Mr31415
New Member
Should I be dosing Mg? I am asking because after reading this thread: https://www.reef2reef.com/threads/just-say-no-to-magnesium-testing-rmm-is-born.1017528/ I had some conflicting data to deal with.
My setup: 91g Red Sea Reefer 350 G2+, 3 months old, mixed reef. I have 2 SPS, 2 tiny LPS, some softies, 3 fish. I do a 24% water change once every 2 weeks with Red Sea salt (not the Coral Pro). RO/DI water measures 1ppm at most. I dose 500ml kalkwasser via red sea dosing pump daily, 7ml Red Sea part A (alk) daily and 3ml Red Sea part B (Ca) daily. In my sump I have a ball of chaeto on reverse photoperiod. I have almost no coralline growth yet - just one or two tiny spots.
My parameters are relatively stable. 25.2C, 8.1pH, Ca is 420 - 430ppm, Alk is 8.2 - 8.6 dKH, salinity is 35.0 PSU.
The problem is that my Mg is testing high. I have been testing it via both Salifert and Hanna test kits many times. For the past month it seems my Mg has been climbing - that makes no sense as I am not adding Mg to the tank.
So yesterday I made new saltwater for my water change, at 35.0PSU as per my calibrated Hanna HI98194. I measured the tank just before the water change, it was also at 35.0PSU.
Tank: 35.0 PSU, 8.2 dKH, 418 ppm Ca, 1435 ppm Mg. (All except salinity was with Hanna HI97115C).
New water (Red Sea Salt): 35.0 PSU, 8.4 dKH, 422 ppm Ca, 1475 ppm Mg. I then remeasured Mg and got 1500 ppm Mg.
I was expecting closer to: 35.0 PSU, 8.2 dKH, 430ppm Ca, 1310 ppm Mg as per Red Sea.
According to Hanna, the measurements have an error of 5% of reading, so 1475 could be 1400 - 1550. Therefore 1475 and 1500 are within the margin of error. However it is still at best 100 ppm higher than what I would expect at 1310 according to Red Sea.
I tested using Salifert and here are the strangest results:
Tank: 1425 ppm
New water: 1375 ppm
Even though new water is closer to the advertised value, they are swopped - Salifert says tank is higher than new salt, and Hanna says opposite. I can only presume the margin of error on the Salifert is even worse than the Hanna.
PS: All test kits are fresh and very far from expiry, both very new.
Here is my question: Considering Randy's recommendation to not measure Mg but dose based on ratios, I should be dosing 5% or so of Red Sea Mg relative to Ca, so 0.15ml Red Sea Part C (Mg) daily. However all my measurements are in conflict with this as they all are way above 1400ppm. So should I dose and ignore the test kits? Or not dose?
See my testing below. Vertical blue lines indicate water changes. Red lines are manual dosings before I got the dosing pump.
My setup: 91g Red Sea Reefer 350 G2+, 3 months old, mixed reef. I have 2 SPS, 2 tiny LPS, some softies, 3 fish. I do a 24% water change once every 2 weeks with Red Sea salt (not the Coral Pro). RO/DI water measures 1ppm at most. I dose 500ml kalkwasser via red sea dosing pump daily, 7ml Red Sea part A (alk) daily and 3ml Red Sea part B (Ca) daily. In my sump I have a ball of chaeto on reverse photoperiod. I have almost no coralline growth yet - just one or two tiny spots.
My parameters are relatively stable. 25.2C, 8.1pH, Ca is 420 - 430ppm, Alk is 8.2 - 8.6 dKH, salinity is 35.0 PSU.
The problem is that my Mg is testing high. I have been testing it via both Salifert and Hanna test kits many times. For the past month it seems my Mg has been climbing - that makes no sense as I am not adding Mg to the tank.
So yesterday I made new saltwater for my water change, at 35.0PSU as per my calibrated Hanna HI98194. I measured the tank just before the water change, it was also at 35.0PSU.
Tank: 35.0 PSU, 8.2 dKH, 418 ppm Ca, 1435 ppm Mg. (All except salinity was with Hanna HI97115C).
New water (Red Sea Salt): 35.0 PSU, 8.4 dKH, 422 ppm Ca, 1475 ppm Mg. I then remeasured Mg and got 1500 ppm Mg.
I was expecting closer to: 35.0 PSU, 8.2 dKH, 430ppm Ca, 1310 ppm Mg as per Red Sea.
According to Hanna, the measurements have an error of 5% of reading, so 1475 could be 1400 - 1550. Therefore 1475 and 1500 are within the margin of error. However it is still at best 100 ppm higher than what I would expect at 1310 according to Red Sea.
I tested using Salifert and here are the strangest results:
Tank: 1425 ppm
New water: 1375 ppm
Even though new water is closer to the advertised value, they are swopped - Salifert says tank is higher than new salt, and Hanna says opposite. I can only presume the margin of error on the Salifert is even worse than the Hanna.
PS: All test kits are fresh and very far from expiry, both very new.
Here is my question: Considering Randy's recommendation to not measure Mg but dose based on ratios, I should be dosing 5% or so of Red Sea Mg relative to Ca, so 0.15ml Red Sea Part C (Mg) daily. However all my measurements are in conflict with this as they all are way above 1400ppm. So should I dose and ignore the test kits? Or not dose?
See my testing below. Vertical blue lines indicate water changes. Red lines are manual dosings before I got the dosing pump.
