Only the transport form of the pressurised gas cylinder is interesting for aquaristics. Liquid CO2 and dry ice are probably unsuitable for aquaristic purposes and are also oversized.


According to the applicable labelling regulations, CO2 compressed gas cylinders must be grey. They are filled with CO2 (liquid - cold or pressurised pump) on the scale. Depending on the outside temperature, a pressure of 45 to 60 bar is reached.


In Germany, a filling factor of 0.75 (filling ratio 1 : 1.34) is used in warm southern countries with a filling factor of 0.66 (filling ratio 1 : 1.50, see diagram).

The density of liquid CO2 is approx. 1 g/cm3 and is therefore at the same level as water. If the temperature and pressure increase, the liquid carbon dioxide expands. At 22.2 °C and 59.3 bar, the bottle is 100 % filled with liquid. If the temperature increases further, the pressure rises extremely quickly. At 50 °C it is already 180 bar.

For this reason, the maximum bottle pressure is set at 250 bar (old bottles 190 bar with burst protection).


With a few exceptions, withdrawal may only take place via a pressure reducer. The cylinder pressure of 45 - 60 bar will burst even the most stable installations!
The cylinder must always be in a vertical position. If liquid CO2 enters the pressure reducer directly, the full cylinder pressure may be present on the consumption side under unfavourable circumstances!