Chihiros Doctor has 3 preset modes for plants, fish & shrimps. When used in the plant mode it suppresses algae growth & promotes plant growth. The fish & shrimp modes kills pathogenic bacteria in the water without harming beneficial bacteria or livestock. This is the newest Chihiros Doctor & is the fourth generation rated for tanks larger than 125L(33Gal). The Chihiros Doctor is controlled in the mobile app 'My Chihiros' and is enabled by Bluetooth connection. Note this product can only be used in tanks with TDS below 500ppm.4