It’s almost impossible to introduce too much oxygen to your pond, since an overabundance of air will simply escape as bubbles. Actual oxygen supersaturation is pretty rare and is associated with malfunctioning equipment. It is possible, however, to over aerate your pond, which can lead to lethal levels of turbidity if not promptly remedied. Turbidity is the level of cloudiness or haziness of a fluid, caused by suspended particles invisible to the naked eye. In ponds, it is raised by stirring up sediments and detritus that collects in the bottom or along the edges of the pond. This concentration of suspended particles is similar to smoke, in that it can damage gills, stunt growth, lower disease resistance and cause reproductive harm. It can also make it difficult for fish to find food as well as render the pond wholly unattractive.
It’s not very difficult to set up your pond’s aeration system so that it provides adequate (but not too much) oxygenation, effectively distributes it throughout the pond, and does not induce turbidity. Your primary objective is to circulate the entire volume of water in your pond at least once every 24 hours, though twice is even better. A well placed pump rated at 1/12th the total volume of your pond will accomplish exactly that. For large ponds, you can distribute smaller pumps that add up accordingly. In addition, if your pond is more than 6 feet deep, it’s a good idea to add some bottom aeration. This action circulates water from the bottom to the surface, where it mixes with surface water and disrupts any thermocline, preventing dangerous dead zones. Of course, it’s always a good idea to discuss your pond’s layout and any concerns you have with a qualified pond professional who can help you accurately identify and correct the source of the trouble.