The Planted Tank Forum - View Single Post - pH Drop CO2 accuracy
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post #9 of (permalink) Old 10-03-2019, 01:57 AM Thread Starter
Edward
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@Dianna Walstad published the concentration of atmospheric CO2 equilibrium with water, based on reference by Wetzel RG. 1983. Limnology (Second Ed.). Saunders College Publishing (Philadelphia, PA), p. 202 as 0.5 mg/l, (0.5 ppm). Ecology of the Planted Aquarium, page 100, “Water in equilibrium with air contains 0.5 mg/l CO2”.

The widely used pH drop idea to control water concentration of CO2 is based on equilibrium of 3 ppm. Recommended 1 pH drop represents 3 x 10 = 30 ppm CO2. However, if Dianna Walstad reference is correct then people actually have 0.5 x 10 = 5 ppm CO2. The reason why 0.5 ppm is actually possible is because people often have 1.6 pH drop and healthy fish at the same time. The pH drop of 1.6 is 20 ppm CO2, instead of 120 ppm CO2 at 3 ppm degassed.

Code:
0.5 degassed ppm
pH drop  CO2 
1.0        5
1.1        6
1.2        8
1.3       10
1.4       13
1.5       16
1.6       20
1.7       25
1.8       32
1.9       40
2.0       50

3.0 degassed ppm
pH drop  CO2
1.0       30
1.1       38
1.2       48
1.3       60
1.4       75
1.5       95
1.6      120
1.7      150
1.8      189
1.9      238
2.0      300
Anyone have any information on where the original degassed 3 ppm CO2 came from?


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Last edited by Edward; 10-03-2019 at 01:57 AM. Reason: ...
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