Wes,
Thanks for remembering.
My best advice is to supercharge that reactor (or upgrade it). When I bought my reactor for the business I bought it with doubling the total volume capacity in mind. So, I am good for up to 750 gallons with this dual chamber CR6.
I purposefully allow my Ca, MG and dkh to deplete over the week by dialing the reactor back a bit (approx 80 bpm and steady slow thin stream of effluent). I am a bad reefer and don't test that often, but I would say that the Ca swings 3-500 ppm and dkh 2 points from 11-9 or so. When i do a water change, I dose up using B-Ionic only - not sure how many milliliters it is, but I use one of those 16oz red cups from Sam's Club - I use more Mg and Alk than calcium - but it eventually works out in the end. I continue to swear by ESV's product - anyone who has seen my tank and prop system will testify to what it's capable of producing - and for me, thats the pudding!
Hope that helps, feel free to drop me a line if you have other questions.
House