Reverse osmosis (RO) and deionization (DI) are two methods commonly used in the preparation of freshwater for use in a marine aquarium.
Reverse osmosis is a process that involves forcing water through a semi-permeable membrane, which allows water molecules to pass through while blocking impurities such as dissolved salts, minerals, and other contaminants. The result is purified water that is free of impurities, including harmful chemicals that could be detrimental to marine life.
Deionization is a process that uses ion exchange resins to remove dissolved minerals and other charged particles from water. This process involves passing water through a column filled with ion exchange resins, which attract and bind to positively or negatively charged ions in the water. The result is water that is highly purified and free of dissolved salts and other minerals.
When preparing water for a marine aquarium, both RO and DI are typically used together in a two-stage filtration process. The first stage involves the use of an RO unit to remove large impurities, while the second stage uses a DI unit to remove any remaining dissolved minerals and other contaminants. The resulting water is typically very pure and ideal for use in making artificial seawater for a marine aquarium.