Bumping up magnesium! Only magnesium?
A test of salt mixes available in EU.
https://reefhub.pl/test-of-marine-salts/
If it is about a new setup for a mixed reef it may not matter much as all commercial salt mixes are good. As cycling a new system and installing diversity needs a lot of nutrients there is no salt mix available on the market which has to much of them. When one has the availability of good tap water this can be used for a new setup. Taking in account what is added by introducing
real " live " rock!
As SPS is the goal probably one wants to see bright and fluorescent colours and is cycling nutrients not part of the setup. A mixed reef with SPS showing natural colours is still a challenge , one may struggle cycling and exporting nutrients in a balanced way. Opt for a very low nutrient system for keeping SPS is a choice. If that option is taken, maybe it is best not to use any so called "life" rock as it will compete with the coral holobiont. Setting up a new aquarium for SPS only, one may consider not to use any "live" rock and use the coral holobiont as a base for introducing the diversity needed with minimal competition certainly when captive cultured corals are used, cultured in other stable conditions as available in nature. They may not be able to compete with natural diversity.
When setting up a VLNS for SPS, based on an effective skimmer, one will end up with an unbalance in the nutrient supply sooner or later if one does not take any precautions , no matter what salt mix is used, as a skimmer constantly removes nutrients and TOC very selective. If a phosphate absorber is used one must be aware it does not only absorb phosphate.
The salt mix used for water changes may be determinative for keeping up the balance and as most if not all commercial salt mixes try to be an imitation of natural seawater this balance will not be restored without intervention.
My opinion, it does not matter what salt mix is used as most commercial salt mixes are of very good quality, as long it is known what is in it.- exactly.
I do not believe in so called " probiotic " salt mixes. If they have an influence on the coral holobiont, the effect is not known! It may as well be "contrabiotic".
We prefer "Colombo", a Dutch brand, because it is low in sulphate. As most SPS keepers do not use any bio-filters it does not matter.
