CO2 fertilizsation in an aquarium has many advantages:Part of the CO2 which dissolves in water forms carbonic acid. This means that CO2 can be used to set the pH value (acid content) of the aquarium water to ideal levels for fish and plants, similarly to those which prevail in nature. Aquarium fish are particularly fond of slightly acidic water. It has a positive effect on their highly sensitive skin. Trace elements which are important for plants and fish are taken in more effectively. Unsightly lime deposits are avoided on plant leaves (biogenic decalcification). Good plant growth = no algae. In aquaria with strong growing aquatic plants, troublesome algae have practically no chance. Nutrients conducive to algae growth, such as phosphates and nitrates, are absorbed immediately by the plants. Plant growth starts to flag when CO2 is lacking, however. Surplus nutrients are no longer consumed quickly enough. This is the chance for algae, as they need only the most minimal amounts of CO2.