Pond Logic PondAir Systems are an excellent choice for use in Koi ponds. These quality units feature highly efficient diaphragm compressors which cost as little as 17¢ a month to operate. Adjustable air flow regulator lets you fine tune your aeration with the turn of a dial. 2" round air stones diffuse beneficial oxygen into your water garden or decorative pond. Pond Logic PondAir Aeration Systems are ideal for decorative ponds and water gardens up to 2,000 gallons. Powered by highly efficient diaphragm compressors, Pond Logic PondAir Aeration Systems infuse your pond with valuable oxygen while remaining whisper-quiet and cost effective. An airflow control valve on the top of the Pond Logic PondAir Aeration System lets you adjust the aeration output to your pond with the simple turn of a dial. Every Pond Logic PondAir Aeration System includes 2" round air stones and flexible black vinyl air tubing.