yS MAINTAINING FISHES 



9.2 to 9.8. It is desirable to adjust this pH to a lower 

 value by the addition of hydrochloric acid or citric 

 acid. Citric acid has the advantage of permitting pre- 

 mixing of the buffer and acid. The amount of buffer 

 added is determined by a number of variables. Mc- 

 Farland and Norris' work was done with salt-water 

 forms. The desired pH range for these forms is from 

 7.5 to 8.5. Since these values are within the range 

 tolerated by fresh water forms, they are given here. 

 For more Hmited buffering use 5 grams of tris-buffer 

 per gallon plus 2.35 ml. of hydrochloric acid or 2.0 

 grams of citric acid. For a high buffer capacity use 

 15 grams of tris-buffer per gallon plus 6.40 ml. of 

 hydrochloric acid or 14.11 grams of citric acid. The 

 pH of the treated water should then be determined 

 and if it is too high, i.e., above 8.5 it should be ad- 

 justed by the addition of more acid. 



Sealed tanks appear to affect the amount of carbon 

 dioxide dissolved in transport tank water. Haskell and 

 Davies (1959) measured the effect of sealing a tank 

 containing three pounds of trout per gallon. An hour 

 after the tank was sealed the carbon dioxide reached 

 a concentration of 31.3 p.p.m. When the tank was 

 opened the carbon dioxide concentration dropped to 



5.3 p.p.m. in one-half an hour. 



Water cannot be hauled too satisfactorily in un- 

 sealed tanks, but it is obvious that some means of 

 removing stagnant air from above the water surface 

 is desirable. In circulated tanks a venturi can be used 

 to introduce air into the water, and an air escape pipe 

 can be installed in the top of the tank. On non- 

 circulated tanks that are transported on an open truck 



