Why the same volume can stock differently
Two aquariums can hold a similar amount of water while providing very different horizontal swimming distance, bottom territory and air-water surface. StockingLab therefore carries the dimensions into the full planning model.
Gross volume is not the same as usable water
The glass-box calculation multiplies internal length, width and height, but a working aquarium rarely contains that full volume. Substrate, rocks, wood, equipment and the air gap below the rim displace water. StockingLab therefore shows a separate usable-water estimate rather than treating the advertised tank size as the exact amount of water supporting the animals.
Why footprint and surface area are separate outputs
Footprint is especially important for bottom-dwelling and territorial species because floor space cannot be replaced by extra height. Surface area matters because the air-water interface contributes to gas exchange. A tall narrow aquarium may therefore have the same gross litres as a longer tank while offering less horizontal swimming room and a different oxygenation margin.
Worked example
A 90 × 35 × 40 cm aquarium has a theoretical volume of 126 litres. In real use, the net water volume will be lower once substrate, decor and the fill line are accounted for. The 90 cm length and 3,150 cm² footprint also tell you something the 126-litre figure cannot: how much horizontal room and bottom territory the fish actually experience.
How to use the result for stocking
- Enter the aquarium's internal dimensions where possible rather than relying only on the manufacturer's rounded capacity.
- Use the full planner for fish selection because volume alone does not test social groups, compatibility, temperature, pH or swim-zone crowding.
- Keep a margin for decor displacement and avoid “filling” a tank to a calculated maximum.
- Recheck the plan if the actual tank dimensions differ materially from the nominal size used when choosing livestock.