Hi RobA-
It would be best to install an aeration system from the beginning and not to wait until it is needed. By then it could be too late. When aeration is needed most is at night and durring still, cloudy days when there is no sunlight for photosynthesis to produce oxygen. Durring this time the oxygen demand is still present leading to an oxygen depletion. If it is possible, the most dependable type of aeration is electric. The cost of a complete electric aeration system for your pond can range between $1200 and $2000 depending on the layout of your pond and number of diffuser locations (one or two).
