Pond Boss Forums AERATION Should I aerate? Aeration simplified

RC51 -Very good questions. In my experience the shallower and smaller a pond is the better a windmill tends to aerate primarily because small shallow ponds require less circulation compared to larger deeper ponds. It is all about average depth and water volume. A single windmill does not provide adequate circulation in the 'average' pond larger than 0.25 to 0.7 ac, especially during adverse conditions. During warm temperatures, clam winds, and algae blooms, expect dissolved oxygen sags and fish kills when a windmill is the only source of aeration mixing. If high quality fish are important for the pond, I would not depend on windmill aeration.

This thread is very interesting to me. Being a farmer, doing something like putting in aeration in a "farm" pond seems a little sacrilegious. There was no intention of doing it during construction and I kind of sloughed the idea off when the guy who sold and delivered my stocking fish mentioned "it is never too early to think about aeration".

Well when the filamentous algae started showing up, since we look at this pond out our kitchen and bedroom window, it was not a satisfactory "look" to wife (or I have to admit, myself also). So I have been studying aeration and will be following this thread through the winter.

What I have observed and think I know so far which is very little:

I ordered a relatively inexpensive linear pump and dual 9" membrane round diffuser, put it in a few weeks ago at about 8'-9' depth and took it out yesterday for the winter. It was temporary, never meant to be permanent (will do that next spring) and was mostly an experiment so I could learn something this fall while the water temperature at least had not went completely cold (although the pond I think had already "turned" and lost its heavy summer thermocline).

Some observations from someone who up until now only knows what I have read in the last couple months and have had about three weeks observation of the diffuser in operation:

The dual diffuser moves a significant amount of water. On a clam day I was surprised when I paddled my small boat up to it how well it pushed the boat away with the current. According to a 15 psi gage it was running at 3.75 psi. The gage was not an expensive one so I would not put great faith in the accuracy of that measurement, but it should be ballpark based on about a 9' depth with the diffuser base raising it up to 8 or 8.5. Again not a real accurate measurement on the depth but should be close. On a perfectly calm day you could see the ripples go all the way from the diffuser in the southern third of my pond all the way to the north shore. I'm certain I do not have enough diffusers or pump capacity for the whole pond (I am leaning towards 3 on a 3.5 acre kidney shaped pond) but as I said this was just a learning experiment till I decide what the permanent installation will be.

I was impressed with the amount of water being moved. I think it was starting to improve clarity but hard to tell in such short period and maybe it was just wishful thinking.

The small fish loved it. Adult FHM and small BG of about the same length when the water was still warm would ride the current to near the surface and jump off. Since I did not have them individually identified, could not tell if the same individuals were riding the "roller coaster" from the bottom to the top only to do the ride again, but it sure looked that way as it would be a continual stream of fish bubbling out of the stream of bubbles and current. I was observing from a small paddle boat. On approaching, the fish would temporarily disappear from being spooked by the boat, then quickly reappear and start the ride over. They seemed to love it. This pretty much stopped once the water got below about 60 degrees though. Was quite entertaining and something I did not expect to see.

I put in "lots" of structure in the pond. My small paddle boat (Paddle King) is equipped with a Garman 200 fish finder and we have fish all over the pond. But near the aeration and the structure nearest it, there appeared to be an even higher concentration of fish. Could be coincidence, could be they liked the diffused air and the current it created. Got the fish finder right after the air diffuser so have no previous reference.

My observations to date and until spring comes.

snrub

One other question about aeration vs moving the water via mechanical means.

If a person put in a windmill before the pond filled, in the pond, would the energy from the windmill be more effectively used by turning a mechanical agitation device directly? Or is its best use pumping air and using bubbles to move the water?

Somehow I think the better use of the windmill power would be to mechanically move the water from lower to the upper part of the pond, but I could be wrong.

It seems the deal with pumping air is it is more efficient to move the water by an air pump when buying electricity. But with a windmill we are not buying electricity. Instead we are making an investment in hardware and we really do not care about electric costs. So maybe there is a more effective way to move water with a windmill other than an air pump? Seems to me it is going a long way around to move water with a windmill that was originally designed to pump water.

Ideas?

snrub

The fish LOVE the bubbles - little fish hide in them and the preditors hang out around the perimeter.

Think about the logistics of mechanical aeration, when compared against pneumatic aeration. Mechanical means moving parts, and the transmission of force required to do the work from surface down to near the bottom....in an underwater environment. Moving parts require adjustments, maintenance, and eventually repair or replacement. Pneumatic aeration involves a flexible hose, and some plastic and flexible membrane diffusers..no moving parts, and if maintenance or repair is needed you simply pull the diffusers to the surface and get after it.

I do think that surface aeration might hold promise for windmill application.


I'm also still sayin' the stirling cycle powered compressor holds promise for aeration!

If one does the homework for amount or volume of water that can be pumped by the windmill vs amount of water moved from the air produced, I am very confident the air pumping will move more water. I have data for the amount of water volume and cfm of air a windmill can pump and it is significantly less water volume than what 1cfm of air can move water to the surface. Do the home work to verify my comments. Many windmills have pumping capacity. Some diffusers have volume ratings per cfm of air.

Please prove me wrong with references if the following is not correct. Do not expect aeration to significantly reduce FA growth if and importantly if the nutrients feeding the algae are sourced from dissolved nutrients in the inflow water such as from the watershed or manual fertilization. Many new ponds have FA algae problems due to the 'fill' water containing dissolved fertilizers (nutrients) and or from nutrients leaching from newly exposed dirt. Fertilizing the watershed to grow grass can result in heavy FA growths after rain events. Aerators do little to precipitate or bind incoming dissolved nutrients or manually fertilized nutrients (N & P) in the water column. Aerators can help reduce the amount of nutrient recycling and phosphorus accumulation in the anoxic hypolimnetic (deep) water, especially phosphorus, from the sediments due to anaerobic conditions and decay.

Aeration appears to work best when the phosphorus concentration is at or slightly above that level an aerator can diminish or suppress phos primarily in internal nutrient recycling. In these instances, an aerator appears to work 'wonders' at reducing algae growth. Aeration prevents stratification and reduces nutrient build-up due to reducing anaerobic conditions above the sediment water interface. However when phosphorus concentrations are a lot higher than what an aerator can reduce, then high amounts of algae growth occurs due to excess nutrients and the aerator appears to have little affect at reducing algae even though it did reduce some phosphorus but not all required to grow some algae. Very little published data is available on this topic. If one has a alkaline rich pond with low algae growth and then if granular or liquid fertilizer is added, noticeable algae growth will occur despite having lots of aeration and/or if excessive aeration is added.

In regards to fish activity in the bubble plume, the fish are attracted to the bubble plume because it contains high amounts of zooplankton that are carried from the bottom zone to the surface in the upwelling water. Small fish feed on the zooplankton buffet and larger fish feed on the smaller fish. Fish feeding in the bubble plume is most noticeable during daylight when most zooplankton are inhabiting the deep water which is a common occurrence for most 'forms' of zooplankton. The majority of zooplankton are diurnal and migrate up and down in the water column daily. They inhabit the deeper water during daylight and near surface water at night.

If going the windmill rout, I would use it for electrical generation and stored energy rather than something just mechanical. That way, you can select higher efficient methods like Sue's bubbles or Brian's surface rig.

Thanks for all the replies. Very informative.

I was thinking of a windmill driving something like a propeller via a gearbox and shaft rather than a traditional water lift type pump that might be used to pump water.

Mostly just idle thought processes concerning the wind mill. Nothing I am close to seriously considering.