Pond Boss Forums AERATION Should I aerate? When To Quit?

I am located in Central Indiana and I have been aerating my pond using a rotary vane pump and airstones. One of the airstone units is in about 25' of water and the other two units are in water that is between 5' to 7' of water. My question is when should I turn off my aeration? This question has probably been answered a thousand times so if someone could tell me a good keyword to use in the search I will look up the info. Thanks in advance for any help, J. Street.

Joe,

Scroll down two posts for answers to your question.

Thank you Cecile, I feel like a knucklehead. I did a search for winter aeration and found the same post

Hi Joe, you have me curious on your post, What is your pressure reading and is your rotary vane a high pressure model as 25 ft can be of concern for a lot of vane type pumps. If it states .69 bar or 10 psi on the pump decal and your guage is at or over 10 psi consider moving the 25 ft stone to 18 ft or so to prolong pump life, Good Luck Ted

Ted, sorry I didn't respond to your post back when you posted it. I must have missed it when you posted it. I was reading old posts trying to figure out when I should turn my aeration back on when I came across it. To answer your question my compressor is a Sweetwater AQ7, it is rated at 10 psi, I checked the pressure gauge on my pump and it is reading about 5 psi. The thing is I have two of the air diffusers shut off for the winter and I have one running in about five foot of water that is close to the end of my pond just to keep the ice off of it. I was looking at the AES web site and it looks like the compressor I have is only rated for 18' like you recommended. Since I have the two diffusers shut off I assume when I turn them back on and pump the air to 25' it will exceed the 10 psi recommendation. I have a buoy tied to the air diffuser so it shouldn't be too big of job to pull it up and relocate it. I have a pretty heavily stocked pond, will I lose any benefits of aerating by putting the diffuser in shallower water? I would hate to purchase another pump but if I did I suppose I could use the 10 psi pump for shallower water and the new one for the deeper parts of the pond. The 25’ depth only covers about ¼ acre of the pond. Also any recommendations on turning the air on to the other two diffusers? Any help, suggestions, comments will be appreciated. Thank you, Joe Street.

Hey, Joe - Did you find out when to turn the aeration back on in the Spring? I'm starting to wonder about that myself. Gotta start taking water temps regularly again.

Theo, haven't figured it out yet. I'v got to pick up a thermometer. Had one for the Koi Pond but it has dispeared. If you come across any good posts on the subject please let me know. I threw a handful of food into the pond the other day not really expecting anything but the BG came up and ate it although it wasn't with their typical feeding frenzy. Still too cold I suppose.

Joe and Theo, Still plenty of DO in midwest ponds with the weather we have been having. Mother nature is mixing more than most aeration systems are designed to do so I wouldnt be in any hurry, Perhaps a month out yet unless it turns to summer next week (and it could)I have not done any DO or bottom temp checks for several weeks as I know most ponds in Ohio and Indiana are at least 80-100% saturated and probably have at least 9 ppm DO.Perhaps Cecil is more current on the readings. Joe as far as your aeration system running at 5 lbs the AQ7 (3/4hp Gast) creates 9.5 cfm at that pressure,(8.8 @ 10 psi) If you have that much cfm going to one diffuser it should be boiling "big time" If you have the 4 stone setup per diffuser (ALA4GL the cfm range is 1.5 to 2.4 each and the ALA6GL is 3-7 cfm with 6 stones per diffuser)In order to keep your pressure as low as possible (which you want to do) be sure those stones are removed yearly for cleaning per the AES Sweetwater instructions. If you dont have the instructions I have them posted under "A word about diffusers" on my home page, also when you have them out if there is a 3/4 inch blue "Brady" checkvalve where the tubing connects unscrew it apart and remove the spring and the pump will have to work a little less. AES started removing those springs a few years ago but I still find many systems and diffusers with them in.As far as replacing your pump it is not needed as just making some minor changes may be the only thing needed, you have plenty of pump for a 2.5 acre pond.Let me know if you have the ALA 4 or 6 and check into the check valve issue. While your at it and have the checkvalves apart see if the o rings are cracked as they usually are after a year or two.If your Sweetwater does not have the two end caps filters and most Sweetwater units do not, consider the dust from the sacrificial rotary vanes are probably collecting on the inside of the stones thus one of the reasons to clean them yearly.Lastly I would put the one diffuser in 20 ft of water and watch the pressure guage and slide it deeper until the guage is just under 10psi, putting it just under 10 psi will give you room for 10% additional backpressure as the stones slowly get material either in them or on them prior to the next cleaning.Also if you have a liquid filled pressure guage be sure it is "vented" at the rubber fill plug on the top as these guages are normally shipped unvented and will read pressure without venting but not accurate.Good Luck Ted

Thanks, Ted. I guess good heads-up pondmeistering would be to keep track of weather (wind and rain contributing to oxygenating and mixing) as well as air & water temps. If we assume bottom temps coming out of Winter are a little above 39 degrees F, we can track how well the whole pond is staying mixed by watching the surface temp. I'm not in a big hurry to haul the canoe down to the pond and check bottom water temps yet.

Joe - The longer you wait to begain aeration in spring the warmer the surface water will become and the stronger the stratification layer will become. We have found that when you start up aeration with a diffuser at shallower depth than the deepest point then it is harder for the aerator to pull the water out of the deepest part/basin. In some instances (esp mid-summer start up) the deepest water will stagnate in the deepest section and the pond only circulates down only to the depth of the deepest diffuser. To prevent this we found that if you begin aeration when surface temps are less than 50F this problem does not usually occur. Thus I tell people to begin mixing at or before 50F average surface temps. If your diffuser is in the deepest part of the pond then this is not usually a problem and aeration can begin when surface temps are around 55-60F.

As Ted mentions, keep your air stones and check valves clean to mimimize air flow pressure for the pump. Mineral deposits from water are the main reason the stones clog. The nose cone will unscrew from inside the blue check valve to allow for better and more complete cleaning. The beveled rubber washer in the checking mechanism will crack then leak as it gets old. At that point you might want to replace your diffusers with the membrane type. Ted has high quality self checking diffusers when ever needed.

Theo you got me curious on the temp and DO and as I did not want to drag the boat out either here is what I came up with off of the pier. Temp at 2 ft 7.1 C (44.78F)DO 11.3 ppm 94% Dropped to 12 ft water and 6.8C and 10.8 ppm DO,This bottom temp surprised me somewhat. High on Sunday 65F with the next 4 nights all lows in the middles 20's and lots of wind.Mother nature aerating at her best

I got 46.1 deg F surface temp and 45.4 deg F at 3 feet today.

Ted, I have the ALA6GL diffusers on my system. There isn’t a check valve on the airstones. On my blower there is an air filter on the intake side but not on the output. So I probably am getting dust from the vanes in my airstones. I just replaced the graphite vanes last month although the old ones were only wore down about a third after a year of operation. I have a bypass valve on my compressor that allows me to blow off excess air, my one diffuser is bubbling to beat the band but I’m not putting all of the air to it. I had planned to clean/replace the airstones when the water warmed up a little bit. Bill Cody mentioned the membrane type air diffusers, I have a Koi pond that is slightly over 60,000 gallons and I use these. They are built into the domes that cover the four bottom drains. They seem to work very well, do you have a preference? They do seem to be less maintenance, from what I understand if they start to get clogged all I have to do to clean them is to crank up the air and that will expand them enough to unclog them. Thanks for your help, Joe.

Bill, in your comment you noted that you recommend to people to start mixing at or before 50F average temps. What would be the coolest temp. that it would be safe to start mixing? Thank you for helping with my questions, Joe.

Joe, Im surprised you do not have the inwater check valves as I have not seen these stones without them even when a check valve is on the intake airfilter.They may no longer be blue in color and appear to be a 3/4 inch coupler sometimes instead of a check valve. Rotary vanes build extreme pressure (30-40psi) when they have to clear the airline of water on startup with out these check valves, This is a heavy load for bearings and starter switches until the pressure is back down to normal operating pressure (5-10 psi) Perhaps you are bleeding off on startup and slowly putting the air to the diffusers which will work also.As far as the smaller pond if you have 4 of any type of diffuser in that small of body it is probably well aerated.You are right about the self cleaning aspect of rubber membrane diffusers and their ability to self clean by "flexing" and then returning or rebounding to normal operating pressure. Mineral deposits are no longer a concern. There are a few different types of rubber membranes on the market. Some have limitations on the amount of cfm you can apply to them so they do not stretch and lose the builtin check valve function.When looking at diffusers of any type the total length of run of tubing (friction loss) should be considered also.Some membrane diffusers cause more backpressure than others.Even though they will have the same water pressure on them at the same comparative depth (approx 1 lb per 2 ft of depth)If concerned about spring startup try running 1-2 hours the first day and doubling your run time each day until you are at 24/7 (4-5 days) when the air temps( and top water ) averages 45-50 F minimum,This is a conservative startup procedure but one that works well vs going straight to 24/7. Ted

Ted, I’m pretty sure that there is no type of check valve at the diffusers. There is a blue “Brady” check valve on the compressor that is approximately 3” long. I checked my water temp. today. At the surface it was 51F and at 3’ it was 50F. I used a digital meat thermometer because it was the only thing handy so accuracy may be off a little bit. I decided to turn on all of the diffusers; first I opened the valve to the deepest (25’) diffuser and cut off the valve to the shallowest water diffuser, when I did more air escaped from the bypass valve on the compressor and the gauge never showed pressure above 8 psi. I then opened the valve to the diffuser that is in about 7’-8’ of water and then I opened the valve on the diffuser that is in 5’ of water. I have to throttle back the two valves that are connected to the diffusers that are in the shallower water to keep air going to the deepest water diffuser but at no point has my pressure gauge went above 8 psi. All of the diffusers are blowing a fair amount of air. Should my pressure gauge be reading a higher pressure? I’m pretty sure on the depth of the deep water diffuser because I tied the end of a 25’nylon rope to the diffuser and the other end to a buoy and the buoy stands up like a fishing bobber when the pond is completely full as it is now. I suppose that my pressure gauge cold be bad, it is a liquid filled gauge and it does have some air in it, I just have to figure out how to burp it, due to the angle that it sits in the housing I’m going to have to pull it off to get the air out of it. Thanks again for your help, Joe.

Joe - Some in my area start aeration as soon as ice is off and water is 39F. This early aeration does not appear to cause problems in their ponds. Although Mother Nature will relatively well-mix most ponds until the surface temps get into the 50F+ range. The warmer the water gets above 40F the more wind action it takes to mix surface water to the bottom.

Your byPass valve (pressure relief valve) seems to be set to blow off (release) at 8psi. This assumes your air guage is accurate. If you are able to push air at a true 25 ft deep then the psi at the pump is 12psi. Air pressure at pump will reflet the head pressure of your deepest diffuser. If your pressure guage is liquid filled (glycerin) then there is supposed to be a small air space at the top of the guage. There often is a small rubber plug at the top of liquid guages to allow one to equalize the air pressure between the internal guage air space and the atmospheric air pressure. Some guages have a rubber plug at the top that you can stick needle into to allow the pressure equalization.

NOTE - In my earlier post I mentioned that ponds may not mix completly with diffusers not placed in the deepest part of the pond. This often occurs when aerator start up occurs after the pond reaches temps higher than 50F. A qualifier needs to be mentioned. These ponds can USUALLY be completely mixed with extended operation of the aerator. As the aerator warms the bottom water, this unmixed bottom water will gradually become warmer and gradually the stagnant layer becomes incorporated into the whole circulation pattern. There are variations and exceptions to this phenomenon based on several variables specific to each situation.

Joe try this> with the pump running, slowly close down the 2 shallow diffusers and see if the guage will read 10 or 12, you may have have to partially close the 3rd valve also and readjust the relief valve. If you cant get a reading of at least 10 psi either the guage is not correct or the end plate ( not the contact surface for the vanes)in impeller box is scoured ((motor bearings starting to go bad)due to wobble in the shaft. This causes pressue loss within the air box.Think of it like bad compression in an engine that has good rings but a bad cylinder wall.If you cant build pressure let me know and Ill send you some pics of the situation and the fix. You should be able to build 20 psi easily with that pump (but dont)Regardless you are still pumping air you would just not know how much,Hopefully its a guage issue. Ted

Ted & Joe,

There are two more areas to check. Joe, you said you just changed the vanes on the compressor. Did you scrape the old gasket off the muffler box? The gasket looks like an apple cut in half. If so, make sure it is not pinched or pushed or buldging out.

Second area to check would be the lines that connect from the compressor to your weighted tubing. Those fittings are known for either melting under higher temps or at least becoming loose and alowing some air to escape.

Otherwise, I agree with Bill about when to start your system, just after ice-off.

Cary, I checked the lines and they are o.k. I did replace the gasket when I changed the vanes on the compressor, It doesn’t appear to be leaking around the seam on the muffler box. I appreciate you responding to my question. Thank you, Joe.