When you first set up the tank you should be planting it heavily, with an emphasis on fast growing plants, like stem plants. You want those to grow fast, so you need to be feeding them right from the start. It is also best to assume that Eco Complete is an inert substrate, not a fertile one, so don't try to rely on the nutrients in the substrate. If you use the EI method of fertilizing, a good idea for a beginner, and not a bad idea for anyone, you would probably dose about half of the recommended amounts until the plants build up some more plant tissue mass, then go to the full amounts. Fertilizing isn't, or at least doesn't need to be an exact science. You can over dose quite a bit before there is any risk of bad results.