What makes an aquarium heavy
Water is by far the biggest part: about 8.34 lb per US gallon (1 kg per liter), and saltwater around 2.5% more. A tank also carries the weight of its glass, substrate, rock and equipment, and the stand on top of that.
How the estimate works
- Glass: area of the bottom and four sides × thickness × 2.5 g/cm³ (the density of glass). Frames, braces and lids are not included.
- Water: inside dimensions × water height (height − bottom glass − gap − substrate).
- Substrate: inside footprint × depth × 1.6 kg/L, a typical value for sand and gravel.
Rock, wood, equipment and the stand are extra. Live rock and hardscape can easily add another 10–20% in reef or iwagumi setups.
Example
A standard 55 gallon tank (48 × 13 × 21 in, ¼" glass) with 2" of sand comes to roughly 520 lb filled. On its 4.3 sq ft footprint that is around 120 lb per square foot, well above what a residential floor is typically designed for over a large area, which is why large tanks are best placed near a load-bearing wall and across the floor joists.
Frequently asked questions
How much does a 55 gallon aquarium weigh when full?
Roughly 500–650 lb including water, glass and substrate, depending on the water level, substrate and decor. The stand adds more.
How much does a 75 gallon aquarium weigh?
A 75 gallon (48 × 18 × 21 in) typically weighs around 700–850 lb filled with substrate and rock. Enter your exact setup above.
Can my floor hold my aquarium?
Smaller tanks are rarely a problem. For large tanks, place them against a load-bearing wall and perpendicular to the joists, and consult a structural engineer if in doubt.