This is the most sophisticated solar air pump in the pondxpert solar range as it has the benefit of battery back up. When instant oxygen is not required simply switch the unit to back up and it will charge up the rechargeable batteries supplied inside the unit. This stored energy can then be used to supply oxygen to your pond when desired.air pumps are essential for the health of your fish especially in the summer when oxygen levels are depleted. Additional air leads to additional water circulation and a healthier pond.the pondxpert solarair 200 plus is perfectly suited for the following ponds br • no fish 1,500 litres 330 gallons br • fish 1,100 litres 240 gallons br • koi 500 litres 110 gallonsaccessories included with the solarair 200 plus br • 2 x 4mm air line 2m br • 2 x 20mm air stonesolar powered the solarair air pumps are powered by the sun and contribute a good flow of air into the pond. No electrical installation required!battery included excess energy generated will be directed to power up the lithium battery inside the unit. a 6.3v adaptor can be used to charge the battery from the mains.