I made a similar soil to BuildaSoil and have completed 5 back-to-back water only grows with only a top dressing between each grow. I am thinking of dumping my boxes in my outside garden and making new after this grow gets chopped. I am curious to see the insides of my 15-gallon SIPS!
None. Organic fertilizers are often slow releasers of the nutrients and need to ferment or compost for a while to get the nutrients to a level that is beneficial for the plant. At the same time the soil gets balanced and homogenized and a rhizosphere forms.