Exercise 2: pH - lab of the 26.2.2007

We have measured the pH-value with an indicator, which we mixed up with the aquarium water, which becomes green. This colour we compared with a colour scala and found out that the pH is 8,5.
It would be ideal if the water have an ph-value of 6,5 to 7,5, so in our situation we should mix our water up with CO2.