CO2: KH/PH Chart
PH is a result of carbonate hardness (KH) and CO2 concentration, meaning that we can calculate the amount of CO2 in a body of water by measuring KH and PH. For most of our tanks KH is stable while PH varies according to CO2 levels. As CO2 levels increase the PH goes down. By cross referencing your KH and PH values in the table below you can quickly find out the CO2 concentration in your tank.
| pH |
6.0 |
6.2 |
6.4 |
6.6 |
6.8 |
7.0 |
7.2 |
7.4 |
7.6 |
7.8 |
8.0 |
| KHº |
|
|
|
|
|
|
|
|
|
|
|
| 0.5 |
15 |
9.3 |
5.9 |
3.7 |
2.4 |
1.5 |
0.9 |
0.6 |
0.4 |
0.2 |
0.1 |
| 1.0 |
30 |
18.6 |
11.8 |
7.4 |
4.7 |
3 |
1.9 |
1.2 |
0.7 |
0.47 |
0.3 |
| 1.5 |
44 |
28 |
17.6 |
11.1 |
7 |
4.4 |
2.8 |
1.8 |
1.1 |
0.7 |
0.4 |
| 2.0 |
59 |
37 |
24 |
14.8 |
9.4 |
5.9 |
3.7 |
2.4 |
1.5 |
0.9 |
0.6 |
| 2.5 |
73 |
46 |
30 |
18.5 |
11.8 |
7.3 |
4.6 |
3 |
1.9 |
1.2 |
0.7 |
| 3.0 |
87 |
56 |
35 |
22 |
14 |
8.7 |
5.6 |
3.5 |
2.2 |
1.4 |
0.9 |
| 3.5 |
103 |
65 |
41 |
26 |
16.4 |
10.3 |
6.5 |
4.1 |
2.6 |
1.6 |
1 |
| 4.0 |
118 |
75 |
47 |
30 |
18.7 |
11.8 |
7.5 |
4.7 |
3 |
1.9 |
1.2 |
| 5.0 |
147 |
93 |
59 |
37 |
23 |
14.7 |
9.3 |
5.9 |
3.7 |
2.3 |
1.5 |
| 6.0 |
177 |
112 |
71 |
45 |
28 |
17.7 |
11.2 |
7.1 |
4.5 |
2.8 |
1.8 |
| 8.0 |
240 |
149 |
94 |
59 |
37 |
24 |
14.9 |
9.4 |
5.9 |
3.7 |
2.3 |
| 10 |
300 |
186 |
118 |
74 |
47 |
30 |
18.6 |
11.8 |
7.4 |
4.7 |
3 |
| 15 |
440 |
280 |
176 |
111 |
70 |
44 |
28 |
17.6 |
11.1 |
7 |
4.4 |
| 20 |
590 |
370 |
240 |
148 |
94 |
59 |
37 |
24 |
14.8 |
9.4 |
5.9 |
The ideal CO2 concentration for a CO2 enriched tank is anywhere between 15ppm and 30ppm (ppm = mg/lt). To simplify things the ideal range is highlighted in green. Red values indicate a CO2 level that is too high and potentially dangerous.
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