Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
Yes, you will need to add carbonates to the water.
Nitrifying bacteria use the carbon from carbonates. They will not thrive in water with zero carbonates.
Some plants can use carbonates as a source of carbon.
Carbonates are one of the most common buffers of pH in the aquarium. Especially if you are adding CO2, having some carbonates in the water will help stabilize the pH. Varying pH is not the horror that it used to be thought. Still, a stable pH, cycling around the same values is one indicator that things are going well in the tank.