Recipe for 4dKH solution for the indicator:
1. Measure 3000 ml, or 2000 ml, or 1000 ml of distilled water or from the RO filter
2. Weigh 3.60 grams of NaHCO3 baking soda, add to 3000ml of water
or 2.40 grams of NaHCO3 to 2000ml or
1.20 grams of NaHCO3 to 1000ml, etc. of water and mix thoroughly,
this will give a standard solution with a hardness of 40 dKH
3. To 450 ml of distilled water or from the RO filter, pour 50 ml of 40 dKH water from point 2 and mix well, and it will give you 500ml of water with a hardness of 4dKH
Pour the prepared solution into the indicator tinting with a pH test (3-4 drops per 5ml of indicator) and then it would be done.
blue: not enough
green: good
yellow: too much
If you have strong light, 0.5W / L and more, it’s better to keep it in a yellow-green color and also maintain good circulation of water in the tank.
The indicator should be installed away from the CO2 source in the tank at a height of about 1/4 to 1/3 of the tank height from above.