When I was in my teens and early into my aquarium journey I realized how much aquariums weigh through a near catastrophe!I had purchased a small 25 gallon aquarium as an upgrade for my Tropical Fish and sat it on top of my drawer unit, just like the smaller aquarium before it. No problems, right!?

Filled saltwater aquariums weigh 8.56 lb. / 3.88 kg per gallon and 2.26 lb. / 1.03 kg per liter. Filled freshwater aquariums weigh 8.34 lb. / 3.78 kg per gallon and 2.20 lb. / 1.00 kg per liter.The empty weight of the aquarium, stand, canopy, substrate, and rock is in addition to the water weight.

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My little 25 gallon freshwater aquarium weighed in at close to 200lb. and my cheap set of drawers were not happy! From that point on, every aquarium I owned had the manufacturer’s recommended stand!

Aquarium Water Weights


Below is a guide to glass saltwater and freshwater aquarium weights by volume:

AQUARIUMVOLUMESALTWATERWEIGHTFRESHWATERWEIGHTEMPTYWEIGHT
5 Gal / 19 liters43 lb. / 16 kg42 lb. / 19 kg7 lb. / 3 kg
10 gal. / 38 liters87 lb. / 40 kg84 lb. / 38 kg11 lb. / 5 kg
15 gal. / 57 liters128 lb. / 58 kg125lb. / 56 kg19 lb. / 9 kg
20 gal. / 76 liters172 lb. / 77 kg167 lb. / 75kg25 lb. / 11 kg
25 gal. / 95 liters214 lb. / 96 kg209 lb. / 94 kg32 lb. / 15 kg
30 gal. / 114 liters257 lb. / 116 kg250 lb. / 113 kg42 lb. / 19 kg
35 gal. / 133 liters300 lb. / 150 kg292 lb. / 131 kg46 lb. / 21 kg
40 gal. / 152 liters342 lb. / 154 kg334 lb. / 150 kg56 lb. / 25 kg
45 gal. / 170 liters385 lb. / 173 kg375 lb. / 169 kg68 lb. / 31 kg
50 gal. / 190 liters428 lb. / 193 kg417 lb. / 188 kg70 lb. / 32 kg
55 gal. / 208 liters 471 lb. / 212 kg459 lb. / 206 kg78 lb. / 35 kg
65 gal. / 246 liters 556 lb. / 250 kg542 lb. / 244 kg90 lb. / 41 kg
75 gal. / 284 liters642 lb. / 289 kg626 lb. / 281 kg98 lb. / 44 kg
90 gal. / 341 liters770 lb. / 346 kg 751 lb. / 338 kg135 lb. / 61 kg
120 gal. / 455 liters1027 lb. / 462 kg1001 lb. / 450 kg191 lb. / 87 kg
150 gal. / 569 liters1284 lb. / 578 kg1251 lb. / 563 kg281 lb. / 127 kg
180 gal. / 682 liters 1541 lb. / 693 kg1501 lb. / 676 kg282 lb. / 128 kg
210 gal. / 796 liters1798 lb. / 809 kg1751 lb. / 788 kg343 lb. / 156 kg
240 gal. / 910 liters2054 lb. / 924 kg2002 lb. / 901 kg365 lb. / 166 kg
280 gal. / 1061 liters2397 lb. / 1079 kg2335 lb. / 1051 kg402 lb. / 182 kg
300 gal. / 1137 liters2568 lb. / 1156 kg2502 lb. / 1126 kg446 lb. / 202 kg

Once you have the weight of the water you will also need to add the empty weight of the aquarium, the stand, the sand and the Live Rock/Dry Rock you add to the system.

How to Accurately Calculate Aquarium Weight & Volume

Calculating the weight and volume of your new aquarium is really simple and is essential for you to know. Knowing the weight is one part, but when it comes to dosing and treating your aquarium with medication, you need to know the volume in your system.

Knowing how to calculate volume will also help if you add on a future sump or frag tank to your system.


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Calculating Aquarium Volume:

Gallons:

48″ x 18″ x 21″ = 18,144 Cubic Inches18,144 x 0.004 = 73 Gallons

Litres:

122cm x 46cm x 53cm = 297,436 Cubic Centimeters297,436 / 1000 = 297 Liters

Calculating Aquarium Weight:

Pounds:

Volume ( Gallons ) x 8.56 for SaltwaterVolume ( Gallons ) x 8.34 for Freshwater73 Gallons x 8.56 = 625 lb. Saltwater73 Gallons x 8.34 = 609 lb. Freshwater

Kilogrammes:

Volume ( Litres ) x 1.024 for Saltwater Volume ( Litres ) x 1.000 for Freshwater

297 Litres x 1.024 = 304 kg for Saltwater297 Litres x 1.000 = 297 kg for Freshwater

Calculating Custom Shaped Aquariums

It’s back to Math Class Ladies & Gentlemen! Who can remember areas and volumes of shapes? It’s just the same here!

Calculate the areaCalculate the volumeCalculate the weight

Don’t worry I’m not going to be cruel and make you get out the pen, paper and calculator! There is an awesome calculator that does it all for you!

Click Here to visit the Volume Calculator

Once you have your volume, you can use the equations above to help you find out the weight. Don’t forget to add in the weight of your sump if that’s in the stand too!

Floor Strength Required For An Aquarium

When I was in the planning stages of my aquarium I knew it was going to be heavy. It’s only a 75 gallon aquarium, but I knew it was going to weigh around 650 lb., add the weight of the stand, sand, and rock, it would be close to 750-800 lb.

The other consideration I had was that people like to look at your aquarium when you have guests, so now you have 4- 6 adults standing in the same area and you have now added another 800-1200 lb. in weight.

A total weight of up to 2000 lb. within an 8ft square area of my floor. I’m no structural engineer but I wanted to know the floor in my 100-year-old house would take the load.

North American Building Code

Below my aquarium, I had a basement with my floor joists being 12″ apart. I researched and found that by placing the aquarium as close to the outside wall this would be the strongest point of the joists.Spanning as many joists as you can helps to distribute the load too.

A check of your local building codes will help you ascertain exactly what your floor should be able to support, but in general 12″ spans should support around 40 pounds per square foot. This is a theoretical load averaged over the entire floor within your room.

Your aquarium only takes up a small portion of the floor space and depending on where that floor space is, you may need to support the joists from below or have additional structure added to your joists.

If you looking to install a large aquarium I would suggest you contact a structural engineer to come and survey the location just to be sure.

How To Support Floor Joists For An Aquarium

Most aquariums up to the 120 Gallon size should be fine in most homes. Once you start going up from that size there are things you can do to help support the floor under your aquarium, provided you can access the area of course!

Place the aquarium close to an outside wallPlace your aquarium across as many joists as you can Install blocking or bridging between your joists to prevent twisting
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Joist Blocking and Bridging
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Joist Sistering
Install Sister boards to increase individual joist strengthInstall support beams and posts under joists
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Floor Joist Support

For my setup, I built an additional 2×4 frame and placed it under my joists to help support the load, just in case!


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Aquariums In Condo’s and Apartments

There are many aquarium owners who live in tower blocks who regularly ask this question. Is my aquarium too heavy for the concrete floor?As we all know concrete is incredibly strong and the floors of a residential and commercial tower block are built to suit.

During my research, all I have been able to find is that they must meet the same 40 pounds per square foot loading as residential homes. I have personally seen large aquariums over 120 gallons in offices and workplaces with no problems, but that doesn’t mean anything!

Two things to consider with tower buildings:

Have a structural engineer come and survey your space if you’re planning a big aquariumCheck with the rules and regulations of the tower block owners. They may limit the size of the aquarium you can install and may require you to have additional insurance to cover any leaks or damage.

Other Considerations

Many aquarium owners add a sump to their aquarium and where do many of these sumps get installed? In the stand, under the aquarium!

Now you have just added another 50 gallons of water and 400 lb. to your 150 gallon reef tank system!

In all my years in this industry, I have not come across anyone who’s floor has collapsed, but that’s not to say it has not happened. Like everything else in this hobby, Planning Is King!

The bigger the tank you can afford to run, the healthier and more stable it will be for its inhabitants but, make sure your floor is able to take the load. The last thing you want is to find out 5 years down the line the floor joists have started to split under your tank!

One last thing to consider is if you are in an earthquake zone. Is your tank stable, will it rock, will a dynamic load of a rocking tank add additional stress to your stand and floor structure?

These are just somethings you might want to consider when planning your next tank, as we all know we don’t go down in tank sizes ;D

Further Reading

You may find the following articles helpful too:


Richard

Hi, I"m Richard and I have been an avid aquarist for over 30 years with a passion for Saltwater Aquariums. I love to pass on my knowledge to help others get the same amount a pleasure out of this hobby as I do.View my About Me page to find out more about me & my mixed reef aquarium.


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About Me


My name is Richard and I have been an avid aquarist for over 25 years. My journey began, like many others, with the introduction of two goldfish and a small aquarium. I was hooked!It took me years of searching to help find all the best information to help me become successful with a Saltwater Aquarium.This site is designed to put all that helpful information in one easy-to-find place.