Standard Aquarium Sizes and Weights

Get the Specs on Your Fish Tank

Young girl looking in fish tank
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Do you have a used aquarium that you don't have size information for? Or perhaps you want to know how much your tank will weigh once it's filled with water? No matter your goal, our charts for basic aquarium sizes will answer your questions. We'll also pass on a few tips for determining whether a small, medium, or large tank is best for you.

Basic Aquarium Sizes

Aquariums come in a large range of sizes, from as small as 2 1/2 gallons to as large as 180 gallons or more.

That's a dynamic range, so finding the right one for you is going to depend on what you want to do and your level of experience.

In the charts below, you will find the most common aquarium sizes. Each includes the size and weight information in U.S. units as well as the weight when it's filled with water. This is an important consideration, especially for larger tanks. Keep in mind that one gallon of water weighs 8.34 pounds, so you need to ensure that your cabinet and floor can handle that kind of weight.

With the help of these dimensions, you can plan the rest of your aquarium. The information will guide you in how much substrate and the size of lighting you will need, recommended filter sizes, and other equipment needs to get you started. Also, keep in mind that the surface area of the water in the tank will determine how many fish you can stock.

The weights given are for glass aquariums and acrylic aquariums will weigh less.

Also, exact dimensions can vary by brand and the trim used on the aquarium. It's sound advice to take a tape measure with you to the fish store to get exact measurements and ensure all your accessories—particularly tank hoods and cabinets—fit properly.

Small Aquariums

Contrary to what you might think, small aquariums are not recommended for beginners.

These small environments are very temperamental, so a tiny change in the water—ammonia, pH, etc.—can have a big impact.

If you do decide to keep a small fish tank, keep in mind that it will have a much smaller bio-load, so it's important that you do not overstock it. Also, because it is such a sensitive environment, good filtration is absolutely essential.

Tank SizeL x W x HEmpty WeightFilled Weight
2 1/2 gallon12" x 6" x 8"3 lbs27 lbs
5 gallon16" x 8" x 10"7 lbs62 lbs
10 gallon "Leader"20" x 10" x 12"11 lbs111 lbs
15 gallon24" x 12" x 12"21 lbs170 lbs
15 gallon High20" x 10" x 18"22 lbs170 lbs

Mid-Sized Aquariums

These are the aquariums that are most often recommended for beginners. Anything in the 20 to 40 gallon range will reduce any harmful effects of changes in the water and can take a nice stock of fish. 

Also, these are not so large that cleaning is a big hassle. This is important because many people who are new to aquariums find that keeping up with maintenance gets overwhelming after awhile. Overall, the mid-sized tanks are a nice, manageable size.

Tank SizeL x W x HEmpty WeightFilled Weight
20 gallon High24" x 12" x 16"25 lbs225 lbs
20 gallon Long30" x 12" x 12"25 lbs225 lbs
25 gallon24" x 12" x 20"32 lbs282 lbs
29 gallon30" x 12" x 18"40 lbs330 lbs
30 gallon Breeder36" x 18" x 12"48 lbs348 lbs
40 gallon Breeder36" x 18" x 16"58 lbs458 lbs
40 gallon Long48" x 12" x 16"55 lbs455 lbs

Large Aquariums

The larger the aquarium, the more fish you can stock. That's great, but it also means that you'll have to work harder to maintain these tanks. Tanks of this size also come with concerns over weight when they're filled, so make sure your floor and cabinet can handle such heavy loads.

Bigger tanks have a great appeal, especially when you want to create a diverse aquarium. However, you also need to consider the tank's scale in relation to the room and its surroundings.

Is there enough room for hoses and accessories between the tank and wall? Is it a high-traffic room? Are there space constraints that might lead to accidents and broken glass? Do you have shelves overhanging the tank that may fall down and create an emergency for your fish? These are important questions to ask before making such a significant investment with your time and money.

Tank SizeL x W x HEmpty WeightFilled Weight
50 gallon36" x 18" x 19"100 lbs600 lbs
55 gallon48" x 13" x 21"78 lbs625 lbs
65 gallon36" x 18" x 24"126 lbs772 lbs
75 gallon48" x 18" x 21"140 lbs850 lbs
90 gallon48" x 18" x 24"160 lbs1050 lbs
125 gallon72" x 18" x 21"206 lbs1400 lbs
150 gallon72" x 18" x 28"338 lbs1800 lbs
180 Gallon72" x 24" x 25"338 lbs2100 lbs