Pond aeration is the amount of oxygenated water in a pond. Oxygenated water reduces algae growth and enhances the growth of beneficial bacteria in the water. The water becomes clearer and less muck accumulates at the bottom of the pond. (Muck produces noxious air bubbles which further deteriorate the pond’s overall health.) Fish need oxygen to survive, and aeration provides their needed oxygen. On top of that, by aerating the pond, de-stratification occurs. Stratification is the dividing up the pond into different layers, usually with colder layers at the bottom. Aeration provides oxygen to all the layers and mixes them up so the divisions in layers disappear.
Now a certain amount of aeration occurs naturally, for example, as a result of wind. But often pond owners need to add oxygen to the pond by installing a floating fountain, either a decorative fountain or an aerating fountain.
Many, or perhaps most, pond owners believe they can determine aeration of a pond by horsepower of the motor. This is often an inaccurate way to determine how much aeration will occur. What matters is the flow rate. You see, pond fountains aerate by pushing up water outside of the pond, where the water bubbles mix with oxygen and then fall back into the pond. So what matters is how much water flow is pushed outside of the pond into the atmosphere and then returns to the pond.
Some 1 HP pumps only have a flow rate of 7,000 gallons per hour, whereas some 1/2HP pumps have a flow rate of over 10,000 gallons per hour. In addition the pump’s flow rate is not the same as the net flow rate. With decorative fountains, for instance, which use impellers and nozzles, the nozzles by design restrict flow rate, as the water released must flow through the nozzle’s holes. Nozzles decrease overall flow rate by design. Aerating fountains, by contrast, do not have nozzles but use a propeller, so their flow rates are different. The featured image of this post is a closeup of a Kasco aerating fountain. You can see by the image that flow rate will be high.
Let’s say you have a 1/2 HP pump with a pump flow rate of 10,000 gallons per hour. If a nozzle is used, the flow rate will be restricted by it. The pump flow rate of 10,000 gallons per hour might be reduced by the nozzle to 4,000 or 5,000 gallons per hour. An aerating fountain will not have as much restriction; still, if the pump flows are 10,000 gallons per hour even an aerating fountain will reduce flow rate by a certain degree.
Likewise, claims about horsepower are also quite suspicious. Very high horsepower ratings claims are often made about very small pumps that use very low wattage. That’s not possible since the pump’s horsepower and wattage are related. We suspect some companies are citing input horsepower but really what’s more accurate of what a pump is accomplishing is output horsepower.
We are not trying to over-complicate things for the customer, but we would like to remind that aeration depends on net flow rate, not horsepower.
