mr. james ur thinking of kalk drip he's asking about a reactor
basicaly a reactor it used as a top off system. there is a reaction chamber that has a lot of kalk in it and has some type of stirring mechanism that stirs the contents a few times a day keeping the water in the the chamber highly saturated, the most common way to use the saturated contents of the chamber is to have some type of auto top off system on the tank and a small pump is used to pump fresh water through the reactor pushing out saturated kalk water into the tank
the principle is that water can only take some much kalk before it cant mix any more so the un-mixed portion of the kalk sits in the bottom untill new fresh water enters the reactor and stirs, when using a sealed reactor the kalk never goes bad being that it is never introduced to air. but most people completely clean the reactor every 1-3 months
the problem with a kalk drip is that the mixture of kalk and water is sitting exposed the air and will basicaly go "bad" with in 7 days
just another way to make life easier, i personaly have no hands on experience with a kalk reactor but know a few that do., i have researched some becuase i plan and building one soon just need to find some acrylic tube