21
UK
12 How much CO
2
is needed?
12.1 pH level, CO
2
and carbonate hardness (KH)
The three parameters, pH value, CO
2
content and carbonate hardness, are inseparably linked,
as they are interdependent.
When CO
2
comes into contact with water, a certain amount of carbon dioxide is produced which
reduces the pH value. The greater proportion remains dissolved in the water in the form of gas
and serves as an important nutrient for plants. Therefore, CO
2
has two benefits: it reduces the
level of pH in the aquarium, which is usually too high, to a level appropriate for fish and plants
whilst at the same time providing plants with their main source of nutrients. Thus luxuriant plant
growth and lively, healthy fish are guaranteed.
How much CO
2
is needed to maintain a particular pH value depends on the KH in the aquarium.
The higher the KH, the more CO
2
is required. Once the KH and pH values are known, the CO
2
content can be calculated. The following table saves you making the calculations and also
shows the pH values which you can set as an optimum value without any risk to your fish.
CO
2
content depending on pH value and KH
Too much CO
2
auto pH curve
CO
2
correct
Too little CO
2
The auto pH curve shows the levels for the
m
503 and
m
2003 CO
2
kits which the pH computer
automatically maintains when the “auto pH“ option is activated. For your fish’s’ safety, we recom
-
mend having this option activated.
12.2
The correct amount of CO
2
and the correct pH value
JBL recommends a CO
2
content of between 15 and 30 mg/l in aquarium water. This range is
marked with “CO
2
correct “ in the table above. 20 – 25 mg/l have proved to be ideal. This level is
not harmful to fish whilst at the same time promoting luxuriant plant growth.
•
Measure the KH of your aquarium water with the enclosed JBL KH test kit.
•
In the section “CO
2
correct“, look for the pH value which is correct for the KH and the de-
sired CO
2
value.
•
Gradually adjust the CO
2
bubble count so that this pH level is attained.
CO
2
(mg/l)
KH
pH
2
4
6
8
10
12
14
16
18
20
7,8
1
2
3
4
5
6
7
9
9
10
7,6
2
3
5
6
8
9
11
12
14
15
7,4
2
5
7
10
12
14
17
19
21
24
7,3
3
6
9
12
15
18
21
24
27
30
7,2
4
8
11
15
19
23
27
30
34
38
7,1
5
10
14
19
24
29
33
38
43
48
7
6
12
18
24
30
36
42
48
54
60
6,9
8
15
23
30
38
45
53
60
68
76
6,8
10
19
29
38
48
57
67
76
86
95
6,7
12
24
36
48
60
72
84
96
108
120
6,6
15
30
45
60
75
90
105
121
136
151
6,4
24
48
72
96
119
143
167
191
215
239
6,2
38
76
114
151
189
227
265
303
341
379
