There doesn't seem to be much advice on where to place an airstone. I have read that placing an airstone directly on the bottom of a pond is harmful to a pond. This is because the air diffuser (airstone) creates turbulence at the bottom of the pond which lifts and stirs sediment through a pond.

Many air diffuser systems have a plate which the diffuser is attached to which prevents contact with the bottom of the pond. If it is truly harmful to place an airstone/diffuser directly on the bottom of a pond, it seems that many pond owners make this mistake. Any opinions???