What type of substrate is best for the planted aquarium? How deep should it be?
While there is no absolute answer to this question, substrates that are porous and have an average size of 2-3 mm. will work best. If the substrate is too fine, there is a risk that it will pack down too tightly and create dead areas. If the substrate is too coarse, small areas will develop that trap waste and create pockets of decay. While smooth surface substrate will not allow proper root attachment, a porous surface allows good root attachment and helps to anchor the plant in place. Generally you will want 3 inches of substrate, though this could be terraced to provide different depths in the aquarium. Large plants could even be placed in “flower” pots buried in the substrate. This last method can be used to add plants to an already established aquarium that does not have the proper depth or type of substrate.
