I just started my first planted tank. 30G fresh water. I have T5 10000K 42W lighting. No CO2.
I have Cobomba caroliniana, hairgrass belem, Helanthium tenellum, Vesuvius and some Fissidians and Flame moss.
If that is T5HO lighting, that is a lot of light to not be dosing and not injecting CO2 (I would reduce the lighting until you get CO2 and fertilization).
1. If we do a mix of micro and macro every other day.. That's dosing everyday. Is that really necessary? Can plants really use up all the nutrients in a day?
In a high light aquarium, plants can use up nutrients very quickly. The dosing regime you have posted appears to be EI, and the goal of EI is to achieve a stable level of (excess) nutrients so that they are always available to plants.
2. Also, does it require 50% PWC? Some say 25%, some 50%.. Any points on that?
Classic EI requires 50% water changes in order to keep the levels of nutrients down.
3. I am planning to use Flourish Excel. Is this good enough for carbon to live without CO2?
In a high light aquarium, CO2 is much better. Excel is more suited for low/medium light aquariums where the carbon requirements of plants are less.
In addition, Excel can become quite costly in the long run.