It's not so much a recommendation, but there is nothing wrong with doing it. A kalk drip of any type is a good idea. A kalk reactor just takes much of the manual effort out of it.
depends what type of top off system you have. IF its anything orther than drip, where something could malfunction and dump multiple gallons of kalwater into your tank, i wouldnt do it.
Basically it's a 20 gal Sterlite tub and a Pulsafeeder diaphram dosing pump. I fill the tub with RO/DI water, add a couple tablespoons of kalkwasser, stir it a bit and I'm done. I have the dosing pump set to come on at midnight and stop at noon. For full details, head over to http://www.liquidreef.com/ , click on the Equipment menu link, and then scroll down to Calcium/Alkalinity Supplementation, item #4. There's also more pics there as well on how I did it.