Cause they dont. Once your Sps demand reaches a certain point the kalk never keeps up. Ask anyone with a fully stocked tank if they use only kalk and they always wind up using a reactor.
Ask me I fit the profile of anyone with a fully stocked sps tank , I doubt there are many tanks as heavily stocked with growing sps.
I don't make this stuff up.
Do you use a CaCO3 reactor? Have you tried limewater? Or are you simply repeating what you may heve read somewhere?I'm guessing you use two part via the bubble magnus dosing pump noted in your signature.
I think kalk limitations are overstated, and Ca CO3 Reactor limitations are understated . Some folks don't actually maximize the kalk dose over the course of the day ;often precipitation takes a toll with less than optimal dosing. Others just like to echo things without seeing for themselves and somehow they become common truisms which aren't completely true.
Like Dan, I used a Ca CO3 recator for years and had problems with alk consistency and ph even when dosing kalk with it and becme concerned about what was in the media being dissolving; not just PO4 but every substance including toxins the coral that made it may have stashed in it's bones. Keeping up with all the equipment , CO2 bottle, CO2 regulator, bubble flow, circulating pump, dosing pump,etc.was a pain and control over the actual dose was indirect at best. My calcium reactor works best for my system where it has been placed for the last3.5 years ,on the storage shelf.