How Much Does a Fish Tank Weigh? Full and Empty Weight by Gallon
A filled aquarium weighs about 11 to 13 lb per gallon once glass and gravel are counted: a 20 gallon is about 225 lb, a 55 about 610 lb.
By the PawReckon team Β· Published
A fish tank weighs much more than its water. Count the glass and a normal gravel bed and a freshwater aquarium comes in at 11.1 to 12.8 lb per gallon: a 10 gallon is about 117 lb set up, a 20 gallon about 225 lb, a 55 gallon about 609 lb and a 125 gallon about 1399 lb. Water alone is 8.34 lb per US gallon, and that is the number most charts stop at, which is how people end up putting a 600 lb tank on a dresser rated for clothes.
The table below adds up the three parts for every standard glass size, then the sections after it cover saltwater, rock, the stand and the floor.
Fish tank weight chart, 5 to 125 gallons
Each total is empty glass plus the nominal gallons of fresh water plus a 2 inch bed of gravel or sand at 100 lb per cubic foot. Counting the full nominal gallons is a slight overestimate, because substrate and the gap below the rim take up some of that water. For a stand or a floor, overestimating is the right direction to be wrong in.
| Tank | Inside size (in) | Empty | Water | Gravel | Full | Full, salt |
|---|---|---|---|---|---|---|
| 5 gallon | 16 Γ 8 Γ 10.5 | 7 lb | 42 lb | 15 lb | 64 lb | 65 lb |
| 10 gallon | 20 Γ 10 Γ 12 | 11 lb | 83 lb | 23 lb | 117 lb | 119 lb |
| 20 gallon (20 high) | 24 Γ 12 Γ 16 | 25 lb | 167 lb | 33 lb | 225 lb | 229 lb |
| 20 gallon (20 long) | 30 Γ 12 Γ 12 | 25 lb | 167 lb | 42 lb | 234 lb | 238 lb |
| 29 gallon | 30 Γ 12 Γ 18 | 40 lb | 242 lb | 42 lb | 324 lb | 330 lb |
| 40 gallon (40 breeder) | 36 Γ 18 Γ 16 | 58 lb | 334 lb | 75 lb | 467 lb | 475 lb |
| 40 gallon (40 long) | 48 Γ 13 Γ 16 | 55 lb | 334 lb | 72 lb | 461 lb | 469 lb |
| 55 gallon | 48 Γ 13 Γ 21 | 78 lb | 459 lb | 72 lb | 609 lb | 620 lb |
| 75 gallon | 48 Γ 18 Γ 21 | 140 lb | 626 lb | 100 lb | 866 lb | 881 lb |
| 90 gallon | 48 Γ 18 Γ 24 | 160 lb | 751 lb | 100 lb | 1011 lb | 1029 lb |
| 125 gallon | 72 Γ 18 Γ 21 | 206 lb | 1043 lb | 150 lb | 1399 lb | 1425 lb |
In kilograms: a 20 gallon is about 102 kg full, a 29 gallon (109.8 liters) about 147 kg, a 55 gallon about 276 kg and a 75 gallon about 393 kg.
Where the weight comes from
Water is most of it, and it is fixed. A US gallon of fresh water weighs 8.34 lb at room temperature. That does not change with the brand of tank or what you keep in it, so the gallon number on the box gets you most of the way: 459 of the 609 lb in a set-up 55 gallon is water.
Glass is the part that surprises people on small tanks. The empty weights in the chart are typical retail figures for standard rimmed glass. On a 55 gallon the glass is 13% of the total. On a 5 gallon it is 11%, because small tanks still need panels thick enough to handle and ship. That is why the per-gallon figure is highest at the small end. Glass weight tracks panel area and thickness, not just volume: the 75 gallon has the same 48 by 21 inch front as the 55 but is 62 lb heavier empty, from the wider bottom and side panels and thicker glass. A rimless tank of the same size is often heavier still, because rimless panels are cut thicker; an acrylic one is roughly half the weight of glass.
Substrate scales with the floor, not the gallons. Gravel and sand weigh about 100 lb per cubic foot dry, so the weight depends on footprint and depth. On a 75 gallon (48 Γ 18 inches of floor) each inch of depth is worth about 50 lb:
| Substrate depth, 75 gallon | Weight |
|---|---|
| 1 inch | 50 lb |
| 2 inches | 100 lb |
| 3 inches | 150 lb |
| 4 inches | 200 lb |
A planted tank with a 3 to 4 inch sloped bed carries noticeably more than the chart's 2 inches. The same footprint logic is why the 20 long (42 lb of gravel) outweighs the 20 high (33 lb) when both are full: same water, more floor.
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Saltwater and reef tanks
Seawater at normal reef salinity has a specific gravity of about 1.025, so it weighs about 8.55 lb per gallon instead of 8.34. On a 75 gallon that is 15 lb extra, which matters less than it sounds. The real difference on a reef is live rock, which hobbyists usually budget at 1 to 1.5 lb per gallon: another 75 to 113 lb on a 75. Add a sump under the stand and a 75 gallon reef can pass 994 lb before anyone has bought a fish.
What the weight means for the stand
Aquarium stands are built for a load that is heavy, constant and has to stay perfectly level. Furniture is not. A dresser or bookshelf may hold the weight on day one, but particleboard creeps under a steady load, and the first thing it does is sag in the middle. A glass tank resting on a surface that is no longer flat puts stress into the bottom seams, and that is how tanks fail months after they were set up.
- Use a stand rated for the tank size, or for the next size up. The stand should support the full perimeter of a rimmed tank's frame.
- Level it before you fill it. A tank that is level empty will be level full only if the stand and floor do not move. Check with a spirit level across both lengths and the diagonal, then again a day after filling.
- Fill it where it will live. A 20 gallon at 225 lb cannot be moved full by two people safely, and even fully drained the glass and wet gravel are still around 58 lb. Moving a tank with water in it also flexes the seams.
- Count the stand itself. A typical wooden stand for a 75 gallon weighs around 60 lb, which puts the whole assembly at about 926 lb on four legs or a plinth.
Will my floor hold a fish tank?
For most tanks up to 55 or 75 gallons on a sound modern floor, yes, and people keep them on upper floors all the time. The number that worries people is the load on the footprint: a full 55 gallon puts about 141 lb on each square foot it covers, and US residential floors are designed for a uniform live load of 40 lb per square foot in living areas and 30 in bedrooms. That comparison looks alarming (3.5 times the design load) but it is the wrong one, because the design load is spread across the whole room, while joists share a concentrated load with their neighbours and the subfloor spreads it.
What actually changes the risk:
- Orientation. Run the long side of the tank across the joists, not along them, so the weight lands on several joists instead of one or two.
- Position. Against an exterior or load-bearing wall the joists are at their strongest, near their support. The middle of a long span is where the floor flexes most.
- Size. At 125 gallons (1399 lb before the stand) and up, or on an older floor that already bounces or sags, get a builder or structural engineer to look before you fill it. This article is arithmetic, not a structural assessment.
How to work out your own tank's weight
- Find the real volume. Measure inside the glass and run it through the aquarium volume calculator. The nominal size on the label is a round number; the shape pages, like bowfront or cylinder, show how to measure the awkward ones.
- Multiply by 8.34 for fresh water, or 8.55 for salt.
- Add the empty weight from the label or the chart above.
- Add the substrate: floor area in square feet Γ depth in inches Γ about 8.3 lb. Then rock, the stand and any sump.
If you are sizing a tank for a particular spot, weight and stocking are linked: a bigger tank is heavier but holds far more fish per gallon of margin. The 20 gallon stocking guide shows what fits in the most common size, and the stocking calculator will tell you what any tank holds once you know its gallons. Whatever size you pick, cycle it before adding fish.
Weight, dimensions and stocking by size
Each size page breaks the weight down for its own footprint and lists what it comfortably stocks.
- 5 gallon tankAbout 64 lb full, 7 lb empty
- 10 gallon tankAbout 117 lb full, 11 lb empty
- 20 gallon tankAbout 225 lb full, 25 lb empty
- 29 gallon tankAbout 324 lb full, 40 lb empty
- 40 gallon tankAbout 467 lb full, 58 lb empty
- 55 gallon tankAbout 609 lb full, 78 lb empty
- 75 gallon tankAbout 866 lb full, 140 lb empty
- 90 gallon tankAbout 1011 lb full, 160 lb empty
- 125 gallon tankAbout 1399 lb full, 206 lb empty
Frequently asked questions
How much does a 20 gallon fish tank weigh?
About 225 lb set up: 25 lb of glass, 167 lb of water and 33 lb for a 2 inch gravel bed. The 20 long weighs about 234 lb because its bigger floor takes more gravel. Empty, either one is about 25 lb.
How much does a 55 gallon fish tank weigh full?
About 609 lb with fresh water and 2 inches of gravel, or 276 kg. The water alone is 459 lb, the empty glass about 78 lb. As a saltwater tank it is about 620 lb before any live rock.
How much does a 75 gallon fish tank weigh?
About 866 lb full of fresh water with a 2 inch gravel bed, 140 lb empty. Put it on a typical 60 lb wooden stand and the floor carries about 926 lb.
How much does a 10 gallon fish tank weigh?
About 117 lb set up and 11 lb empty. The water is 83 lb of that.
Is there a quick rule for aquarium weight?
Multiply the gallons by 12 for a freshwater tank with glass and gravel included. Across the standard sizes the real figure runs from 11.1 to 12.8 lb per gallon, higher on small tanks because the glass is a bigger share of the total.
Is a saltwater tank heavier than a freshwater one?
Yes, by about 2.5 percent on the water: seawater at a specific gravity of 1.025 weighs about 8.55 lb per gallon. On a 75 gallon that is 15 lb more. Live rock is the bigger difference, often 1 to 1.5 lb per gallon on a reef.
Keep going with the same pet
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