I am contemplating using kalkwasser in my mixed reef which is a Fiji "cube" 57g with 20g sump. This is my second tank; I also have a 20g mixed reef which is 2 years old. The new tank is 8 months old and I have been dosing Brightwell alkalin 8.3 (6ml/day) to maintain alkalinity and pH for a few months now. I am using a single BRS 2 part dosing peristaltic pump attached to my Hydros system which slowly drips the Brightwell alkalin 8.3 about 8x per night to combat the nightly pH drop and maintain steady alkalinity levels. This method has worked well and I have maintained alkalinity of 8.5dKh and daily pH between 8.03 - 8.13 but my tank is starting to use more calcium as I have some LPS and recently ventured into SPS corals. I purchased the ATI essentials 2 part to try it out. Two months ago ago, before adding the SPS, my calcium was at 350 and magnesium 1350. I used the ATI part 2 solution to raise calcium to 400 which brought magnesium up to 1380. 20ml of part 2 raised calcium 25ppm and magnesium 15ppm. I did not dose ATI part 1 (alkalinity) as I have been using the Brightwell Alkalin 8.3 instead, so for the meantime I was just using the ATI part 2 to try and get calcium up. Wondering if I should keep using the ATI part 2 to get calcium up around 450 but this will also bring magnesium up to 1410 (which is marginally high depending who you ask). With the calcium depleting faster than the magnesium, these levels are sure to get out of balance over time. I guess this is the problem with 2 part dosing. Hence considering kalkwasser. Water changes have been minimal for the first 8 months of this reef as I had low nitrate and phosphate resulting in dinos at first. But the dinos are under control and nitrate and phosphate look good at 3ppm nitrate and .03 phosphate. So pretty soon I will be doing more water changes which will help with the low calcium. Using Fritz RPM salt. Not sure which direction to go. Looking for advise. TIA.