JBL FlorapolFeatures: Long term supply for the substate: long term substrate fertiliser for freshwater aquariums. Nutrient depot: contains all important plant nutrients such as iron and clay, stores nutrients and releases them as required. Optimal promotion of plant growth means less algae growth. No phosphates and nitrates. Use when setting up a new aquarium: mix nutrient substrate concentrate with substrate, cover with a layer of washed gravel sand.