Aquariums Are Heavy, But How Much Do They Weigh?


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!?

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

Filled Aquariums Weigh Around 8.56 lbs/gallon for Saltwater & 8.34 lbs/gallon for Freshwater. Purchasing the correct stand for the aquarium & knowing its weight before placing it on any surface will prevent the aquarium failing or collapsing. Floors need inspection before installing large aquariums.

Some Typical Full Aquarium Weights Are:

Tank VolumeFreshwater WeightSaltwater Weight
5 Gallons42 lbs / 19 kg 43 lbs / 19 Kg
20 Gallons167 lbs / 75 Kg172 lbs / 77 Kg
75 Gallons626 lbs / 281 Kg642 lbs / 289 Kg
120 Gallons1001 lbs / 450Kg1027 lbs / 462 Kg
240 Gallons2002 lbs / 901 Kg2054 lbs / 924 Kg

Do Bigger Aquariums Weigh Much More Than Small aquariums?

When considering the purchase of a new aquarium the size and weight are something you need to consider. Where do you want to install your new showpiece? In a wall, on a sideboard, on a shelf, on a set of drawers in your daughter’s bedroom? All of these places can work out great so long as they are designed to take the weight of the aquarium.

Pretty much every aquarium manufacturer designs and builds beautiful stands and canopies to house your aquarium that are purposely engineered to take the full weight of the aquarium.

When you look at building your own stand or frame then you need to do some math to ensure your supporting structure will be able to handle the weight.

Aquarium Water Weight Examples

Below is a rough guide to Salt and Fresh water weights by volume:

Aquarium Weight Guide

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.

Multiply Length x Width x Height

Aquarium Dimension Guide

Calculating Aquarium Volume:

Gallons:

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

Litres:

122cm x 46cm x 53cm = 297,436 Cubic Centimeters
297,436 = 297 Litres

Calculating Aquarium Weight:

Pounds:

Volume ( Gallons ) x 8.56 for Saltwater
Volume ( Gallons ) x 8.34 for Freshwater

73 Gallons x 8.56 = 625 lbs Saltwater
73 Gallons x 8.34 = 609 lbs Freshwater

Kilogrammes:

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

297 Litres x 1.024 = 304 Kg for Saltwater
297 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!

  1. Calculate the area
  2. Calculate the volume
  3. Calculate 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 <== (opens in a new tab)">==> 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 lbs, add the weight of the stand, sand, and rock, it would be close to 750-800 lbs.

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 800-1200lbs in weight.

A total weight of up to 2000lb 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 wall
  • Place your aquarium across as many joists as you can
  • Install blocking or bridging between your joists to prevent twisting
Joist Blocking and Bridging
Joist Blocking and Bridging

Joist Sistering
Joist Sistering

  • Install Sister boards to increase individual joist strength
  • Install support beams and posts under joists
Floor Joist Support
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!

Aquarium Joist Bracing

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 aquarium
  • Check 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 lbs 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.

Recent Posts