Within WWW, books or aquaristic shops you will find lots of information about Balling-method with DIFFERENT concentrations and even different salts to use! This is generating some confusion especially for users new to this method.
The good thing: You can use this method very flexible and with several degrees of freedom.
You have the choice!
Recipes increasing Mg-concentration with only one, or two Balling salts. Recommended is the recipe with MgCl2 only, due to not building up depots of Sulfates.
with or without special salt, free of NaCl. This special salt, if used, supports your tank water with additional trace elements/salt than NaCl. Especially in tanks where water changes are done not regularly and no separate trace element mixtures are added, this is a good option. If this option is chosen, Aqua-Calculator calculates your dosage of NaCl free salts in a way that it is like natural sea water (70% NaCl and 30% other salts NaCl free Salt). If you do regular water changes with high quality salt mixtures, trace elements will be added. In this case you do not need add NaCl free salt.
With or without dosing trace element mixtures separately? This is more or less a matter of thought! A separate supply with trace elements might show advantages only in tanks with lots of SPS. Be careful! Adding to much trace elements can also be harmful to your corals, especially because there actually is no test kits available to measure this concentrations as already mentioned also good salt mixtures have this trace elements added. An advantage for regular water changes instead adding trace elements separately is, that there is no risk of overdosing of the trace elements.
Dose trace elements together with Balling standard solutions? This will couple dosing of trace elements to dosing of Ca/Alk/Mg and will thus be pretty easy to use. You have to take care that not each trace element solution can be added to each of the standard balling solutions. I recommend to strictly follow the recommendations of the manufacturer of the trace elements.
Balling or Balling Light ? Balling Light is a newer Advice from Claude Schumacher Fauna Marin. This recipe uses three somehow pimped Balling salts which are available under the Label Fauna Marin. It is said that they have also bio active components and a pH-Buffer). Also three different Fauna Marin trace element solutions are mixed into the standard (liquid) solutions. Balling Light does not use the NaCl free salt mixture, but recommends regularly water changes of 5-10%.
Standard solutions are to be mixed that the maximum solubility of the resp. Balling salt is not exceeded. Within the borders of solubility, it can be lower or higher concentrated. (AquaCalculator has a Standard recipe built in, but can also calculate flexible with different concentrated standard solutions) However your choose your concentration, AquaCalculator tells you exactly which amount you have to dose to achieve the raise of Ca/Alk/Mg you need for your tank.