die. Always be sure to check with a local fish or pet store about the amount of fish that can live in the tank size you have.

A general rule to follow is that freshwater fish need about one gallon of space per inch of fish. Marine fish require about three to five gallons of space for every inch of fish.

Can saltwater and freshwater fish live in the same tank?

No, freshwater fish and saltwater fish have very different needs related to the type of water where they can live. Freshwater fish require fresh water. This type of fish usually includes several tropical fish varieties. On the other hand, saltwater, or marine, fish require water that is mixed with ocean salt.

What fish can go in a five-gallon tank?

A five-gallon tank is the perfect size tank for small, tropical freshwater fish. A five-gallon tank can happily house a betta fish or some small danios or tetras. African dwarf frogs are happy to live in a 5-gallon tank, and can even have some tank mates like a molly or platy.

Guppies, which come in a range of colors and patterns, are also perfect for a five-gallon tank. Remember, it is good practice to have about five inches of fish total living in a five-gallon aquarium.