Dissolved oxygen is a critical part of the ecology of a pond. It is what makes the pond circulate, what allows the koi to be healthy, and keeps the water clean. Dissolved oxygen is actually gaseous oxygen, which is dissolved, in an aqueous solution. In most ponds, the average is 5 ppm. Anything below that can lead to problems. There are unfortunately many critical problems that may result from this.
FISH KILL: Fish require a certain amount of dissolved oxygen to live, and if they do not have it they will
POOR OXYGEN LEVELS: They lead to noxious odors coming from the as the break down of organic
waste shifts from an anaerobic process to a slower process, resulting in hydrogen sulfide
production. In deep ponds, lack of oxygen will result stratification, the resulting layer at
the bottom of a pond that becomes useless because it is oxygen deficient. This results in a
reduction of the available living space of koi, putting more stress on the still oxygenated
water. There are many issues that cause oxygen levels to lower.
ABUNDANCE OF AQUATIC PLANTS: They are good in moderation, being
that they release oxygen into the water. In the case of algae, planktonic algae
sum up the base of the food chain in a pond. Many of these plants that release
oxygen during the day also consume it at night. When you have a pond with a
heavy algal bloom or thick vegetation, oxygen may be quickly consumed
overnight and even on cloudy days, leading to a FISH KILL.
HIGH ORGANIC WASTE LOAD: Organic waste in a pond may come from a
range of sources such as dead vegetation, fertilizer run-off, fish food, and fish
waste. All of these are broken down in a pond naturally, but in order to do so
efficiently and without further damaging the water quality, oxygen is needed.
There are two types of aeration systems to choose from: SURFACE AERATION and BOTTOM BASED AERATION. You can figure out which works best for you by using the average depth of your bond as a barometer. If your pond is less than six feet deep, the surface aeration will work, while deeper bonds will benefit from a bottom based aeration system.
Surface aerators are floating aeration units that pull in water from the top foot of the pond and splash it into the air. When the water crashes back down onto the pond, the oxygen transfer takes places. Since the oxygen transfer takes places at the surface, these aeration systems are best for SHALLOWER ponds. These units can be equipped with different spray patterns for better appeal, but the more extravagant the spray, the more usually less efficient the aeration is.
Bottom based aeration system, or diffused aeration involves the act of pushing air down to the bottom of a pond to allow bubbles to rise to the surface. These units are most efficient for aerating deeper pond and lakes since the bubbles provide most of the work. However, these system can be used in shallower ponds, but they would need to installed evenly throughout the pond, which would in turn cost more. When the bubbles rise, they de-stratify the water eliminating the oxygen poor zone at the bottom and mixing it with the oxygen rich water above. This then creates a healthier water column. These systems also create very little surface agitation.
Make sure you receive assistance in sizing a proper aeration until for your pond unless you have a very round, even depth pond.
Once you have a properly sized aeration system, your bond will benefit in many ways including:
FISH KILLS: will be prevented due to low oxygen
MAINTENANCE PRODUCTS: reduced to the ponds natural ability to sustain itself
BENEFICIAL POND BACTERIA: stimulated to break down waste and reduce bottom much layer.
Aerobic bacteria will overcome anaerobic bacteria to control odors.
KEY NUTRIENTS: phosphates are unavailable and metals such as iron are precipitated out
POND WATER: de-stratified leading to the prevention of turnover and improved water quality
ALGAE BLOOMS: less severe and less problematic because of the lack of available nutrients
GASES: carbon dioxide and hydrogen sulfide may be vented
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