Fish requiring oxygen, plants mainly requiring carbon dioxide (CO2)!
Magnificient and well growing plants are necessary for every beautiful and naturelike aquaria. To get plants looking great and growing well, they need light, nutrients and thereby mainly carbon dioxide (CO2). Without this carbon (C), plants cannot build new cells, they atrophy.
The CO2-requirement of your aquaria depends on many factors, number of fish and plants, light conditions, filtersize and filter medium, just to name the important ones. That is why you should measure the CO2-content of your aquaria (see figure beside). 5-10 mg CO2 per liter water is therefore an ideal value for optimum growing of your aquatic plants. If you should have in your aquaria a lot of aquatic plants under powerfull light conditions, it could be that you need a second CARBONATOR, despite of the high efficiency of the CARBONATOR (no other gases), to reach this CO2-content.
Therefore it should be the CO2-content in the forefront and not a pH-value of 7, which is often described as very worthwile. You just need an unnecessary amount of CO2 to keep the pH-value at 7 (e.g.: if you have a carbonate hardness of 12, you need 40 mg 40 mg CO2 per liter). A pH-value of about 7.5 is also very qualified for most fish and aquatic plants.
CO2-measurement:
The pH-value of water is mainly defined by the quantity of carbon dioxide (CO2) and the carbonate hardness, you are able to evaluate the CO2 quantity by measuring the pH-value and the carbonate hardness. In the graph to the left you can figure out the CO2 level of your water.
The scale starts with 0,5 mg CO2 (gasequilibrium with air), the minimum value you can reach by strong ventilation or surface-movement of the aquarium water. The accessory pH-values for the carbonate hardness can be seen on the horizontal axis. The dotted lines show as examples, how to evaluate the CO2 level corresponding to your measurements. As well, you can define at which pH-value 10mg/l CO2 are soluted in the water. Each aquarium is an individual biological system in which are variations in the CO2 level. In the morning the pH-value is usually lower than in the evening, which is caused by the CO2-consumption of the plants under light conditions.