For several months since I started my hex I have had problems with low alk and high calcium readings (alk 2 meq/L and Calcium over 600!). I think this was from using DIY rock and natural sea water. For the last couple months I slowly dosed Seachem Reef Builder through an IV mixed with my evap water to raise carbonate alkalinity. I started with 3 teaspoons / gallon. Steadily increasing the dosage per gallon to 6 teaspoons currently. I finally got it in a good range. [smiley=beer.gif] Check out my results below: 8) 8) 8) If you have a similar problem, I hope this helps!