G 



Appendix 



Chemical Treatments: 

 Calculations and Constant 

 Flow Delivery 



Hatchery systems often receive prolonged- bath or constant-flow chemical 

 treatments that adjust water quality or control diseases. In prolonged-bath 

 treatments (without water flow), chemicals are spread over the surface of 

 the water body, and mixed throughout its volume, by hand or machine. 

 Many hatchery tanks and most ponds, particularly large ones, are treated 

 statically. In constant-flow treatments, chemicals are metered at one point 

 into continously renewed water supplies; the turbulence of the moving 

 water accomplishes the mixing. Constant-flow treatments typically are used 

 in intensive culture when even a temporary halt in the supply of fresh 

 water might cause fish mortality because of oxygen depletion or waste 

 accumulation. 



Chemical applications normally are couched in terms of final concentra- 

 tions; a pond treatment of 2 parts per million rotenone means the whole 

 pond should contain this concentration after application. Concentrations, 

 in turn, typically are weight ratios: weight of chemical in solution (or 

 suspension) per weight of solvent (usually water). The ratio may be 

 expressed in terms either of unit solvent weight or of unit solute weight. 

 Ten pounds chemical per ton of water, and one pound chemical per 200 

 pounds water (l:200), both represent the same concentration. Even when a 

 concentration is expressed in terms of volume or capacity (pounds/acre- 

 foot; milligrams/liter), it is the equivalent weight of that volume of water 

 that is implied. 



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