Kalk will only dissolve to a certain point given the amount of freshwater available. This is how a kalk reactor works, and why in the reactor you just dump a bunch in, and it dissolves more as needed. Its a good practice to cover your kalk water container as much as possible to extend the life of it. I have been told also, that you do not want to mix more than 5 days worth of kalk water at a time, as it can go bad beyond that time line. I found shortly after deciding to top off with kalk water, that it was too much of pain will all the mixing, and stirring, and rinsing, and making new batches etc, that i got a kalk reactor. Even going with a GEO, it wasn't very expensive, comparing to that of a calcium reactor, or other high end equipment. It really makes things a lot simpler.
Also, its important to know that you need to draw water from your kalk reservoir from a couple inches off the bottom, and not allow it to pull from the very bottom. A slurry of undissolved kalk will collect there, and can cause major spikes if sucked up and added to your tank. You can simply build a small egg crate stand if need be.
