Pond Boss Forums AERATION Systems questions Which way is best

I am trying to decide which way I want to go...using a 1 HP pump I took off a Jacuzzi, draw water into a filter from the deeper parts of the lake with 1 1/2" pvc and then back out into a fountain....or should I go with getting a pump that will pump air into the deeper parts of the lake. I built this 5 acre lake behind my house (about 30 feet)so power is no problem

Hi Don, I also have a small 1000 gallon Koi pond in my greenhouse and you really need to look at the electricity required for your pump. You might find that it would be alot cheaper to get a true pond pump. I am using a 1900 gallon per hour pump that requires 200 watts. My pool pump for an above ground pool requires 750 watts! Am planning on changing over to a pond pump for my pool to save money once I design a filter system. I also am planning on using one in the large pond, 1/3 acre, to run a water wheel and then run back into the pond will help areate the water also. Bob

Hi Don, I also have a small 1000 gallon Koi pond in my greenhouse and you really need to look at the electricity required for your pump. You might find that it would be alot cheaper to get a true pond pump. I am using a 1900 gallon per hour pump that requires 200 watts. My pool pump for an above ground pool requires 750 watts! Am planning on changing over to a pond pump for my pool to save money once I design a filter system. I also am planning on using one in the large pond, 1/3 acre, to run a water wheel and then run back into the pond will help areate the water also. Bob

Don - You can move much more water per hour using injected air on the pond bottom than pumping water with an electrical pump. Example: with a 1/4hp rotary vane air compressor & the PROPER AIR DIFFUSER I can move abt. 240,000 gal/hr. Try moving that much water w/ a water pump. Water is heavy and it takes a lot of energy to move it. It's just not efficient to use a water pump to mix your pond water esp. when you try and throw it into the air "fountain style". However a lot of people do it. Fountains do have benefits but they are not good for mixing the deep, bottom, pond water. Water weight is 8 lbs/gal. Takes a lot of electricity to throw lots of water into the air and the higher you throw it the more "juice" it takes. Electric company will love you.
KEY is the more bubbles you make & the smaller you make them the more water you move. Problem; smaller holes plug up faster. Make as may bubbles as feasable with the amount of air produced. The more cfm the better. Low cfm's produce fewer bubbles and less water is moved. Diffusers are usu. sized for an optimum cfm of air. Look into an air compressor system; electricity savings will pay for itself plus it will do a much better job of circulating more water.

Thanks Bill....I will do it that way for the fish...I'll be able to put HER fountain in and just run it on occasion. BTW, on your profile, you had AIM ????, that's AOL instant messager number. Again, thanks much and you also Bob

Bill,

Could you explain the main purpose of an air compressor and diffuser? I was under the impression that this device was used to increase the DO in a pond but your previous post talks about moving water. Thanks.

Russ

Air compressor and diffusers allow big volumes of low pressure air to be moved to the lake bottom, converted to tiny bubbles which race to the top. Not only does this add air to deep water, it creates a current. Moving air rapidly through water creates an upward movement of water, mixing deep water throughout the water column where the aeration system is placed. Aeration and moving water are good.

Russ - Sorry for the delay; I'm currently very busy with other things. Bob has correctly summarized the basic concept of the air compressor & diffuser. I'll add a few more details. Bottom water in the pond is the first to lose its oxygen due to the high consumption of oxygen from decaying materials lying on the bottom. To a slower and lesser extent (not always), the deep water also loses oxygen from decaying matter falling through it as dead/dying stuff sinks, esp. important when a plankton bloom is decomposing or breaking down and sinking. An air diffuser producing small bubbles that are rising to the surface pulls water to the surface. The amount of air, size of the bubbles and size of the diffuser determines how much water is pulled to the surface.
At the surface where light penetrates, trillions of microalgae (phytoplankton) add oxygen to the water. In an algae/plankton bloom microalgae densities are often 3-12 million cells per ounce of water at least in the light penetration zone. This is why the water has a greenish tint. These cells range from 3um(0.003mm)to 1 millimeter long.
Some oxygen, but not much oxygen (compared to the total oxygen budget of the entire pond)is added to the water from the bubbling action. Mainly because, 1. oxygen is very insoluable in water (low solubility), 2. bubbles have a short contact time with the water and 3. air has only about 20% oxygen in it, not much available to dissolve into water. NOTE: Air diffusers are POOR emergency aerators; but good for keeping the pond water in overall good condition so you don't need emergency aeration.
Your main goal is to get large volumes of "bad" water out of the bottom to the surface where it is "cleaned up" & reoxygenated. Some decompositional gasses also diffuse out of the water at the surface.
Large volumes of water have to replace all the water that is moved out of the bottom to the surface and this water comes from surface to bottom currents that become established from the moving water spreading out away from the "surface boil". This is why it is better to have a stronger surface boil compared to a weaker boil from a small amount or volume of air from a smaller diffuser.
With the pond BOTTOM SEDIMENTS receiving oxygenated water millions of bottom animals can now live in and on the bottom sediments to quickly & and cleanly decompose/eat the organics and recycle them back into the basic chemical nutrients.
In "healthy" oxygenated pond/lake bottom sediments, there can be up to 80,000-180,000 aquatic worms (oligochaetes)per square yard plus thousands of individuals of several different types of insect larvae. This does not include all the protozoans, rotifers, snails, fingernail clams and bottom zooplankton that can also inhabit the oxygenated sediments. They all are responsible for processing the dead organic materials that have settled to the bottom. NO, catfish do not eat this stuff; small critters & bacteria do. Without oxygenated water on top of the deep water sediments none of these tiny animals can live on the pond bottom. I hope this helps you and others understand the benefits of moving your pond bottom water to the surface with an air compressor and diffuser. B.Cody-Pond Doctor

Bob and Bill,
Thank you for the explanation on the function of compressors and diffusers. With the understanding that its beneficial to circulate the bottom water in a pond, would the rate at which water in a small pond (<1 acre) is circulated be any different than the rate required for a larger body of water. Just curious.

Russ

Russ - I'm not sure what kind of information you want from your "rate of circulation" question. The amount of circulation a body of water needs is based on how fast the oxygen is being consumed in the water overlying the sediment. This mud water interface is where the oxygen is lost the quickest. Oxygen loss is due to the biological oxygen demand of the decay/decomposition of the organic material as "bugs" consume the dead organic materials. Organics in ponds are almost always thickest on the bottom.
Ideally. The pond's need for oxygen renewal in the bottom actually determines how often you should circulate or the rate of circulation.
In general, your rate of circulation or how fast you can mix the pond is dependant on strength (volume/flow)of the water moving up boil. With the exact same aeration unit, one can get a higher (faster) rate of circulation (mix the pond volume faster) in a smaller pond abt 1 acre vs a larger pond.

Your diffuser moves X number of gallons per hour. Your pond has X number of gallons. Pond gallons/diffuser flow volume per hr = time required to mix the pond.
Your rate will be greater when you introduce more CFM to the diffuser or add additional diffusers. Providing your pump has some air to spare. If we add too much CFM to a diffuser (more than it is designed to handle) we force the bubbles to be larger and reduce our circulation efficiency causing less volume or flow). Based on how many gallons your diffuser moves will depend on how long you need to run it to circulate the pond at last one circulation.
At the surface the boil from the diffuser only spreads the water just so far based on volume of the upwelling water and somewhat on wind speed/direction. A "wimpy" boil from low CFM does not spread the water very far and doesn't have much force which produces less circulation or more time require to circulate the water. Thus circulation is not as good as with a stronger boil from putting more CFM to the diffuser.
DID THIS ANSWER YOUR QUESTION?

Bill,
Sorry for the vagueness of my previous post. I read your response and yes, you did answer my question. Every pond will have characteristics unique to itself and the rate of oxygen consumption is only one. I certainly appreciate you taking the time and patience to answer my questions. Now rest up a bit because if my previous post had you grabbing for oxygen, the next one I'm working on is certainly going to lead you to the deep water........

Russ