Indications of nitrate deficiency include an overall yellowing of the plant, particularly in the older leaves and progressively smaller new leaves or stunted growth. some plant species take on a reddish tint. When there is a nitrate deficiency in the aquarium, green filamentous algae, fuzz algae, and hair algae become frequent.
Nitrate concentrations of 3.0 to 10.0 ppm are recommended in a planted aquarium.