Thanks! Just a question as I am a nooby but why wood I not need Calcium and Magnesium?For that size tank to start with you would need
Accurate salinity measurement
Alkalinity
Nitrate
Phosphate.
Salifert test kits are all you need.
With your planned waterchanges you do not need Calcium or Magnesium Kits especially if you use a product such ad AFR to maintain Alkalinity.