Water taken directly from the tap may contain harmful compounds, which we can easily eliminate by installing an RO filter in the shower or sink, effectively separating impurities from chemically pure water. An osmotic filter for an aquarium, whose final product is RO water, removes both mechanical impurities and those invisible to the naked eye, such as chemical compounds like chlorine. This element is an inseparable component of tap water, responsible for disinfection. The purpose of the RO filter is to protect fish and aquatic plants from its harmful effects. Using cartridges is necessary for the RO filter for the aquarium, and it is important to remember to replace them. If we are the owners of a marine aquarium, the device must be equipped with demineralizing resin, which will additionally remove silicates and carbon dioxide from the water. A marine aquarium is considered much more demanding than a freshwater one, which is why it is so important to always use water from the RO filter for water changes.