the holy trinity?

[uberape]

im a beginner and need to ask: when balancing between light ferts and co2 do you not also need to factor in how many plants you have and what type? im trying to grow a carpet and have been trying to out compete algae but im not doing that well. ive added hygrophelia corymbosa which i know grows quickly at least. I also have attached a clipping of ivy to the tank with roots in the water. They are brilliant at consuming nutrients ( i have their roots in a vivarium and the water is crystal clear). any critisisms or help will be much appreciated. its not poison ivy btw.