An example will best illustrate the significance of these pro[>ortions and the mode of 

 carbon dioxide regulation. 



At an ii.C.C. i-ate of 2.0 — v/hich corresponds with a CaO-content of about So milligrams 

 per liter — the v/ater, according to table 7 contains iJJj iiillisrams per liter bicarbonate 

 carbon dioxide and 2.3 milligrams per liter "corresponding" free carbon dioxide. 



ciun bicarbonate 



These normal proport.ious between the slightly alkaline reacting cal 

 and the slightly acid carbon dioxide lead to a "nor.nal pH rate" of 8,1. 



I>i0T.', if through the assimilation process of plants the vrater loses 1 milligraaa free 

 carbon dioxide, the pH rate rises on account of this great loss in acid pi-op?rties. At 

 the same tiine, a certain amount of calcium bicarbonate breaks up into calcium carbonate 

 and free carbonic dioxide until a new equilibrium, vdth a corresponding pH rate has been 

 established. 



The calcium carbonate is then deposited in concentrated foim upon the plants or into 

 the v/ater — since only 13 milligrams CaC03 are soluble in carbon dioxide — free water — and 

 sinks to the bottom of the pond. 



The A.C.C. naturally drops proportionally; a biogenical decalcification has taken 

 place. The introduction of caustic lime has the same effect, by absorbing carbon dioxide. 



On the other hand, when carbon dioxide is produced so that the water contains more 

 than 2.3 milligrams per liter of free carbon dioxide vdth a corresponding subnormal pH 

 rate, the aggressive excess carbon dioxide dissolves the calcium carbonate — deposited 

 upon the plcmts or at the bottom of the pond — into calcium bicarbonate. The A.C.C. rises 

 until the equilibrium has been reached and the pH rate has become normal again. 



A lime enrichment process of the T;ater has taken place. In other words, Te deal 

 here with a reversible process which can be expressed in the following equation: 



Ca (HC03)2 > CaC03 -f CO2 -^ H2O 



(dissolved calc. bicarbonate) ^ (net undissolved (carbon dioxide) (v;ater) 



calc. carbonate) 



Such metabolic processes — in one or the other direction — talce place continuously in 

 a pond, and since this is the case one cannot expe ct the pH rate — .just as t he oxygen rate — 

 to remain normal at all times , the less so since through the presence of other mineral 

 combinations the pH rate can undergo slight variations. 



Ptee carbon dioxide and bicarbonate carbon dioxide form a great nutritional supply 

 for plants. For this reason, carbon dioxide can never reach a minimum, as Ion p. as the 

 ^•C.C. is_ sufficient (over about 0.6) and the pH rate is not too hi^ch . This fact was 

 completely unknov^Ti 1$ years ago and is even today still quite often ignored . 



i«atui-ally, tlie carbon dioxide supply is the greater, the regulation of its rate and 

 of the pH rate the better, the higher the amount of bicarbonate, i.e. the calcium bicar- 

 bonate content with its corresponding A.C.C. 



But the rise in the rate of bicarbonate carbon dioxide is not the only deciding 

 factor here since — as shown b;/^ table 7 — the "corresponding" free carbon dioxide rate 

 rises at the same tiae and relatively even higher. 



At an A.C.C. rate of 0.5, we have a proportion of 220:1, but at an A.C.C. rate of 4., 

 this proportion of bicarbonate carbon dioxide to free carbon dioxide is only 11:1. 



If the absolute cont ent of "corresponding" free carbon dioxide is at the same time very 

 high, the introduction or elimination of 1 milligraia free carbon dioxide will react upon 

 the nonnal proportions only very slightly. The maintenance of the pH rate in waters v/ith a 

 high A.C.C. (calcium content) is ultimately due to this ciraLmstance. 



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