Pour salts in bottles: Part A: Calcium Nitrate Potassium Nitrate Iron DTPA (10 or 11%) Part B: Monopotassium Phosphate Magnesium Sulfate Manganese Sulfate Sodium Borate Zinc Sulfate Sodium Molybdate Fill the rest of the bottles with RO/distilled water. Potassium Hydroxide flakes if you need pH up. (caution, poison! clean hands after using, bad for eyes) Nitric acid, phosphoric acid, or sulfuric acid for pH down. (bad for eyes! don't drink. Don't pour in eyes or hands. Wash hands after handling.) Get HydroBuddy: First pick the substances you're using by hitting the "Substance Selection" button. Next, pick a built in formulation so you have a good base recipe to work with. I picked a recipe from University of Florida. (keep things simple for now) Set "Stock Solution Volume" to 1, check the "liters" radio button, Solution preparation type A+B, and concentration factor 400. Keep the calculation type as "input desired concentrations". Set the ppm of Cu to 0 since we're not using a substance to provide Cu. Finally, click "Carry out calculation" Now click the results tab and it will show you how much of each salt to put in each 1 liter bottle. Now these stock solutions can be used in a 1:1 ratio, 10mL of each for every 1 gallon of final reservoir solution. It has an NPK ratio of 1: 0.74: 1.44. Label the bottles with how much of each salt you put in it so you can remake the bottles without hydrobuddy next time.