How Long do you Keep Kalk Powder

[straightrazorguy]

Hi reefers. I run an Aquamedic kalkwasser stirrer to my 55 gal mixed reef tank (plumbed inline with a 35 gal refugium, on a reverse lighting schedule). I started it more than a month ago, and the water in the stirrer still looks nice and milky. I plan on introducing more SPS, and eventually have an SPS dominated tank. For now, I can keep the Ca at acceptable levels, but I have to keep dosing more and more every week.

Is there a limit to the kalk's efficiency? Does one have to change the powder in the stirrer? If so, how often?

[MitchM]

Mixed kalkwasser will absorb the CO2 in the air and make calcium carbonate which is useless to you.
The length of time it takes for this to happen will depend on how tightly sealed you keep your reactor.
I would add enough kalk powder to just keep a thin layer present on the bottom of the reactor and add more powder as needed only.
You shouldn't have to change the powder. It should all get used up.