If your planning on using something like general hydro flora series. In aero you will want to go by the mixing ratio thats right on the bottle but never full stregth. when your plants are young keep ppm very low in aero they can burn quick fastest nutrient uptake. When young in veg keep ppm around 300 or 400 and never over 500. Then veg them to your liking and keep on veg nutes through first week of flower. Remind you to get a loww ppm you will never use full stregth. Start off with 1/4 stregth of what the bottle reccomends if your ppms go above 500 dilute it down to 300 400. Adjust ph as neccesary 5.7 to 6.1 is where i like mine. After first week of flower go with half stregth bloom feed. Then your next nute change after your first bloom feed on the bottle the plants can handle higher ppms at this point you can play a little with nutrient strength but you have to keep an eye on the plants read them. Anything over 1000 ppm in aero is a hot load. Playing with fire some strains can handle lots of food some will burn to a crisp. And your plants will drink water and food you have to watch ph and ppm to see if there drinking the water or eating the food. Allways replenish with water between nutrient changeouts.