Fountain or Aerator or Both?
Fountains do certainly aerate, but they aerate less than a plain old simple aerator. So what is best for you is always a judgment call.
You see, fountains use impellers and a nozzle to produce their beautiful displays. The nozzle has to restrict flow in order to create the display. Holes are punched or drilled or molded into the nozzle, and where there is no hole, no water exits. So flow is reduced. This reduction in flow is typically greatest when displays are tall and wide. To get the water to “squirt” higher and wider, hole size is reduced to create pressure.
(above nozzle with many holes creates display on right)
Kasco recommends a two-horsepower decorative fountain for every one-surface-acre of pond. For a surface aerator, Kasco recommends a one-horsepower unit, and flow is not restricted and a propeller instead of an impeller is used. (It should be noted that these recommendations are for Kasco units, and Kasco has their units independently tested for honest assessment. We have tested other pumps that advertise at 1/2HP or 1HP but could not replicate those measurements.)
Surface Aeration versus Bottom Aeration
Most people are familiar with surface aeration. You’ve seen pictures, no doubt, of the enormous fountain at the White House. The action is occurring at the surface of a small pond. Though that fountain might be stationary, most surface aeration for ponds consists of a floating fountain design.
In this design, a pump is suspended by a float, typically black to blend into the water. When the water level lowers, the float falls with the water level. When the water level rises, the float rises with it. To keep it in place ropes are attached to the float and are either attached to cinder blocks or other weights at the bottom of the pond or tied to the shoreline.
The Different Kinds of Surface Aeration
Display (Decorative) Fountains
Display fountains create the most intricate displays. As noted above, the pump uses an impeller instead of a propeller. Typically several different nozzles are either are available or come with the kits. Kasco recommends 2HP pumps for every acre of pond, but that is only because Kasco units provide lots of aeration no matter what. If you are using a non-Kasco fountain, you can typically expect needing lots more HP per acre, depending on the impeller and the shape of the nozzle. But if you are mostly worried about decoration and not aeration, you can buy big displays from all kinds of manufacturers of decorative fountains. Scott Aerator offers very large fountain displays, for instance.
Pump with impeller
Aerating fountains use a propeller instead of a pump impeller, and are more efficient than display fountains. A tradeoff is that they only have one pattern, the V-pattern, and heights of displays are lower than with decorative fountains. Kasco recommends a 1.5 to 1HP ratio. For every half acre of pond surface, a .75 HP unit should be used. Again, these are Kasco specifications, and level of aeration varies from manufacturer to manufacturer.
A pump with propeller
Surface Aerators use a propeller, too, but concentrate solely on aeration. They provide double the aeration of a decorative fountain (at least with regard to Kasco units). There is no nozzle and little display, though they can be radiant at night and are capable of terrific aeration.
Bottom Aeration Using Diffusers
If your pond is deeper, on average, than 7 feet, bottom (diffuser) aeration works best. An air compressor is located at the shore and a hose carries the air to a diffuser unit at the bottom of the pond. Compressors vary in noise, though the Kasco units are relatively quiet if properly housed. They are also very energy-efficient, and a great deal of aeration can be done with a quarter horsepower compressor. They need to be housed to protect from the elements, thus quieting them more. If your pond is shaped conventionally, as a rectangle or oval, then it’s often the case you will only need a single diffuser at the bottom of the pond. If it has islands or unusual shapes, there’s a good chance you will need to place more than one diffuser at the bottom.
Multiple Kasco diffusers for extremely large ponds
Combining the Two Kinds of Aeration
If you have a deep pond but still want to see a fountain, you can combine the two types of aerators. A pond aerator system could use a surface fountain for display and agitation of water. You might even use tall and wide displays in relatively low amperage pumps, if you are only worrying about display. The bottom diffuser system would properly increase dissolved oxygen levels.
Why Ponds Need Aeration
Aeration is needed for fish health. One of the worst things that can happen to a pond is fish kill, which occurs when there is too little dissolved oxygen in the pond. But even if you don’t have fish, without aeration, the pond ecosystem is disrupted without proper aeration. The surface becomes stagnant and the bottom of the pond accumulates muck. Beneficial bacteria are reduced. Plants, including algae, in the pond need oxygen in order to decompose, and if they don’t get enough of it from proper aeration, old plants will decompose faster than new ones, and the muck sends up gas bubbles which can create a terrible smell.
Sizing your Pond
We have calculators to size your pond’s total acre feet and gallons of water, and also calculators for estimating electrical cost. You can see the calculators here.