I grow in Earthboxes ( 65-75 quarts of mix) and typically use organic, such as TomatoTone. I lay down 3 cups of the TomatoTone in a strip, bury it by 3 to 4 inches of potting mix and good to go. 2 cups of dolomite lime is mixed in to all the growing medium for each box previously. I supplement with about a teaspoon of Calcium Nitrate in the watering tube every week primarily to prevent BER (Blossom end rot) I have a VERY long growing season and I will usually add some liquid ferts like seaweed later in the season, also in the tube. The idea behine a SWC is that it is a "closed sytem" meaning, unlike a regular container, the ferts do not wash out with rain or overhead watering. Generally you are adding everything the plants need at planting time. Organic ferts will in fact work in a soiless growing medium, although I would agree they break down best in the ground or in dirt. I use them primarily to avoid salt build up associated with chemical ferts as I reuse my growing medium year after year. Linda