CO2 Table

Due to many enquiries about what is the right pH value for an aquarium, if CO2 is to be supplied, here's a table that corellates pH with Carbonate Hardness (KH). KH is the key factor in adjusting pH values to get the amount of CO2 right. This is because carbonates act as buffers and will offset your CO2 content. 

Note: pH Tests will roughly match the colours in the table: Go for a turquoise green for optimum CO2.

Note: The correct pH depends on the Carbonate Hardness (KH) of your water:

CO2-content (mg/l)in Relation to Carbonate Hardness (KH) and pH

 
    too much CO2
     CO2 OK
     too little CO2

pH-Wert
KH 6.3 6.4 6.5 6.6 6.7 6.8 6.9 7 7.1 7.2 7.3 7.4 7.5
2 32 25 20 16 13 10 8 6 5 4 3 3 2
3 48 38 30 24 19 15 12 10 8 6 5 4 3
4 64 51 40 32 25 20 16 13 10 8 6 5 4
5 80 63 50 40 32 25 20 16 13 10 8 6 5
6 96 76 60 48 38 30 24 19 15 12 10 8 6
7 111 89 70 56 44 35 28 22 18 14 11 9 7
8 127 101 80 64 51 40 32 25 20 16 13 10 8
9 143 114 90 72 57 45 36 29 23 18 14 11 9
10 159 126 100 80 63 50 40 32 25 20 16 13 10
11 175 139 111 88 70 55 44 35 28 22 18 14 11
12 191 152 121 96 76 60 48 38 30 24 19 15 12
13 207 164 131 104 82 65 52 41 33 26 21 16 13
14 223 177 141 112 89 70 56 44 35 28 22 18 14

Measure your Carbonate Hardness and match with a medium range CO2-content (green band), e.g. 20 mg/l. Then, read off the corresponding pH value and adjust your dosage accordingly.