Corosex is a highly reactive magnesium oxide, specially processed to treat a low pH by neutralizing the free carbon dioxide in water therefore render it less corrosive . Corosex will slowly dissolve and will need to be replenished from time to time. To be used in continuous flow systems.
 

Under certain hardness conditions, pH correction can cause hardness minerals to precipitate out of solution, resulting in cementing or solidification of the Corosex mineral bed. Upflow service is generally recommended with hardness exceeding five grains per gallon. (Always use an in-line filter ahead of an upflow system to prevent plugging of the lower distribution screen.)

As Corosex's magnesium oxide neutralizes the water, it will increase hardness and a softener may become necessary after the neutralizing filter. Corosex can be effectively combined with  Calcite to combine the high flow neutralization properties of Corosex, along with the slower reacting low flow properties of Calcite, reducing potentially high basic properties due to overcorrection.

Calcite is the most common form of naturally occurring calcium carbonate (white marble) which is crushed and screened. It is used to neutralise acidic water. Depending on pH and other parameters Calcite will be exhausted after some time and needs to be replenished.