But also a strong Increase in the pH rate is possible and not onl7 through inflow of 

 trade waste but from natural causes, such as the consumpticMi of carbonic acid through 

 assimilatijag plants. 



It is possible for water plants — in "lime oligotrophic ponds" when the carbonic acid 

 rate is low on account of a lowered acid combination capacity — to so completely drain 

 carbonic acid from the calcium bicarbonate contents that only calcium hydrood.de (mild 

 caustic) remains. 



Upon the shores of the Muggel Lake, I could determine a pH rate of over 12, i.e. in 

 the water above the growing submarine flora, and under the most favorable conditions of 

 a water temperature of 31 centigrades and of strong sunlight. 



The " alkaline danger point " . which presumably lies around 9 was therefore certainly 

 over-reached. Such conditions, of course, will nomally occur only during the afternoon 

 hours of certain days and under especially favorable conditions. The fish have then the 

 chance to retreat into deeper waters until conditions become normal again duilng the 

 night, 



I wish to emphatically state that it is erroneous to presume that strongly calcifer- 

 ous waters have a high pH rate. i.e. are especially alkaline. Rather the opposite is true. 



Highly calciferous waters merely maintain a more steady pH rate, around 7 to 8, The 

 sufficiently high acid-ccatbining. power prevents pH variations. 



At the hatcheries pf the Forest Academy in Eberswalde, where the acid couijination 

 capacity varies between 3 and U (on account of a CaO- content of from 84. to 100 milligraa 

 per liter), I could mostly find a pH rate between 7.4 and 7.8, and never over 8.6 or be- 

 low 6.95, although my tests were done regularly and even under extreme weather conditions 

 (tenperature up to 30 degrees centigrade). At a calcium CaO rate of from 150 to 200 

 milligram per liter, I always found a pH rate of between 7 and 8, as was theoretically 

 to be expected. 



For the fishbreeders use, we have condensed here our findings anent the importance of 

 the pH rate into a short table. Statements with regard to "normal pH rate" in waters of 

 different calcium contents will be found upon page 5fc. 



Table 5. 



pH value 



water reaction 



pond-cultural evaluation 



Alkaline danger point. Can sometimes 

 occur in summer and when the acid com- 

 strongly alkaline bination capacity (A.C.C.) is low, and 



in plant covered ponds. Addition of lime 

 (CaCo 3) often to be recommended. 



.0) 

 .0) 



8.5) 

 8.0) 

 7.5) 

 7.0) 



slightly alkaline 

 neutral 



Normal reaction and latitude of variation 

 of good pond waters with medium and high 

 A.CC. addition of lime not necessary as 

 long as limits not over-reached or disease 

 germs not to be combated. 



Reaction of bad waters with low A.CC. in 

 6,5) heath and moor regions. Great danger of 



6.0) slightly acid iVirther lowering of pH rate. pH rate must 

 5,5) be continuously watched. Addition of lime 



urgently recommended. 



Acid danger point . A.CC. always very low. 

 5,0) strongly acid Deadly for pond fish and their eggs if kept 

 4.5) in such v/aters for any length of time. 



Should be dosed with lime Immediately. 



4.0) 

 4.0) 



very 

 strongly acid 



Water unsuitable for fish breeding. 

 A.CC. negative. Improvement of water 

 through lime almost always useless. 



