IX1HPNanswered grow question 2d ago If you use pre-fertilized substrates like All Mix, wait 3 or 4 weeks - If you use lightly pre-fertilized substrates like Biobizz Light Mix or Atami Janeco (and all other lightly fertilized ones), wait two weeks. A friend's advice: even if they are organic fertilizers, always start with 25-50% of what the Biobizz charts suggest (but this rule applies to all types of fertilizers). You can always add more fertilizer later, but taking it away is difficult and can cause some problems. If you need more info, feel free to message me. Happy growing!