A Cheat Sheet to Fish Tank Gallon Sizes and Dimensions

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Fish Tank Measurements With Standard Shapes

Firstly I will be listing the dimensions and gallon capacities of the most popular aquariums with a standard rectangular shape.

After that, I will list the branded tanks with irregular shapes and sizes.

Here are the dimensions and gallon sizes of all standard fish tanks:

Small Standard Aquariums

You’d want to avoid getting a small tank if you’re a complete beginner in fish keeping.

Smaller tanks get polluted the quickest and it’s more difficult for a beginner to keep the water parameters in check.

Tank SizeDimensions in Inches
L x W x H
Aquarium Shape
2.5 Gallon12.25 x 6.25 x 8.125Standard Rectangular
5 Gallon16 x 8 x 10Standard Rectangular
5.5 Gallon16.25 x 8.375 x 10.5Standard Rectangular
10 Gallon Leader20.25 x 10.5 x 12.6Standard Rectangular
10 Gallon Long24.25 x 8.5 x 12.6Standard Rectangular
15 Gallon24.5 x 12.5 x 12.75Standard Rectangular
15 Gallon Tall20.25 x 10.5 x 18.75Standard Rectangular
15 Gallon Show24.25 x 8.5 x 16.6Standard Rectangular

Mid-Sized Standard Aquariums

If you’re a fish keeping beginner you’d want to start with a mid-sized tank as it’d be easier to manage.

I realize we all may have space and budget constraints but if you have the means to – go for a middle-sized aquarium.

Tank SizeDimensions in Inches
L x W x H
Aquarium Shape
20 Gallon Tall24.25 x 12.5 x 16.75Standard Rectangular
20 Gallon Long30.25 x 12.5 x 12.75Standard Rectangular
20 Gallon Extra Tall20.25 x 10.5 x 23.75Standard Rectangular
23 Gallon Long36.25 x 12.625 x 13Standard Rectangular
25 Gallon24.25 x 12.5 x 20.75Standard Rectangular
29 Gallon30.25 x 12.5 x 18.75Standard Rectangular
30 Gallon36.25 x 12.625 x 16.75Standard Rectangular
30 Gallon Breeder36.25 x 18.25 x 13Standard Rectangular
30 Gallon Extra Tall24.25 x 12.5 x 24.75Standard Rectangular
33 Gallon Long48.25 x 12.75 x 13.375Standard Rectangular
37 Gallon30.25 x 12.5 x 22.75Standard Rectangular
38 Gallon36.25 x 12.625 x 19.75Standard Rectangular
40 Gallon Breeder36.25 x 18.25 x 17Standard Rectangular
40 Gallon Long48.25 x 12.75 x 16.875Standard Rectangular
45 Gallon36.5 x 12.625 x 23.75Standard Rectangular
45 Gallon Long48.25 x 12.75 x 19Standard Rectangular

Large Standard Aquariums

Large tanks can be very rewarding if you do your homework.

Nothing compares to having a big ecosystem with lots of small schooling fish, turtles or monster fish at home.

Larger aquariums are also the most stable in terms of water parameters.

Tank SizeDimensions in Inches
L x W x H
Aquarium Shape
50 Gallon36.375 x 18.375 x 19Standard Rectangular
55 Gallon48.25 x 12.75 x 21Standard Rectangular
60 Gallon48.375 x 12.875 x 23.875Standard Rectangular
65 Gallon36.375 x 18.375 x 25Standard Rectangular
75 Gallon48.5 x 18.5 x 21.25Standard Rectangular
80 Gallon Extra Tall48.875 x 14 x 30.75Standard Rectangular
90 Gallon48.5 x 18.5 x 24.375Standard Rectangular
100 Gallon72.5 x 18.5 x 19.375Standard Rectangular
110 Gallon Extra Tall48.875 x 19 x 30.75Standard Rectangular
120 Gallon48.5 x 24.5 x 25.5Standard Rectangular
125 Gallon72.5 x 18.5 x 21Standard Rectangular
150 Gallon72.5 x 18.5 x 29.5Standard Rectangular
180 Gallon72.5 x 24.5 x 25.625Standard Rectangular
210 Gallon72.5 x 24.5 x 29.625Standard Rectangular
225 Gallon72.5 x 27.5 x 27.5Standard Rectangular

Measurements of Brand Fish Tanks With Irregular Shapes and Sizes

Branded tanks don’t follow any rules about dimensions or gallon capacities.

They are mostly unique and the brand that makes the tank decides what its measurements would be.

Here are the dimensions of all irregularly-shaped aquarium kits:

Small Branded Aquariums

Starting with the dimensions of the smallest branded tanks, this is probably the longest chart in this list.

That’s because many brands recognize that small tanks are the biggest revenue drivers (which is not a good thing, since as I said earlier, beginners should ideally start with a mid-sized tank).

Aquarium KitDimensions in Inches L x W x HShape
0.5 Gallon Penn Plax Aqua-ponic5.875 x 5.875 x 8Cylinder
1 Gallon Aqueon Frameless6.375 x 6.375 x 6.375Cube
1 Gallon Koller Kit7.5 x 10.5 x 10.2Pentagon
1 Gallon Koller Hex7.8 x 7.8 x 8Hexagon
1 Gallon Koller BettaTank9 x 9 x 10Bowl
1 Gallon Koller Deco15 x 3.8 x 8.5Half Circle
1 Gallon Aqueon MiniBow LED Kit8.5 x 6.25 x 9.25Bow Front
1.4 Gallon Penn Plax Aqua-ponic7.875 x 7.875 x 10Cylinder
1.5 Gallon Tetra LED Cube Kit8.00 x 8.20 x 10.20Cube
1.5 Gallon Tetra GloFish Kit7.25 x 8.5 x 11.5Cube
1.5 Gallon Koller AquaScene8.5 x 8.5 x 9Cube
1.5 Gallon Koller BettaView 3608.1 x 8.1 x 9.8Cylinder
1.5 Gallon Koller AquaView9 x 8.2 x 10.8Half Cylinder
1.5 Gallon Penn Plax Betta Fish Kit8.5 x 6 x 9.5Rectangular
1.6 Gallon Koller BettaTank Pedestal9.5 x 9.5 x 9.5Bowl
1.7 Gallon Koller BettaTank9.5 x 9.5 x 11Bowl
1.7 Gallon Koller AquaScene8.4 x 8.4 x 11Hexagon
1.8 Gallon Tetra Waterfall Globe12 x 10.75 x 13.5Bowl
2 Gallon Fluval Spec7.25 x 9.25 x 10Rectangular
2 Gallon Koller Hex9.2 x 9.2 x 9.2Hexagon
2 Gallon Koller AquaView 36010.2 x 10.2 x 10.5Cylinder
2 Gallon Koller Gumball8.5 x 8.5 x 10Bowl
2 Gallon Penn Plax Prism Nano7 x 10 x 9Rectangular
2.5 Gallon Koller AquaView9.5 x 9.5 x 11.2Pentagon
2.5 Gallon Koller AquaTunes9.5 x 9.5 x 11.2Pentagon
2.5 Gallon Koller AquaTunes9.5 x 9.5 x 11.2Cube
2.5 Gallon Aqueon BettaBow LED Kit11.5 x 7.63 x 12.5Bow Front
2.5 Gallon Aqueon MiniBow LED Kit11.5 x 7.63 x 12.5Bow Front
2.6 Gallon Fluval Spec10.8 x 11.8 x 8.7Rectangular
2.65 Gallon Marina 36010 x 10 x 10Cylinder
2.7 Gallon Penn Plax Vertex10 x 9 x 7.75Cube
3 Gallon Tetra LED Cube Kit10.3 x 11 x 17.5Cube
3 Gallon Marineland Silhouette14.2 x 13.7 x 12.3Rectangular
3 Gallon Tetra GloFish Kit14.6 x 8.8 x 11.2Rectangular
3 Gallon Tetra ColorFusion Half Moon12.9 x 6.8 x 12.5Half Cylinder
3 Gallon Marineland Contour Desktop9.63 x 9.63 x 14Cube
3 Gallon Tetra Bubbling Half Moon12.9 x 6.8 x 12.5Half Cylinder
3 Gallon Tetra GloFish Half Moon7.5 x 7.5 x 7.7Half Cylinder
3 Gallon Tetra GloFish Crescent13 x 7 x 9.5Bow Front
3 Gallon Aqueon Frameless9.25 x 9.25 x 9.25Cube
3 Gallon Koller AquaView 36010.2 x 10.2 x 14.5Cylinder
3 Gallon Koller AquaView14.5 x 10 x 9.2Flat Back Hexagon
3 Gallon Koller AquaTunes12.8 x 11.8 x 9Cylinder
3 Gallon Koller AquaView11.5 x 11 x 11Bowl
3 Gallon Marineland Nook Kit13 x 7.1 x 9.3Bow Front
3.4 Gallon Penn Plax Water World10.25 x 7.75 x 11Rectangular
3.5 Gallon Koller AquaView11.2 x 8.8 x 13.5Half Cylinder
3.5 Gallon Koller AquaTunes11.2 x 8.8 x 13.5Half Cylinder
3.5 Gallon Koller11.2 x 8.8 x 13.5Half Cylinder
4 Gallon biOrb Classic11.75 x 11.75 x 12.5Bowl
4 Gallon biOrb Flow8.19 x 11.81 x 12.4Rectangular
4 Gallon biOrb Halo11.81 x 11.81 x 13Bowl
4 Gallon biOrb Life11.41 x 7.6 x 16Rectangular
4 Gallon biOrb Tube12.91 x 12.91 x 12.4Cylinder
4.5 Gallon Koller AquaView14.8 x 10.8 x 13.2Double Bullnose
5 Gallon Marineland Portrait11.8 x 11.6 x 17Cube
5 Gallon Marineland Contour Desktop9.6 x 9.6 x 19Cube
5 Gallon Tetra Crescent16.5 x 11.25 x 13.2Bow Front
5 Gallon Tetra ColorFusion Bubbling16 x 8 x 10Rectangular
5 Gallon Tetra GloFish Glass16 x 8 x 10Rectangular
5 Gallon Tetra GloFish Crescent15.5 x 9 x 11.5Bow Front
5 Gallon Fluval Chi10 x 10 x 14.4Rectangular
5 Gallon Fluval Spec20.5 x 11.6 x 7.5Rectangular
5 Gallon Fluval EVO20.5 x 11.6 x 7.5Rectangular
5 Gallon Marina Kit18.5 x 10.8 x 13.3Rectangular
5 Gallon Koller PanaView14.2 x 11.5 x 10Round-edge Rectangular
5 Gallon Aqueon MiniBow LED Kit14.5 x 10 x 13.5Bow Front
5 Gallon Aqueon NeoGlow11.438 x 11.31 x 14.813Cube
5 Gallon Marineland Nook Kit15.2 x 5 x 11.25Bow Front
5 Gallon Marineland Escape 514 x 12.5 x 13.5Hexagon
5 Gallon Penn Plax Water World13.75 x 8.75 x 11Rectangular
5 Gallon Penn Plax Vertex12 x 10.5 x 9.75Cube
5.5 Gallon Aqueon NeoGlow16.5 x 8.75 x 10.5Rectangular
6 Gallon Aqueon Frameless11.5 x 11.5 x 11.5Cube
6 Gallon Koller AquaView 36011 x 11 x 19.8Cylinder
6 Gallon Aqueon Ascent Frameless16 x 8.125 x 13.5Rectangular
6 Gallon Fluval Edge16.9 x 10.25 x 14Rectangular
6.5 Gallon Koller18 x 11 x 13.5Flat Back Hexagon
7 Gallon Koller AquaView18.25 x 12.38 x 13.10Bow Front
7.5 Gallon Aqueon NeoGlow14.813 x 14 x 13.813Cube
7.5 Gallon Aqueon Shrimp Kit13 x 12 x 14Cube
8 Gallon Aqueon NeoGlow15 x 13 x 15.25Hexagon
8 Gallon biOrb Classic15.75 x 15.75 x 16.5Bowl
8 Gallon biOrb Cube12.6 x 12.6 x 13.6Cube
8 Gallon biOrb Flow10.23 x 14.96 x 15.35Rectangular
8 Gallon biOrb Halo15.75 x 15.75 x 18.11Bowl
8 Gallon biOrb Life15.75 x 9.25 x 16.54Rectangular
8 Gallon biOrb Tube12.91 x 12.91 x 20.2Cylinder
8.75 Gallon Aqueon Shrimp Kit18.25 x 12 x 13Rectangular
8.8 Gallon Aqueon Aqua Springs15 x 15 x 14.75Cube
9 Gallon Fluval Flex14 x 13 x 13Vertical Bow Front
9 Gallon biOrb Tube16.14 x 16.14 x 14.53Cylinder
10 Gallon Marineland BIO Wheel20 x 10 x 12Rectangular
10 Gallon Tetra ColorFusion Bubbling20 x 10 x 12Rectangular
10 Gallon Tetra PLAYMOBIL20 x 10 x 13Rectangular
10 Gallon Tetra Complete LED20 x 10 x 12Rectangular
10 Gallon Tetra Goldfish20 x 10 x 12Rectangular
10 Gallon Tetra Half Moon17.75 x 11 x 17Half Cylinder
10 Gallon Tetra GloFish Glass20 x 10 x 12Rectangular
10 Gallon Aqueon Glass14.5 x 12.625 x 18.375Hexagon
10 Gallon Marina Kit22.6 x 12.6 x 15.3Rectangular
10 Gallon NUVO Fusion Pro11.8 x 15 x 13Cube
10 Gallon Aqueon20.25 x 10.5 x 15Rectangular
10 Gallon Aqueon Ascent Frameless18.75 x 10 x 15.75Rectangular
10 Gallon Aqueon Hexagon LED Kit14.5 x 13.375 x 14.75Hexagon
10 Gallon Aqueon Incandescent LED Kit22.88 x 12.75 x 13.88Rectangular
10 Gallon Aqueon NeoGlow20.5 x 10.5 x 12.5Rectangular
10 Gallon Penn Plax Water World17.75 x 11.75 x 12.63Rectangular
10 Gallon Penn Plax Vertex13.75 x 13.75 x 13.75Cube
11 Gallon Aqueon Framless20.25 x 10.5 x 12.625Rectangular
11 Gallon Aqueon Frameless20.25 x 10.5 x 12.625Rectangular
11 Gallon Aqueon Aqua Springs15 x 15 x 17.75Cube
12 Gallon Fluval Edge17.5 x 10.25 x 22.9Cube
12 Gallon biOrb Life14.76 x 10 x 22.04Rectangular
13.5 Gallon Fluval EVO22 x 15 x 11.5Rectangular
14 Gallon Aqueon Frameless15.125 x 15.125 x 15.125Cube
14 Gallon NUVO Fusion Pro Peninsula11.8 x 20 x 13Rectangular
14.5 Gallon Fluval Flora15 x 15 x15Cube
15 Gallon Fuval Flex16 x 15 x 15Vertical Bow Front
15 Gallon SeaClear Deluxe15 x 15 x 20Hexagon
15 Gallon Aqueon Column13.75 x 13.75 x 25Cube
16 Gallon Aqueon20.25 x 12.875 x 17.75Bow Front
16 Gallon Fluval Spec21.8 x 11.5 x 17.5Rectangular
16 Gallon Aqueon Bow Front LED Kit20.25 x 12.875 x 20.5Bow Front
16 Gallon biOrb Classic19.75 x 19.75 x 20.5Bowl
16 Gallon biOrb Cube15.75 x 15.75 x 17Cube
16 Gallon biOrb Halo19.66 x 19.66 x 22.83Bowl
16 Gallon biOrb Life16.54 x 11 x 24.4Rectangular

Mid-Sized Branded Aquariums

The mid-sized branded tanks can also be good for starters in the hobby, as long as they are not too weirdly-shaped.

Aquarium KitDimensions in Inches L x W x HShape
20 Gallon Marineland BIO Wheel24 x 12 x 16Rectangular
20 Gallon Tetra Complete LED24 x 12 x 16Rectangular
20 Gallon Tetra Goldfish24 x 12 x 16Rectangular
20 Gallon Aqueon Glass18.75 x 16.25 x 20.625Hexagon
20 Gallon SeaClear Deluxe15 x 15 x 24Hexagon
20 Gallon SeaClear24 x 13 x 16Rectangular
20 Gallon Marina Kit26.3 x 15 x 19Rectangular
20 Gallon NUVO Fusion Pro23.62 x 15 x 13Rectangular
20 Gallon NUVO Fusion Pro Peninsula11.8 x 30 x 13Rectangular
20 Gallon NUVO Concept Pro Peninsula15 x 20 x 13Drop Off Rectangular
20 Gallon NUVO Concept Pro20 x 15 x 13Drop Off Rectangular
20 Gallon Aqueon Ascent Frameless23.75 x 12.625 x 19.75Rectangular
20 Gallon Aqueon Hexagon LED Kit18.75 x 16.25 x 23Hexagon
20 Gallon Marineland Half Moon Combo23.5 x 12.12 x 23.45Half Cylinder
21 Gallon Aqueon Framless24.25 x 12.25 x 16.75Rectangular
21 Gallon Aqueon Frameless24.25 x 12.25 x 16.75Rectangular
25 Gallon NUVO Fusion Pro Lagoon23.62 x 19.68 x 11.8Rectangular
25 Gallon NUVO EXT Lagoon23.6 x 19.7 x 11.8Cube
26 Gallon Aqueon24.125 x 14.75 x 20.875Bow Front
26 Gallon SeaClear36 x 12 x 16Flat Back Hexagon
26 Gallon Aqueon Bow Front LED Kit24.125 x 14.75 x 23.625Bow Front
28 Gallon Tetra Connect24 x 15 x 18.9Bow Front
28 Gallon biOrb Classic24 x 24 x 25Bowl
29 Gallon Marineland BIO Wheel30.25 x 12.5 x 18.75Rectangular
29 Gallon Tetra Complete LED30 x 12 x 18Rectangular
29 Gallon SeaClear30 x 12 x 18Rectangular
30 Gallon Aqueon Framless30.25 x 12.5 x 18.75Rectangular
30 Gallon SeaClear36 x 12 x 16Rectangular
30 Gallon NUVO Fusion Pro35.43 x 14.96 x 12.99Rectangular
30 Gallon NUVO EXT35.4 x 15 x 13Rectangular
30 Gallon Aqueon Frameless30.25 x 12.5 x 18.75Rectangular
30 Gallon Marineland Half Moon Combo26.7 x 13.5 x 26.9Half Cylinder
32.5 Gallon Fluval Flex32.5 x 15.35 x 15.75Vertical Bow Front
35 Gallon Aqueon Glass23.25 x 20.25 x 24.75Hexagon
35 Gallon Aqueon Hexagon LED Kit23.25 x 20.25 x 27.125Hexagon
36 Gallon Aqueon30.25 x 15.5 x 20.875Bow Front
36 Gallon Aqueon Bow Front LED Kit30.25 x 15.5 x 23.625Bow Front
40 Gallon SeaClear36 x 12 x 16Rectangular
40 Gallon NUVO Fusion Pro23.62 x 19.68 x 18.89Cube
45 Gallon NUVO EXT23.6 x 19.7 x 18.9Cube
46 Gallon Aqueon36.375 x 16.375 x 20.875Bow Front
46 Gallon SeaClear36 x 16.25 x 20Bow Front

Large Branded Aquariums

And finally, here are the dimensions of large branded tanks that have irregular shapes.

Aquarium KitDimensions in Inches L x W x HShape
50 Gallon SeaClear36 x 15 x 20Rectangular
50 Gallon NUVO Fusion Pro Lagoon29.92 x 23.62 x 16.14Rectangular
50 Gallon NUVO EXT Lagoon30 x 23.6 x 16.1Rectangular
50 Gallon NUVO INT23.6 x 23.6 x 19.7Cube
54 Gallon Aqueon39 x 27.25 x 23Corner Bow Front
55 Gallon Marineland BIO Wheel48.25 x 12.75 x 21Rectangular
55 Gallon Tetra Complete LED48 x 13 x 21Rectangular
60 Gallon NUVO SR Pro35.43 x 23.62 x 16.14Rectangular
70 Gallon NUVO INT23.6 x 35.4 x 55Drop Off Rectangular
72 Gallon Aqueon48.375 x 18 x 23Bow Front
75 Gallon NUVO EXT35.4 x 23.6 x 19.7Rectangular
75 Gallon NUVO INT35.4 x 23.6 x 19.7Rectangular
90 Gallon NUVO SR Pro47.24 x 23.62 x 16.14Rectangular
100 Gallon NUVO EXT47.3 x 23.6 x 19.7Rectangular
100 Gallon NUVO INT47.3 x 23.6 x 19.7Rectangular
112 Gallon NUVO INT Lagoon35.4 x 35.4 x 19.7Cube
150 Gallon NUVO INT Lagoon47.3 x 35.4 x 19.7Rectangular
200 Gallon NUVO INT70.9 x 30 x 21.7Rectangular
200 Gallon NUVO EXT70.9 x 30 x 21.7Rectangular

How to Calculate the Weight of Your Aquarium?

To calculate the total weight of an aquarium you’d want to first figure out how much it weighs empty.

After that, you calculate the water weight and then add the two together. To find out how much your tank weighs follow these steps:

  1. Calculate the surface area of the fish tank.

    To find the total surface area of your tank you’d need to find the surface areas of each of its walls, including the bottom, and add them together.

    The surface area of each rectangular flat surface is calculated by multiplying its sides.

    So if your tank’s wall measures 10 x 20 inches, then you multiply that and get that the surface area of that wall is 200 square inches.

    Do this for each of the tank’s flat surfaces and add them together.

    The formula for finding the surface area for a standard rectangular tank is:

    (2 × length × height) for the sides + (2 × width × height) for the other two sides + (width × length) for the bottom.

    Bowfront tanks are an exception to this formula because they have a curved wall which is almost impossible to calculate on your own at home.

  2. Calculate the empty weight of your tank.

    To calculate the empty weight of a tank you’d want to multiply its total surface area by the thickness of the walls.

    The material your tank is made of plays a role here since different materials have different weights.

    Typically aquariums are made of acrylic or glass. Glass weighs roughly 0.5165 pounds per square foot for each millimeter of thickness.

    Acrylic weighs approximately 0.24 pounds per square foot for each millimeter of thickness.

    Measure the thickness of the tank’s walls in millimeters and write that down.

    To proceed with calculating the tank’s empty weight you’d want to convert the square inches of total surface area we found in step 1 into square feet.

    This is easily done by dividing the total square inches by 144 since there are 144 sq inches in an sq foot.

    After you convert the surface area of the fish tank in square feet multiply that by the thickness of the glass in millimeters and the specific weight of the material.

    The formula looks like this:

    Tank Surface Area in Square Feet × Thickness of the Wall in mm × Specific Material Weight.

    For example, if your tank has 7 square feet of surface area, with a wall thickness of 10 mm, and is made of glass the calculation would be 7 × 10 × 0.5165 = 36.155 pounds of empty weight.

  3. Calculate the gallon capacity of the tank.

    All tanks that you buy from the store will have a label clearly stating how much water they can hold.

    However, if you get a second-hand tank or have just forgotten what it was there is a way to calculate that.

    You simply need to convert the tank’s height, length, and width from inches to feet, then multiply them to find out the volume in inches.

    Turn that into cubic feet and multiply the result by 7.48. To convert the cubic inches into cubic feet you need to divide the volume by 1728.

    If this seems counterintuitive thank the Imperial unit system.

    Taking this into account you can use the following formula to calculate the gallon capacity of your tank:

    (Lenght × Width × Height, all in inches) ÷ 1728 x 7.48

    So if you have a tank that measures 10 × 20 × 15 inches and you’re going to fill it with fresh water, then the calculation would look like this:

    ((10 × 20 × 15) ÷ 1728) × 7.48 = roughly 13 gallons.

  4. Calculate the filled weight of the tank.

    To do so you’d want to first find the weight of water and then add that up to the empty tank weight.

    To calculate the weight of water:

    Multiply the gallon capacity of your tank, which we found in step 3 by how much water weighs per pound.

    Freshwater and saltwater have different weights because of their different density.

    Freshwater weighs 8.345 pounds per gallon. Saltwater is heavier and weighs about 8.554 pounds per gallon.

    So if your tank can hold 20 gallons and you want to fill it with freshwater then multiply 20 × 8.345 = 166.9 pounds.

    Now add that up to the tank’s empty weight (calculated in step 2) and you’d find the total weight of your tank when it’s filled to the brim with water.

I provided all the formulas so that anyone with a non-standard tank can figure it out on their own.

For a generic weight estimate of standard tanks you can use a fish tank weight calculator like this one.

Getting equipment according to the dimensions of the aquarium?

Selecting aquarium equipment based on the size of the tank is essential for its long-term success.


aquarium lighting

The dimensions of a fish tank play a huge role in the choice of aquarium lighting because light itself has a limited water penetration.

If you’re in the middle of your research on choosing a suitable light fixture for your aquarium plants you can check my guide on that here.

In that link, I do specific product recommendations based on aquarium depth and the type of plants you may want to keep.

The same rules apply for picking adequate grow lights for saltwater reef aquariums.

Corals are very sensitive to the intensity and spectrum of the incoming light they use for photosynthesis.

To end up with the right LED light you’ll need to take into account the dimensions of your coral reef aquarium.

There are stronger units that penetrate the water well and are suitable for deeper reef tanks and others that are less intense, making a good addition to aquariums with less demanding corals.

I made specific recommendations on choosing the best LED lights for corals based on aquarium height and the species you want to keep. Visit the link to learn more.


Choosing the flow rate of a water filter should also be made in conjunction with the gallon capacity of the fish tank.

If you keep larger carnivorous fish that produce more waste or you plan to overstock the tank you’d want a stronger filter that turns the water at least 6 times per hour.

For Oscar or Cichlid fish tanks getting an external canister filter makes perfect sense as these units produce more flow and have enormous space for media, which in turn keeps the aquarium clean and safe.

I have an article on choosing one according to your aquarium’s gallon capacity (visit the link to learn how to make a choice).

If you want to keep aquatic turtles you should still take into consideration the available water volume in the aquarium.

In this case, you can check my article on picking a good filter for a turtle aquarium according to gallon capacity.

turtle tank

Turtles are messier than most aquatic pets and require a water turn over of at least 8 times the whole aquarium’s gallon capacity per hour.


A small 3-gallon, 5-gallon, or 10-gallon tank with tropical fish requires a small-sized aquarium heater that’s ideally under 6.5 inches in length.

I’ve seen enough small aquariums with a spoiled interior because the owner got an over-sized heater.


Last but not least, the gallon capacity of your reef tank, for example, plays a major role in your choice of aquarium wavemaker.

You can check my guide on how to make the correct choice by clicking here.

Knowing the exact dimensions of your new fish tank will give you the needed information to make adequate decisions on choosing livestock and the purchase of equipment.

Drop me a comment below if you have any questions in those areas and I will answer as soon as I see it.

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Momchil Boyanov is the Founder and now Senior Editor of AquAnswers. He has over 13+ years of experience in keeping home aquariums as well as providing professional aquarium services. Momchil has had his fair share of adventures in aquarium care. He has made MANY mistakes throughout his fishkeeping journey and thus learned A LOT. Through Aquanswers, Momchil shares knowledge about freshwater and saltwater aquariums with the people within this community.

19 thoughts on “A Cheat Sheet to Fish Tank Gallon Sizes and Dimensions”

  1. Fish aquarium dimension in feet 9*6*2(L*W*H) in ceiling how much water in use & How many fish stay there &Which types of fish pls halp for cafe

    • Hey, If I am understanding the question correctly this is a pretty sizeable tank. To calculate the volume of water used in the aquarium, we’ll multiply the length (L), width (W), and height (H) dimensions together. Given the dimensions are in feet, we’ll need to convert them to inches to get the volume in cubic inches, and then convert that to gallons.

      First, let’s calculate the volume:

      Length (L) = 9 feet = 9 * 12 inches = 108 inches
      Width (W) = 6 feet = 6 * 12 inches = 72 inches
      Height (H) = 2 feet = 2 * 12 inches = 24 inches

      Volume = Length (L) * Width (W) * Height (H)
      Volume = 108 inches * 72 inches * 24 inches
      Volume = 186,624 cubic inches

      Now, let’s convert the volume to gallons. Since 1 gallon is approximately equal to 231 cubic inches:

      Volume (in gallons) = Volume (in cubic inches) / 231
      Volume (in gallons) = 186,624 cubic inches / 231
      Volume (in gallons) ≈ 808.43 gallons

      So, approximately 808.43 gallons of water will be used in the aquarium.

      As for the number of fish that can stay in the aquarium, it depends on various factors such as the species of fish, their size, compatibility, filtration system, and maintenance routine. Please checkout some of our articles on large fish species. I hope this helps.

  2. Buenas tardes quiero construir un estanque de 300 cm x 60 xm ancho y 60 de alto.- Mi consulta principal es como hacerlo lo mas seguro posible.- desde ya muchas
    La idea es armarlo con peces tropicales y una buena vegetacion

  3. Great article! Wondering if you could help me with finding a gallon size of a 36” L x 12”D x 16”H flat back hexagon? Maybe a lid for it too

  4. Where can I get a 30 Gallon Extra Tall?

    • Good question.

      They are not very common so your best chance would be online.

  5. I have been looking high and low for a air pump that will be sufficient for my needs but is quiet and doesn’t get hot. Would like to know if the Fluval Q2 is a good choice and if it will be strong enough to run several 18″ air bars in the bottom of my soon to be standard size 120 gallon. I will be upgrading and I haven’t even be able to find one strong enough for my 55 gallon. Any help would be great.

  6. Have a 10inches in height 10inches in width and 12inches dept dont know what gallon it is? Help

    • Hi, that would be a 5-gallon tank.

      The formula is as follows:

      10 inches = 0.83 Feet
      12 inches = 1 Foot

      (Lenght x Width x Depth) in feet = 0.6889 Cubic Feet.
      Cubic ft x 7.47 = 5.15 Gallons.

  7. I have an aquarium that is 48″x 12″ x 31″ which is about 75 gallons. I am just wondering if you might know who it is made by? I can’t find any information about a tank with these dimensions.
    Thank you.

  8. My tank is a 30×12×12 is that consider a 20 gallon

    • In my calculations, that’s a little over 18 gallons.

  9. I don’t have the slightest idea of where to begin with this tank! This is all new to me. From your cheat sheet I am guessing I have a 29 gallon tank. I’m confused though as to which 29 gallon tank I have because you have different types of tanks listed. The tank was given to me. Once I figure this part out then maybe I can figure out where to go from there lol. Help please!

    • Hi Denise,

      Could you measure its dimensions? This will help in figuring out which one you have.

      From there on, you just need to equip it with the right filter / lighting according to the tank’s size and the setup you’d want to achieve (e.g. heavily planted, non-planted, lots of fish, etc.).


  10. Great information! Thank you for the article.

    • Thank you TKP!

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