Regular water changes also replenish other elements, such as dissolved minerals (calcium, magnesium) and carbonate salts in the water, and are a necessity for fish.
Plants use nutrients continuously just like CO2, and a regular serving of liquid fertilizer will benefit most tanks. Dosing can be done daily, though every few days or once a week will also suffice. Due to evaporation of water, some elements of fertilizer not used can build up over time, so regular moderate water changes (20 to 40 percent weekly or every other week) are advised when using fertilizers to prevent any dangerous nutrient accumulation. Regular water changes also replenish other elements, such as dissolved minerals (calcium, magnesium) and carbonate salts in the water, and are a necessity for fish.