Is this what you are talking about:
Plantex CSM has no Boron in it, so it must either be added, or purchased from a supplier who pre-mixes Plantex CSM+B. To add Boron to Plantex CSM, add 10.5 teaspoons of Plantex CSM plus 1 teaspoon of Boric Acid.
To make your dosing solution, mix in 1/2 litre of water:
1 tablespoon of Plantex CSM+B and
1 tablespoon of Magnesium Sulfate in 1/2 litre of water.
A 1/2 liter of Plantex CSM Dosing Solution is a lot of solution for the typical aquarium, so you may wish to experiment by reducing the quantities to make a smaller batch. To reduce, you may wish to try 1 teaspoon of Plantex CSM+B and 1/6th liter of water (167 milliliters).
Many people recommend refrigerating your micro-nutrient solutions. Commercial products usually contain a Chloramine or Chloride as a preservative,