The Relationship of CO2, pH and KH

KH/pH 6.0 6.2 6.4 6.6 6.8 7.0 7.2 7.4 8.0
0.5 15 9.3 5.9 3.7 2.4 1.5 0.9 0.6 0.2
1.0 30 19 12 7 5 3 1.9 1.2 0.3
1.5 44 28 18 11 7 4 2.8 1.8 0.4
2.0 59 37 24 15 9 6 4 2.4 0.6
2.5 73 46 30 19 12 7 5 3 0.7
3.0 87 56 35 22 14 9 6 4 0.9
3.5 103 65 41 26 16 10 7 4 1.0
4.0 118 75 47 30 19 12 6 5 1.2
5.0 147 93 59 37 23 15 9 6 1.5
6.0 177 112 71 45 28 18 11 7 1.8
8.0 240 149 94 59 37 24 15 9 2.4
10 300 189 118 74 47 30 19 12 3
15 440 280 176 111 70 44 28 18 4
Blue = Low CO2, less than 10 ppm Green = Ideal/target CO2 levels, 10 to 25 ppm Yellow = Stressful/harmful to fish, 25 to 35 ppm Red = Potentially lethal to fish, 35> ppm