3rd prerequisite Carbon dioxide as a source of sugar – an essential source of energy
Carbon dioxide is produced when all organisms breathe and is used by plants in combination with water and light as a nutrient source for synthesising sugar. It is therefore vital in order for aquatic plants to grow. However, all aquariums essentially have their own unique CO2 requirements. For instance, well-planted tanks with fast-growing plants need more CO2. In order for organisms to thrive sustainably in an aquarium, the long-term CO2 concentration must be between 5 and 15 mg/ml.