It's funny actually. I know my plants will need nutrients and how the Grobo is supposed to work. I know you get your first set of nutrients with the Grobo, cool. I read somewhere where someone had said they were running out of #4, make sure to have extra #4, SO... I bought an extra bottle of Macro when I bought my Grobo! Now I realize that every plant has it's own needs, just how important each bottle is, and it's a good idea to have back ups of ALL of your nutrient bottles! ;)