The Free On-line Aquaculture Dictionary

Bath Treatment Calculation Example
Example  - Formalin @ 200ppm to a tank 7.5m diameter and 2m deep
Calculate the volume of water in the tank:
Area = 3.1415 x radius2 x depth
          = 3.1415 x (7.5/2)2 x 2
          = 88.35m3
          = 88,350,000 millilitres
Volume of chemical required = (volume ml / 1000000) x concentration (ppm or mg/l)
          = (88,350,000 / 1,000,000) x 200
          = 17,670 millilitres formalin
Therefore to dose the tank with 200ppm of formalin requires 17,670 ml (or 17.67 litres) of formalin.
Note that the above calculation also works for chemicals dosed by weight as mg/l. 1 ml should be taken as the equivalent of 1 mg.