Fish Tank Sizes & Types: How to Choose the Right Aquarium
Learn how to give your fish a happy, healthy home.
Well-designed aquariums can be gorgeous, dynamic additions to your home decor while also serving as the perfect home for your aquatic pets. Because the fish tank you choose will be the sole habitat for all of your fish, it's crucial to understand how aquarium dimensions can impact the health and quality of life of your fish. In this guide, we explain fish tank sizes so you can make the most educated decision possible.
Fish Tank Sizes
Fish Tank Sizes & Corresponding Weights
Which Type of Fish Tank Should I Choose?
Saltwater vs. Freshwater
Which Fish Tank Material is Best?
Fish Tank Sizes
Here is an overview of size options for fish tanks based on their gallon capacities.
Up to 10 Gallons
Professionals recommend 5-gallon tanks as the minimum aquarium size for just one fish. This prevents fluctuations in pH and prevents buildups of potentially harmful chemicals or waste materials. They also ensure a healthy gas exchange and give the fish enough room to swim and live a happy, healthy aquatic life.
Small aquarium sizes below 5 gallons aren't without use, however! They can be vibrant homes for beautiful aquatic plant life and algae, including trendy marimo moss balls (gorgeous, fluffy balls of vivid algae that can live for decades).
11–20 Gallons
Tanks that hold between 11–20 gallons are very affordable and adequate for fish owners looking for manageable tanks that won't take up too much space. Many fish tank sizes at the lower end of this range tend to be decorative and are used as home decor.
20-gallon tanks can comfortably house a handful of smaller fish. These tanks will still require vigilant maintenance to ensure the proper filtration and chemical balance. If you're a beginner looking for aquarium sizes to hold approximately a half dozen fish under 3" in length, a tank that holds 11–20 gallons might be right for you.
21–40 Gallons
Aquarium dimensions that range between 21–40 gallons are optimal for keeping approximately half a dozen to a dozen small fish healthy and happy. Their volume ensures that the water quality isn't overly temperamental and they are a bit more forgiving to less vigilant maintenance.
Larger tanks make great conversation pieces for your home space as well. Once you have your tank set up with its substrate (sand or gravel at the bottom of the tank) and environmental features, your aquatic world and its fish inhabitants will be the focal point of any space.
Over 40 Gallons
Aquariums that hold 40 gallons or more (some aquariums hold over 300 gallons!) are optimal for beautifully and comfortably displaying a diverse range of fish. Big fish tanks are stunning in appearance and make lovely homes for fish of many sizes.
Large fish tanks – especially tanks that breach 90 gallons in capacity – can benefit from a special aquarium stand or structural reinforcements to support their weight. Many of these big fish tanks come with their own built-in stands. Make sure that the dimensions and weight of the whole unit will fit in your space. These fish tanks are ideal for achieving your very own at-home aquarium, as they provide plenty of space for multiple species of fish, aquatic plants, rock formations, and corals.
Tip!
When shopping for aquarium dimensions, look at the "Weights & Dimensions" tab for a tank's exact L x W x H measurements as well as its weight when empty and its water capacity. Tanks of the same capacity aren't one-size-fits-all. They can vary in shape, so it's very important to look at the exact dimensions to ensure you have enough space before you buy. Keep in mind that you'll need a few inches above your aquarium for feeding purposes, maintenance, and accessories like tank hoods or lights.
Fish Tank Sizes & Corresponding Weights
One of the most important metrics to keep in mind when buying an aquarium or fish tank is its weight when filled appropriately with water and substrate (sand or gravel layer on the bottom of the tank). While an aquarium's dimensions may make it the appropriate size for a table or stand in your home, its filled weight may require more support. A single gallon of water weighs approximately 8.34 pounds, which means 180-gallon aquariums can weigh over a ton. Take a look at the chart above for a quick overview of how much water weight corresponds to each aquarium capacity.
Note that these weights represent only the weight of the aquarium's water when filled to the brim. They do not take into account the weight of the empty aquarium, which may vary depending on the material and included accessories. For example, acrylic aquariums weigh slightly less than glass aquariums of the same dimensions.
Additionally, these weights don't account for any substrate or environmental accessories you may add or the recommended inch of empty space that should be left at the top of a filled aquarium. As with most aquarium metrics, it's best to look at the specific weight and dimensions of the aquariums you want and calculate the filled weight on your own before you buy.
Tip!
Rather than perch your fish tank or aquarium on a table or cabinet that might not be able to hold its weight, consider shopping for an aquarium stand that is specially designed to hold your aquarium.
A rule of thumb for determining aquarium size is to use 1 gallon of water per inch of fish. This rule says that for each inch of fish you'd like to keep, your tank should be able to hold 1 gallon of water. It's important to note that this is just a general suggestion! Depending on the fish size/species, you might need to designate one fish to a tank that holds at least 5 gallons of water. You also need to take into account water surface area (essential for effective gas exchange), fish growth, waste production, body shape, activity levels, aggression, environmental needs (temperature, water salinity, etc.), and more. Be sure to do your research on your specific types of fish to make sure you are providing the proper environment for them.
Which Type of Fish Tank Should I Choose?
Before choosing a fish tank size, you'll need to decide which type of fish tank is best suited for your fish and your space.
- Aquarium/Tank: These transparent tanks are made of glass or acrylic and come in a wide range of sizes and shapes.
- Fish Bowl: With a small bowl-shaped silhouette, fish bowls are best suited for one or two small fish.
- Starter Kit: Starter kits include everything you'll need to start your own aquarium. These kits typically come with an aquarium tank and any essentials like gravel, a filtration system, or lighting.
When picking the right fish tank, it's important to consider if you'd prefer a saltwater or freshwater tank. This choice between saltwater and freshwater can impact the size and material of the tank as well as the type of fish that can live in it.
- Saltwater: Saltwater tanks require special filtration, so it's important to make sure the fish tank is large enough to accommodate a saltwater filter and that the filter can handle that volume of water. Common species of saltwater fish are clownfish, gobies, green chromis, or cardinalfish.
- Freshwater: Freshwater tanks are easy to clean and cost less to get started, which makes them great for first-time fish owners. Popular types of freshwater fish include bettas, goldfish, tetras, and cichlids.
- Saltwater & Freshwater: These types of fish tanks are suitable for either freshwater or saltwater fish and can be adapted to fit the needs of either species. This is a great third option if you aren't sure what type of fish you want to get or want a bit more flexibility for future use.
Material is another key consideration when browsing for a fish tank. The material can impact the durability and weight of the tank, so it's important to keep the material in mind.
Aquarium Materials
There are two main aquarium materials to choose from: glass and acrylic.
- Glass: Glass aquariums are affordable and easy to clean. They can be more fragile and come in less designs than acrylic aquariums, but are very scratch-resistant and maintain their clarity over years of use. If you choose a glass aquarium, it's important to place the aquarium on a flat surface large enough to accommodate the entire base to prevent any uneven weight distribution that could cause cracking.
- Acrylic: Acrylic aquariums are lighter than glass aquariums and come in plenty of designs. Though these aquariums are more prone to scratches, they are shatterproof and about 17 times more durable than glass. The increased durability and lightweight design make the higher price point a worthwhile investment.
Tip!
Shatterproof aquariums are typically made with high-definition glass or acrylic materials and guarantee the safety of your fish and their aquatic homes. Browse shatterproof fish tanks to ensure you choose the best option.
Aquarium Base Materials
Rather than placing an aquarium on a table, fish tanks can also be placed on a stand that is designed to support the weight of the aquarium. Aquarium bases also often feature cabinets below to store extra pet care or cleaning supplies.
- Metal: Metal aquarium bases are strong, reliable, and long-lasting. These durable bases are made from metals like steel or aluminum, and can be more expensive than wood bases.
- Wood: Wood aquarium bases are designed to resemble furniture and are less susceptible to warping than medium-density fiberboard (MDF). Wood bases are typically painted or sealed to avoid warping or water damage.
