First of all, though aeration occurs naturally in ponds, additional pond aeration is often necessary. A proper pond aerator is necessary to insure the health of your fish and the entire pond ecosystem. But what kind of system is right for your pond depends a lot on the pond’s average depth.
Lack of aeration causes your pond to stratify, form layers in the water; typically these layers are different temperatures with different levels of oxygen. The top of the pond can become stagnant and full of muck. Also, muck will accumulate at the bottom of the pond, and it will become shallower over time. Plants in your pond, including algae, need oxygen to decompose. And if they don’t get enough oxygen, the old plants will decompose faster than the new ones, sending up noxious gas bubbles from the bottom. A pond aerator system will de-stratify your pond and result in less chance of a fish kill and bad forms of algae and other noxious weeds.
Aeration Reduces Stratification (Layering) of Ponds
Pond 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, ponds create stratified layers in the water, and the bottom layer is depleted of oxygen. Also, the pond surface can become quite stagnant and full of muck. The accumulation of muck will cause your pond to become shallower over time, perhaps necessitating dredging. 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 an awful odor. You don't want your pond looking like this photo.
Common Ways to Aerate
Basically, there are two different ways to aerate, from the top of the water and from the bottom. Whether to get a surface aerator or a bottom aerator or both depends on your pond depth and the overall goals for your pond.
Aerating from the surface is the most common. A float sits on your pond, usually black to blend in the water, and a pump is attached to the underside of the float. The float allows the whole unit to rise and fall with the water levels. But what kind of water flow and thus aeration you get depends on which kind of surface aeration you choose.
Decorative Surface Aeration
The most common type of surface aeration is the use of a decorative fountain. A nozzle sits on the float attached to the pump. The display can be quite dramatic and complex with several angled holes--or be simple. A decorative fountain pump will use an impeller
Aerating Fountain Aeration
An aerating fountain will provide more aeration than a decorative pond fountain. Instead of an impeller the pump will use a propeller. Also, the “nozzle” is basically a large hole, which provides only the V-shaped pattern.
Plain Surface Aerators
There is one other kind of surface aerator, and this one provides the most aeration of all, probably double of what a decorative fountain will do. A propeller is used for surface aerators, too, but there is no nozzle at all, and thus no restriction to water output. There is also little display, just large splashing bubbles.
Bottom Aeration Using Diffusers
The thing is, if your pond is deep, with an average of over 8 feet, bottom 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. Though compressors used to be rather loud, nowadays they are much quieter. 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.
We really think the Kasco pond aerator system is the best bottom aeration on the market.
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 below, and the diffuser system would properly increase dissolved oxygen levels. The fountain would not need to aerate as much and could focus on beauty. This focus allows for a greater range of price as well as dramatic viewpoint.
You can add lights to any of the surface aerators, even pure aerators.