Aquarium Dimensions & Weight: Length, Width, & Height

Aquarium dimensions and sizes vary by brand and the type of aquarium. For instance, Aqueon might make its 20-gallon tank larger or smaller than Seapora‘s 20-gallon aquarium. It’s essential to know the dimensions of the tank as it lets you know which equipment is compatible with the aquarium. For example, when buying hoods, stands, covers, or lights for your aquarium.

By knowing the weight of your aquarium when it’s empty or full, you guess where you can put it and what type of stand can hold the weight. Things like decorations, plants, the thickness of the aquarium, and water quality all affect the weight. Saltwater weighs more than fresh water. So, the weights listed below are rough estimates to give you a bit of guidance.

Aquarium Dimensions Chart

aquarium size chart and aquarium weight chart
Aquarium Size Chart/ Aquarium Weight Chart

Things To Consider About Aquarium Sizes

Small tanks, as per aquarium dimensions, range from 2.5 gallons to 15-gallon aquariums. These tanks are suitable for a single small fish or five small fish if you get the 15-gallon tank.

small fish tank sizes and small fish tank weight
Small fish tank sizes and small fish tank weight

Small Tanks

Small aquariums need special care because they have a limited bio-load capacity. So, you need to set up proper filtration and not add too many fish or other animals to these tanks.

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Medium Tanks

Mid-size fish tank sizes range from 20 to 40 gallons. Mid-sized aquariums are available in several shapes and sizes and they can house both freshwater and saltwater fish. Some of these aquariums include a kit with lights, filtration, and aquarium decorations.

Medium fish tank sizes and medium fish tank weight - aquarium dimensions.
Medium fish tank sizes and medium fish tank weight

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Large Tanks

Large aquariums range from 50 gallons to 180 gallons. These tanks usually come in shapes like bow fronts and rectangles. Larger aquariums generally house coral and saltwater fish (marine animals).

Large fish tank sizes and Large fish tank weight

Breeder Tanks

Breeder tanks usually have unique dimensions. For instance, instead of being rectangular, a breeder tank can be hexagonal. You don’t need to buy specialty tanks, but be aware of the different shapes and dimensions so that it fits where you plan to put it. For example, a 40-gallon breeder tank and a 40-gallon long tank have different sizes and weights (see chart above).

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

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

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 lbs1206 lbs
150 gallon72″ x 18″ x 28″338 lbs1838 lbs
180 Gallon72″ x 24″ x 25″430 lbs1870 lbs
225 Gallon72″ x 27.5″ x 27.5″358 lbs2158 lbs
Chart: Aquarium Dimensions & Weight: Length, Width, & Height


You need to consider the space that you want to place your fish tank. Not only do you have to consider the dimensions and weight, but the whole setup. The setup includes lighting, filters, heaters, etc.

Other things to consider:

  • Space the stand or cabinet.
  • Space between the back of the aquarium and the wall.
  • Free space around the front, sides, and above the tank.

You don’t want to keep your aquarium in high-traffic areas where you accidentally break it. You also don’t want too much traffic and noise that might startle fish and other animals. Don’t hang items over the aquarium. Don’t place the aquarium under shelves.

You need space behind and around the aquarium. So, choose a size that allows you to attach things like a power filter or canister filter. You may need an air hose, digital timer, heater, etc. So, access to a power supply is essential. You also have to have enough space so that you can maneuver around the tank for cleaning and maintenance.


The kinds of fish, shrimp, snails, freshwater clams, plants, crayfish, etc. all impact the aquarium size. Some species of fish or crustaceans are territorial and aggressive. Aquarium crayfish are one such species. So, in this case, a larger aquarium would be best to give all the animals enough space.

Some fish like Oscar Cichlids are big and need larger sized tanks to accommodate their size. Freshwater shrimp and freshwater snails can survive in smaller aquariums so long as you avoid overstocking.