Found in runoff from agriculture, animal yards, etc., these toxic substances contribute to over-nitrification and algae growth. High quantities of nitrates in untreated water can negatively affect the later stages of flowering, when cultivators typically try to limit nitrate levels in the growing medium. A reverse osmosis system will remove 95%+ of nitrates present in the feed water, giving hydroponic growers a consistent base from which they can control their nitrate levels during fertigation.