Standard Aquarium Dimensions, Sizes & Weights

There are several ways to choose the ideal aquarium, but before settling on a particular tank, there are some basic calculations you’ll want to check. The advantage of going for standard aquarium sizes over a custom design is the ease of determining aquarium dimensions and weight, so let’s take a deeper look at these tanks!


If you have shopped for aquariums in recent years, you may have noticed that there are many options when it comes to modern tank styles and designs. This is a big change from the past when we only had the choice between standard size aquariums or shelling out big bucks for a custom tank.

These days, the main advantage of choosing a standard size aquarium over a single design is that you can easily search and compare its dimensions, capacities, and most importantly, estimate how much the full tank will weigh. This saves you from having to use an aquarium calculator or do the math by hand.


Standard aquariums are the classic rectangular glass tanks that are sealed with silicone and have a plastic base and rim for extra support. These tanks are made of glass that is typically 0.375 to 0.5 inches thick, with the larger 40+ gallon standards having additional support rails in the center of the aquarium.

Standard tanks measure externally through the plastic base. Measurements may vary slightly from one brand to another without altering its basic specifications. For example, all standard 10-gallon tanks are roughly the same dimensions (20 x 10 x 12 inches) and weigh about 111 pounds when filled with gravel and water.

It is very easy to compare standard tanks by looking at a table, like the ones we provide below. It’s harder to compare aquariums when you’re looking at a rimless arch front or other non-standard sizes like hexagonal fish tanks, and you’ll likely have to fiddle with those pesky calculators and make your own aquarium size charts.


Let’s compare specifications between a wide range of standard tank sizes, from small Nano aquariums to large behemoths weighing over a ton when full. Unlike the rest of the world, aquariums in the US are rated by their capacity in gallons of water rather than liters.


>Small aquariums range in capacity from 2.5 to 15 gallons of water, and many can easily fit on a sturdy desk or table, so you may not need to invest in an aquarium stand. While these sizes are popular with beginners, it is actually much more difficult to care for a small tank. Things can quickly go sideways in these little setups.

Standard Aquarium (US Gallons) Dimensions (L x W x H inches) empty aquarium weight Full freshwater weight
2.5 gallons 12x6x8 3 pounds 27 pounds
5 gallons 16x8x10 7 pounds 62 pounds
10 gallons “Leader” 20x10x12 11 pounds 111 pounds
15 gallons 24x12x12 21 pounds 170 pounds
15 gallons tall 20x10x18 22 pounds 170 pounds


The ideal capacity for a beginning fish breeder is a medium sized aquarium of 20 to 40 gallons. They are not very expensive to install, and with a robust filtration system and good aquarium maintenance, it is easy to avoid problems. However, if you look at their full weights, you can see that investing in a good stand is probably the way to go.

Standard Aquarium (US Gallons) Dimensions (L x W x H inches) empty aquarium weight Full freshwater weight
20 gallons tall 24x12x16 25 pounds 225 pounds
20 gallons long 30x12x12 25 pounds 225 pounds
25 gallons 24x12x20 32 pounds 282 pounds
29 gallons 30x12x18 40 pounds 330 pounds
30 gallon player 36x18x12 48 pounds 384 pounds
40 gallons long 48x12x16 55 pounds 455 pounds
40 gallon player 36x18x16 58 pounds 458 pounds


The largest standard aquariums range from 50 to almost 200 gallons in capacity, and these large aquariums require a lot of thought and planning. You’ll definitely want to invest in a quality bracket, perhaps with a matching hood, and you’ll probably need to measure the room to ensure you have room for equipment like filters, sinks or chillers.

Standard Aquarium (US Gallons) Dimensions (L x W x H inches) empty aquarium weight Full freshwater weight
50 gallons 36x18x19 100 pounds 600 pounds
55 gallons 48x13x21 78 pounds 628 pounds
65 gallons 36x18x24 126 pounds 772 pounds
75 gallons 48x18x21 140 pounds 850 pounds
90 gallons 48x18x24 160 pounds 1050 pounds
125 gallons 72x18x21 206 pounds 1400 pounds
150 gallons 72x18x28 338 pounds 1800 pounds
180 gallons 72x24x25 430 pounds 2100 pounds


Once you start considering tanks larger than 180 gallons, you really don’t have standard options to choose from. Each manufacturer has their own unique oversized models, often made from lighter materials like acrylic and with features like rounded corners and pre-drilled holes for coolers and sump filters. You’ll want to compare specific makes and models to find the best fit for your home.


There are several factors to consider before deciding on the size and style of a tank. Larger aquariums are easier to maintain and are a better choice for novice aquarists. If something goes wrong in a small capacity tank, it may not detect things in time to avoid a crash.


Obviously, you’ll want to choose a tank that physically fits the location you’ve chosen for your aquarium. The dimensions of your tank directly impact its weight, and you should not assume that tanks with the same capacity will have the same full weight, especially when comparing standard designs to non-standard designs.

For example, you’ll notice that the two standard 40-gallon tanks differ in empty and full weight by a few pounds, even with similar capacities. It is better to overestimate the fill weight of your aquarium rather than risk collapse. Most of the weight of your tank comes from the substrate/decoration and the water it contains.


Typically you will add about 1 pound of growing medium per gallon of water, but this varies quite a bit. For compact options like sand and fine gravel, you’ll often have to use half or twice as much to get the coverage you need, especially for planted tanks and those with aquatic spaces. A standard 10 gallon planted can easily weigh over 120 pounds.

How much does a gallon of water weigh?

The weight of a gallon of water varies a bit around the world as it depends on the density of the water and how it is measured. In the US, a gallon of water contains 3,785 litres, while the UK imperial gallon equals 4,546 litres. So you’ll want to double-check your units of measure to avoid making a mistake.

Fresh water is lighter than salt water, and the exact weight of a gallon of water depends on temperature, mineral content, and salinity.Fresh water weighs approximately 8,345 pounds per gallon and a gallon of salt water weighs approximately 8,554 pounds.

freshwater fish vs saltwater fish

You’ll also want to consider what type of fish you’d like to have and whether you prefer a freshwater or saltwater setup. The size and capacity of your aquarium will influence the types of animals you can keep and how many aquatic pets will fit nicely into your community.

Freshwater Fish Size Guide

Freshwater aquariums are the best type for beginners and beginners as they are easier to set up and maintain. While the general rule of thumb is to allow at least 1 gallon of water per inch of fish in a freshwater aquarium, it just depends on the needs of each species:

  • Neon Tetras are only 1.5 inches long, but they need at least a 10-gallon tank because they prefer to be kept in groups of 10 or more.
  • A group of three guppies, on the other hand, do well together in a 5-gallon tank.
Species Medium size (long) US gallons per fish Minimum tank size
Betta fish 2.5 to 5 inches 2.5 to 5 gallons 2.5 to 5 gallons
common goldfish 8 to 12 inches 20 to 30 gallons 20 gallons
fancy goldfish 6 to 8 inches 15 to 20 gallons 15 gallons
neon tetra 1.5 inches 1 to 2 gallons 10 gallons
guppies 1 to 2.5 inches 1 to 2 gallons 5 gallons

Saltwater Fish Size Guide

Salt water tanks require a higher investment in equipment such as chillers, wave generators and LED lights and are more complicated to install and maintain. It’s usually best to get some fishing experience before diving into a saltwater setup.

  • Saltwater fish require more care in general, as even refilling the water in the tank requires you to pay attention to the salinity levels of the water.
  • Depending on their size and activity levels, some saltwater fish need very spacious environments to stay healthy.
  • Saltwater fish are also more expensive to purchase, so stocking a tank can be an expensive undertaking.
Species Medium size (long) Minimum tank size
Clownfish 3 inches 30 gallons
yellow tang 8 inches 100 gallons
watchful goby 4 inches 30 gallons
azure damsel 2.5 inches 30 gallons
purple fire fish 2.5 to 3.25 inches 10 gallons


The best size and shape for your aquarium also depends on how you plan to use it. Non-standard designs like tall portrait and bucket tanks are attractive, but are often a poor choice for really active swimmers such as goldfish.

  • If you only need small tanks for a hospital or quarantine facility, a couple of standard 5 or 10 gallons may be ideal. They are compact but wide enough for fish to swim through and you can change gear between tanks when needed.
  • Breeding tanks are a popular choice for medium-sized community aquariums because their deep, shallow design allows for more surface area and better gas exchange.
  • Tall style tanks are a great way to show off a mixed community, and the extra height can help your middling dwellers and surface fish stand out.


Standard aquariums make it easy to design and set up your tank, as you can easily look up its dimensions and estimate its filled weight without having to rack your brain with equations. What size aquarium did you go for and did you choose a standard tank or a unique design? Share your comments below!

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