The short answer
Roughly one kilogram per litre of water, plus the glass, substrate and rock on top. That means a 100 L tank weighs around 120 kg full, and it only climbs from there. Because all that weight sits in a small footprint, a full aquarium needs a properly rated stand and a floor that can bear it — this is not furniture you improvise.
Rough weights by size
- 20 L nano ≈ 25 kg
- 60 L ≈ 70–75 kg
- 100 L ≈ 120 kg
- 200 L ≈ 240 kg-plus
Add the glass, then your substrate and hardscape — gravel, sand and rock are dense and easily add tens of kilos to a larger tank. The water figure is the minimum, not the total.
Why the weight matters
That mass has two consequences. First, the stand and floor must carry it safely — over a suspended floor, position a big tank across the joists or above a load-bearing wall. Second, once filled the tank cannot be moved without draining, so decide placement first — see where to put an aquarium and how to move an aquarium.
Plan before you fill
Work out your full weight, choose a rated stand, confirm the floor can take it, then set up. Browse tanks on the aquariums hub or, for the big end, our best large aquarium picks.