Pond Boss Forums AERATION Should I aerate? Windmill Aeration

RUSS - From Pond Doc: I'll try to cover most of the points regarding your two questions.
1. Pitfalls in pond design that hinder bottom air injection for aeration or mixing. A. Pond Shape & Basin Design. Now keep in mind that I am talking about the best THEORETICAL ideas for aeration/mixing water and not about the best designs for fish production and fishing or scenery/aesthetics.
The aeration surface "boil" or upwelling that occurs from bottom aeration is an outward circular flow pattern. The movement of this boil and how far it reaches outward depends on it's strength which is dependent on how big the diffuser is and how much air is put into the diffuser. More & bigger obviously produces more.
B. A 2 feet dia. diffuser receiving 3-4 cfm will produce surface currents that can travel upto 100 feet away from the center before dissipating. Wind can also extend the "reach" of the boil. Thus, for optimum efficiency from the boil and best circulation from one diffuser the pond should be round with the sides slopping down to a funnel. The more embayments, backwater areas or bends in the shoreline the more diffusers that will be needed to cause circulations or mixing into those "secluded or isolated " areas. Big ponds (>2 acre) usually need more than one diffuser. Larger hp & more air producing compressors are often necessary to get GOOD circulation in the larger elaborately shaped ponds. (I have a 3/4 ac pond that has 3 diffusers run from one 1/4hp compressor.Two of the smaller diffusers are in "finger areas" away from the main basin. I run this aerator 3.5 to 4 hrs/day which produces good mixing in all areas). Running more time would be necessary to circulate more water in a larger pond.)
C. An island deflects the flow & prevents water currents from reaching back side areas. Ponds with islands usu. require four diffusers; one on each side for proper water circulation.

2. Within reason, you cannot over aerate unless you turn your pond into a food processor (too violent of circulation). This is the method used by sewage treatment plants. Too strong of currents will resuspend light fluffy sediments and create cloudy water conditions. But once you have the water mixed or old oxygen poor water replaced with "new" water with oxygen in it, I see no need to continue mixing. Shut the compressor off. Mixing should be resumed or restarted when the water looses enough oxygen that all the bottom oxygen "breathing bugs" begin to get uncomfortable and start needing more oxygen for survival and daily activities. Usually in many ponds this is once a day. To error on the safe side, we often recommend mixing twice a day & splitting the overall time into two run periods; morning and evening. (We have never tested w/ oxygen meter and temperature sensor which way is best. I can make a strong case either way. The tests are future homework).
Ponds with small or under sized circulators may have to run 24hrs to get one complete mixing & water/oxygen renewal across the entire botom.

NOTE: A round pond is not the best shape for growing the most amounts of natural fish food and fish. Lots of shoreline and shallow structure - weed filled littoral areas do this best (production areas), but they hinder circulation currents from aeration. Can't have both very easily.
Bill Cody-Pondoc