First off let me suggest you read Randy's articles in the chemistry forum. Trust me it'll be the best reads of your life. With me saying that, and though I always suggest using a kalk bin instead of a reactor, here's my opinion for your current situation:
- Kent marine Kalk: I would suggest not using them because you can find kalkwasser (Also known as Pickling Lime) at a local store or even order it for a lot cheaper than what marine Brands try to sell to customers. On top of that Pickling Lime is food-grade, meaning it is put through more stringent standards (Purer, safer, etc). A brand I use is "Mrs. Wages" Pickling lime. Most stores carry it, but the season is not in quite yet. Where do you live? Based on your location it'll be easier to find some for you.
Dose of kalkwasser: I am a bit confused on this matter because you plan on using a Kalk Reactor. Water can only be saturated to a point. After that point, pickling lime will simply precipitate out of solution and wait till fresh water comes into the unit to be saturated.
Now if you mean a Kalk Bin, instead of a Kalk Reactor, the usual amount PER GALLON is two tablespoons. That's the highest you can dose (Water will be fully saturated). The real question you'll need to find out about is how much your pH will be affected.. and then we can determine how much vinegar to use in the Kalk bin to control your pH.
The timings of Kalkwasser: I typically have my bin on 24/7. Some people choose to run it only at night to balance their dropping pH as coral activity (photosynthesis-wise) shuts down. On issue with this is that when the timer clicked on you'll end up dumping a lot of Lime water right off the bat, which stresses livestock. So again, I suggest just leaving it on.
HTH
