Just kalk in big tanks!

[REEF SMAC]

So would it be the best of both worlds to employ one each calc and kalk reactors, calc day and kalk night?

I don't know about it being the "best of both worlds". One or the other will work just fine up to a point. Kalk alone will work just fine for a system where the demand is equal to the evaporation rate. You can even push that a little by adding vinegar to the kalk as mentioned.
Eventually you might get to the point that Gig is experiencing it sounds like, where you have to start dosing two part or use a CaRx to keep up.

The "other world" is you run a CaRx on your system and when your demand gets high enough you run the flow and bubble rate so high that your PH starts to run really low all the time.(or maybe you can keep buying bigger Rxs) Then you add kalk to raise the PH back up and help with the demand too.

If kalk alone keeps up with your system demand it's a great way to go. IMO.

It just seems to get to a point when your demand is high enough that adding that much kalk and vinegar seems to be a little much.
Makes me nervous anyway.

How much vinegar would you guys add to 5 gallons of saturated kalk anyway?
Are you putting in 4 gallons of kalk and a gallon of vinegar everyday?

 

[sanddollar789]

We use a 6 inch thick sand bed in our sump and occasional kalk (maybe 4 times a year) in top off water when the mood strikes. My husband is not a fan of dosing and strives to make his tank as self sustainable as he can. Our SPS grow "uncontrollably" and we regularly trim them back. He says when the sand is thick enough anaerobic bacteria grow and break down the sand and release the calcium naturally into the water. In addition to the thick sand bed the sump is loaded down with extra pieces of live rock and even some clippings from the main systems corals.