A filled aquarium is one of the heaviest things in a home. Water weighs about 8.3 lb per US gallon (1 kg per liter), and the glass, gravel and rock add to that. A quick rule is about 10 lb per gallon for a set-up tank; the table below gives figures for each standard size.
Filled weight by tank size
| Tank | Water | Glass | Gravel (2 in) | Total | Per ft² of footprint |
|---|---|---|---|---|---|
| 10 gallon | 66 lb | 13 lb | 22 lb | 102 lb | 73 lb |
| 20 gallon high | 135 lb | 26 lb | 32 lb | 192 lb | 96 lb |
| 29 gallon | 194 lb | 33 lb | 40 lb | 267 lb | 107 lb |
| 40 gallon breeder | 305 lb | 51 lb | 72 lb | 428 lb | 95 lb |
| 55 gallon | 399 lb | 68 lb | 69 lb | 536 lb | 124 lb |
| 75 gallon | 549 lb | 103 lb | 95 lb | 748 lb | 125 lb |
| 90 gallon | 628 lb | 143 lb | 94 lb | 866 lb | 144 lb |
| 120 gallon | 848 lb | 164 lb | 127 lb | 1 138.1 lb | 142 lb |
Estimates for typical glass thickness, water 1 inch below the rim and a 2 inch gravel bed. Rock, wood, equipment and the stand are not included; a stand alone can weigh 50–150 lb.
How the numbers are worked out
- Water: the real water volume (inside the glass, below the rim) times 8.34 lb per gallon, less the space the gravel's grains take up.
- Glass: the area of the five panes times their thickness times the density of glass (about 2.5 kg per liter). Framed tanks add a few pounds of plastic trim.
- Gravel: footprint × depth × about 100 lb per cubic foot. The substrate calculator does this for other depths and materials.
For example, a 55 gallon holds about 51 gallons of water (399 lb with the gravel in), carries 68 lb of glass and 69 lb of gravel: about 536 lb before rock and the stand.
Choosing a stand
Use a stand made for aquariums and rated for the tank's size. Furniture that looks sturdy is usually designed for a few dozen pounds spread over a shelf, not hundreds of pounds on its edges. The stand must support the whole bottom frame of a framed tank, and be level: a tank that is out of level loads one corner and one seam more than the rest.
Is my floor strong enough?
A filled tank concentrates its weight on a small footprint: the "per ft²" column above is often over 100 lb per square foot, while US residential floors are typically designed for a live load of around 40 lb per square foot spread over the room. In practice, small and mid-size tanks are fine on a sound floor, because the joists spread the load. For large tanks (roughly 75 gallons and up), place the tank across the joists rather than along them, as close to a load-bearing wall as you can, and ask a builder or structural engineer if the floor is old, springy or over a long span.
Moving a tank
Never move a tank with water in it. Even a few inches of water adds a lot of weight and strains the seams. Drain it, keep the fish and filter media in tank water, and move the empty glass with the gravel removed or nearly so.