A 55 gallon tank will take 2-3 bubbles per second, if not more, to maintain a good CO2 level in the tank. It depends on the diffuser/reactor you use, how much surface ripple you use, what filtration method you use, and how heavily planted the tank is. The power filter may cause considerable loss of CO2 if the "waterfall" splashes very much. You don't have to change lights though - CO2 helps the plant growth with any level of lighting.
Speaking of plants, looking at your tank you have two non-aquatic plants in it, that I can see. One is the white edged plant you just added, and the other is the Spathiphyllum.