Yes, Amano suggests that some of the ADA liquid fertilizers should be used for the first time after 3-4 weeks from the initial set up. However, one must understand the basic difference between an Amano set up and a set up which is fertilized by liquids only before making this suggestion a general one. An Amano set up is heavily based on substrate fertilizer called Power Sand. This substrate is rich of everything which plant needs. It is so rich of these substances (e.g. NH4) that the first weeks are used only to dilute the overdose in the water column. This is done by frequent water changes and filtering with active carbon. After 3 weeks NH4 drops and you can put in fishes and get rid of the algae from the glasses and remove active carbon from the filter. This is the point you start dosing liquid fertilizers. So it is clear that you cannot follow this regimen when the only source of fertilizers is from liquid additives. If you do not have a rich substrate which needs time to settle, you should start dosing your liquids from the start. That's exactly the same thing that Amano is doing (i.e. fertilizing his plants from the start), his substrate is only more than enough to do the job for the first weeks.