Since water towers generally have a very large capacity, I would say that cubic meters might be the best bet. You can measure the total volumetric capacity of the water tower in cubic meters and then determine the volume of water that is currently in the water tower. However, an amount of water can also be measured in liters.
Litres for a domestic aquarium, kilolitres for a large [public] aquarium.
metric unit
Litre
millimetres.
its liters
Gallons (standard) or liters (metric).
The volume of the bottle would be in litres.
Litres for a domestic aquarium, kilolitres for a large [public] aquarium.
metric unit
Litre
In metric unit of the amount of liquid in a water bottle holds
It depends on the amount of water. In the metric system, water would be measured by liters, with a prefix if needed (Kilo, Hecto, Deca, etc.)
Litres.
millimetres.
mL, L, cm3, m3 are all SI units that can be used to measure the volume of water.
In liters
its liters