Basically, ONLY the growth mode is used at first. The flowering mode is SWITCHED ON (not INSTEAD of the growth mode). The ideal light for flowering is when the growth and flowering modes are equally bright. Allowing ONLY the flowering mode to light up would be wrong, as the light is TOO red and there is no UV light. With the GCx-4 and GCx-9, it works like this: For very small plants, it is sufficient to reduce the growth mode to 10% or 20%. As the plants grow larger, the growth mode is gradually increased. Larger plants require more energy. At the end of the growth phase, the growth mode should be set to 100%. At the beginning of the flowering phase, the growth mode is reduced again to 50%. At the same time, the flowering mode is increased to 50%. During the flowering phase, both settings are increased synchronously: growth mode and flowering mode each to 60%, and so on. After ⅔ of the flowering phase at the latest, both mode controls should be set to 100% so that the plant receives the maximum light output. It works similarly for the GCx-16 and GCx-25: basically, the same as for the GCx-4 and GCx-9, but there is only one control and one toggle switch. During the growth phase, the toggle switch must be in position 1. This only controls the growth mode. At the start of the flowering phase, the toggle switch must be switched to position 2 (both parts now light up), and the control should be set back to 50%.