I would like to different CO2 concentration into different algal culture but I don't know how can calculate it. Does it need specific regulator of I can calculate it from the flow rate of the CO2 cylinder?
A regulator is needed to issue out the gas from its cylinder. As you need to estimate CO2 level in different culture waters, it depends upon various factors like speed of bubbling, whether diffuser stone used, the column of water through which the gas will pass through, the temperature of medium & TDS of the medium.
If any of the parameters alter, then the result will also alter.