Hikari RIO+ NO2/NO3 Minus Pad (Gray) is a specialized chemical and mechanical filtration media specifically formulated to reduce nitrite (NO2) and nitrate (NO3) levels in marine, reef, and freshwater aquariums. Designed to trap particulate waste while actively reducing excess nitrogen compounds from the water column, it helps create the conditions required for improved water quality, reduced nuisance algae growth, and overall aquarium system stability. By reducing nitrite and nitrate before they can negatively impact fish health and water quality, it helps support balanced aquarium ecosystems and long-term aquatic health. Easy to cut, install, and replace, and precisely manufactured for consistent results, Hikari® RIO+ NO2/NO3 Minus Pad (Gray) helps maintain a stable aquatic environment where fish, corals, and other aquarium inhabitants can thrive.