MixAir Ornamental OB1 Weighted Pond Diffuser Aerator Air StoneUse the MixAir Ornamental OB1 for small backyard ponds, odd shaped alcoves in ponds or in small tanks. Fill the built in ballast completely with pea gravel before placing it where you want to improve your water. The Ornamental OB1 is a fine bubble diffuser that both aerates and mixes in one efficient device. It is designed to generate dissolved oxygen throughout a water column to accelerate inversion or turnover which keeps water fresh. The OB1 works