There's more to mixing up a nutrient solution than measuring concentrate and dumping it in the water. Your water almost certainly already holds some minerals, so to measure nutrient concentration, you'll need to start by figuring how much dissolved minerals were there to begin with. Use a meter to determine the EC (electrical conductivity) of your water before you add anything. That number tells you the mineral concentration you're starting with.
The ideal mineral concentration for an aeroponic nutrient solution differs according to the plants you're growing. Say lettuce grows best at EC 1.6 but your water is moderately hard with a EC of 0.5. You won't be able to add as much nutrient concentrate before passing the ideal range your lettuce appreciates. Should you push the 1.6 limit? Should you use a water softener? This is where experimenting and experience comes in.
