Magnesium dropping fast.

[$hing$hong]

Now my tank is currently 7 months old with only frags of zoanthid, ricordea and anacropora.
The problem is the magnesium was stable for the past 6 months at 1290ppm then this month it suddenly dropped to 1140ppm (Also with addition of GHA growth and dying chaetomorpha, not sure if its related to my Mg problem).
I only dose PartB (Baking Soda) to maintain the alkalinity and didnt dose any PartA(Calcium Chloride) due to no measurable Ca intake. I do not run any reactors (no activated carbon/GFO/zeolite). I only do 5% water change monthly due to limited space and location of the tank.

The question is how do I dose Mg back up? Is it better to raise Magnesium by Magnesium Chloride alone or Magnesium Chloride + Magnesium Sulfate mixture?

Parameters:
Salinity: 34ppt /1.025sg
pH:8.2
kh :7.3 dkh
Ca: 420ppm
Mg:1140ppm
NO3: 6.8ppm
PO4: 0.03ppm

Thankyou in advance for any inputs, this is my first time dosing 2-parts so any advice is welcome.

 

[Randy Holmes-Farley]

The observation is either test error or a salinity drop. Magnesium never drops faster than about 1/10th of the calcium consumption.

I suggest not even measuring it:

Just say NO to magnesium testing: RMM is born

OK, this thread has been many years in the making, and I'm posting it here since folks in the chem forum are probably already tired of all the threads relating to problematic magnesium testing. I'm going to propose a method, let's call it the Randy Magnesium Method, or RMM for short. All good...

www.reef2reef.com

 

[$hing$hong]

The observation is either test error or a salinity drop. Magnesium never drops faster than about 1/10th of the calcium consumption.

I suggest not even measuring it:

Just say NO to magnesium testing: RMM is born

OK, this thread has been many years in the making, and I'm posting it here since folks in the chem forum are probably already tired of all the threads relating to problematic magnesium testing. I'm going to propose a method, let's call it the Randy Magnesium Method, or RMM for short. All good...

www.reef2reef.com

Thankyou Randy, the thread you posted gave me a peace of mind by ignoring the test kit (for now).

Also nice to see you are still active in the hobby, I remember seeing you in Reefcentral 14-15 years ago when I was in the hobby.