This this solar powered air pump oxygenates pond water in sunny weather when oxygen levels are depleted. Two separate air stones, each with a metre and a half of tubing, allow you to provide oxygen to your entire pond rather than just one section. It is solar powered so that you will save money from your energy bill and you won't have to run a mains cable outside. This product also comes with a battery back-up, which allows the pump to continue working even during cloudy spells Primrose Solar Powered Pond Oxygenator Aerator 2 Stone Battery Backup 120LPH