I am struggling with the concept of DO levels in my little 1/4 acre pond.

The aeration system currently runs from 3am to 8am and the water temps and DO readings (among all the other test results) are consistent throughout the water column when the system shuts off, so I know the pond is getting successfully turned over at least once and probably twice by my calculations in this time period.

Last weekend's morning tests resulted in water temps at 75 degrees F top to bottom, DO levels at 4ppm from the surface down to about 2-3 feet, and secchi reading at 23". Aeration had just shut off for the day and by the time 6pm, rolled around, I had the following test results...

Water Temps - Bottom 75 F - Top 82.

DO - 6.5 ppm @ surface, 4.9 ppm - 12" down. 4.0 ppm - 24" down.

secchi - 23" (stayed there all day long)

This suggests to me that the current algae bloom is really helping the upper water column with respect to DO (still not all that great really). Whereas the aeration system appears to not do so much for me. Maybe it is keeping the DO from really falling off at night, but it kinda looks like it's ruining the upper levels of water.

I am wondering if mixing in the algae bloom at night is hindering the overall DO levels. My thought is that an algae bloom strengthens during the day, makes decent O2, then at night it gets mixed throughout the water column and has to struggle again the next day to build back up.

I am currently going to gradually increase my air time and check the water next weekend to see what it does.

Somebody straighten me out...surely I'm missing something in my logic. AND, what should I try to do to improve these DO levels?

I don't aerate, I rely exclusively on algae blooms. However, we have completely different bodies of water. Considering you secchi disk readings, I would be inclined to favor more aeration. The clearer your water becomes, the less you will have to rely on aeration. Mud bugs will ensure you always have turbid water to a degree, necessitating aeration.

Also, the bottom of your pond is the key to the water quality. How thick is the muck on the bottom?

To state it simply, I don't have a clue

Nice Joey, that was good for a laugh!

I don't think the muck can be all that thick as the pond was renovated in late 2017, but I don't go to the bottom much. The sediments are probably a few inches thick as the aerator bases seem to be hard to pull up off the bottom, but sediments and muck, in my book, are two different things.

You may want to sample the bottom of your pond to see what is happening down there. Is it sediment or muck and how deep? If it is muck, as your water becomes more clear, i.e. crawdad boil, you may want to put a diffuser on the bottom to create more aerobic conditions.

Since it was recently renovated, you'll have a good idea of your pond management practices the past 2 years by sampling the bottom.

QA, I am hoping some others chime in but your late afternoon surface readings seem (IMHO) to be indicating lower than they probably actually are. These readings of surface water should be near saturation IHMO (saturation would be about 8.4). Are you confident in the instrument's calibration?

With regard to muck, I don't think you have much ... if any ... though the mud may well be very soft and hydrated on bottom. My son found a crayfish on fishing trip about 3 weeks ago and took it home for his aquarium. Quite remarkable the clean up it has done in such a short amount of time even recycling fish waste. I would have never guessed they could make use of that kind of food but it has grown noticeably and has already molted. We have supplemented his diet with a very small chunk of hotdog every 2 or 3 days ... so he has had some meat too. I mention the crayfish shredding activity only to highlight that they effectively recycle detritus and thatmuck will be slow to accumulate because of them.

Thinning the crawdads appears to be making a big difference on your water clarity.

I'll contemplate how to get the sample, but I'm not sure what to look for other than the depth of the muck and how it smells. And, I am confident that my diffusers are circulating the water from top to bottom and getting what DO I have down there .

I have cross checked the DO Meter with my Chemtech vial test kit, on occasion, and my confidence level is high.

I will remove more craws next year, if necessary, to further improve clarity but for now I am happy with some improvement. The water tends to clear up in the winter months anyhow.

EDIT: for clarification, when I say surface DO I am talking about the top 6" as the meter that I use has a 5" head on it that must be moving in the water to get a good reading. I bob it up and down as close to the surface as I can which means it's reading somewhere in the upper 6 inches.

Oddly enough I have measured DO levels as high as 11ppm at the surface, but just 24" down it was 4.8ppm.

So, I have brought the aeration system up over the last week and is now running from 10pm to 9am and plan to bump it up another hour or two tonight for water checks tomorrow. They are calling for rain, maybe, today and tonight which the pond could use due to surface pollen floaties, but I'd just as soon it held off until after the water checks to keep another variable out of the mix.

I will check the DO tonight just because my curiosity with respect to the effects of the added aeration versus evening DO is eating at me.

Any more suggestions for my weekend's testing efforts?

Disclosure: I don't know squat about aeration.

Would there be a benefit to turn off aeration totally for a period to establish a baseline of how the pond is "naturally?" Possibly the same for any other inputs like feeding etc?

Crayfish can cause turbidity issues in fisheries which lack dense enough populations of apex predator fish to manage their populations. Are you experiencing turbidity issues? I have significant unwanted experience navigating this issue - let me know I will help in any manner possible.

That would be an interesting thing to try, but for the time being, I will trust that aeration is a good thing for my pond. The pond is suffering from heavy pollen and I am in the middle of a Optimal feed trial, so I don't want to turn either off right now. It will be cooling off more very soon which would normally call for more airtime, so I think I will test what more air does first and then turn off and test the DO trends later this fall. And, I will certainly run plenty of tests next spring before the diffusers are engaged.

My summer secchi readings where 11-13" all summer UNTIL I recently removed 150 crawdads: 4-5" long. Within a week the muddy looking waters cleared to 22-23" and has stayed there...so, I would say that the craws are mostly to blame. I plan to enter next season with a close eye on clarity and remove some more craws. I have done some throw netting and have only caught larger craws. I suspect my original stocked craws have grown out in front of my game-fish and need to be eaten down. Next year's clarity should be improved one way or another (trapped and/or foraged).



I am open to any and all suggestions...thank you!

Good, manual trapping helps reduce populations - well done. What are your fishery species again? General population dynamics of apex predators? Have you experienced general reduction in macrophytes/FA due to dense crayfish populations? My .25 ac pond had all vegetation and algae denuded due to crays - my BG and RES couldn't keep up with YOY and had far too many adults. Even a few SMB couldn't help the situation, had to drain, seine, and start over [4 times!].

QA are you concerned that low DO has killed some of your HSB?

I stocked 42 HSB, 500 HBG, & 90 RES. These went in the pond spring of 2018 after a full year of FHM explosions. Dynamics??? Not sure I understand the question, but here goes...The two HSB I caught earlier the this year were ~2 pounds and ~16" long. My catch records show that every time I have caught one, they have gained in size or were similar. I've not caught a runt HSB. The HBG tend to be in the 0.4 to 0.6 pound range. I have some recruitment, but the largest ones are less than 4 inches and most are in the 2 to 3" range with wavering populations of 1/2 inchers. I think the HSB are doing their job along with low recruitment. The craws are probably a predator of the YOY/eggs also. The RES have not been seen since stocking, but snail populations are low now. I have not seen any dead fish except a few, maybe 10, within a few days of stocking...mostly RES and two HSB...leaving 40 in the pond. I put in about 300 craws during the first two years. 90% of them were between 1 and 3" long. The remainder being up to 4".



The first two years had minor FA mats (5-10% surface coverage during the wort off the summer) that were mostly removed by me and water clarity trended during those summers around 18-24". The winters provided water clarity that got to 36". This last winter, I ran a shallow diffuser in one corner and the water stayed muddy with 12" clarity that remained throughout the summer until recently when the 150 craws were removed. Best I can tell, no other factors contributed to the turbidity improvement. FA was only in the upper few inches of the water this summer. Growing on grasses that leaned over into the pond, Water Hyacinth roots, and the dock edges. No floating mats were ever witnessed. FA has been absent for a month or better. I can only conclude that the turbidity reduced FA development, the craws kept the shoreline shallows cleaned up, and my freshly renovated pond is low in muck and nutrients.



I have Pickerel Weed, Arrowhead, Thalia Dealbata, Botswana Wonder, & Mud Plantain, growing in the absolute shallows which do not seem to be succumbing to crawdad feasts. The Arrowhead seems to become craw food once it dies back in the fall, but during the growing season, they leave it alone.

I'm not sure what you mean by..."my BG and RES couldn't keep up with YOY and had far too many adults.". Does this mean you had way too much recruitment?

Anyhow, Starting over 4 times is TRUE dedication...the goal must have been very important to you.



I do not believe I have lost any fish to low DO or anything for that matter. My assumption is that I still have all my stockers and I see minimal recruitment. Lately, when I feed, the HSB and HBG will eat for as long as I throw feed. The last two weeks I have been feeding for an hour a night and throw in 0.25 to 0.35 pounds of Optimal BG (and some Optimal trial feed which, so far, has been 4mm round pellets). My fish do not frenzy during feeding...they take their time and stay spread out. I have been wondering that lower DO levels may be the cause. Feeding in the morning is practically a "no show". The DO levels during this time tend to be between 4 and 5 throughout the water column (aeration mixes it all in), but at night (aeration off all day), the DO levels are more like 6 to 10 in the upper few feet.

All in all, I am very happy with my pond, but worry about increasing biomass and seemingly low DO levels. I have not culled any fish for the dinner table and would prefer not to until the HBG are in the one pound range.

I am trying to determine if my pond is better with aeration running at max levels (summer temp driven) or if leaving the water to stratify, stay clear in the upper water column and maintain a consistent algae bloom is better.

Basic questions that keep running through my mind is...Is it better to have good DO levels in the upper few feet OR weak DO levels throughout the water column? What more, if anything, can be done to help DO levels in my BOW?

This morning's DO checks proved that the upper 3 feet of water was at 4.3ppm throughout the range (Temp and PH was also very consistent from top to bottom). I have to assume that the entire water column is at that 4.3 level due to the air running all night. This evening, I expect to see higher DO levels at the upper few feet.

I was hoping that I would see better DO reading this morning as I have bumped the air run-time from 5 hours to 12 hours over the course of the week, but the 4.3 reading is where the AM readings have been (roughly) for the last 2-1/2 months. The one time it was considerably better (5.6ppm) was during 24/7 air run times following a surface scum outbreak.

QA,

I feel wholly inadequate on the aeration questions but I would like to give you something to think about that may help with DO.

In addition to thinning the crayfish as needed, consider adding some additional shredder type forage. Hyalella Azteca and PK shrimp. Beyond the forage, I think they would help to keep your water clearer. They will be more abundant if you continue thinning crayfish and they may actually inhibit some of the crayfish foraging activity in the sediment in that they are also crayfish prey. Having clearer water will help your DO and these shredders will help to reduce the amount of decaying matter returning the nutrients to solution. Deeper sunlight penetration will boost photosynthesis and water clarity will help predators find prey and home in on your fishing lures. Both the fishing and DO should improve by reducing turbidity.

Jps, I'll do some research on the Hyalella Azteca and PK shrimp and look forward to getting some. What I know about the PK shrimp tells me that they need some good hiding areas (the right habitat). I don't think my pond is conducive for them just yet...next to no shallows and what shallows are their are practically void of micro structure. Just the same, I will do more reading and work towards creating the right habitat.

Thanks for your advise, truly appreciated!

Here's some data from this weekend for contemplation. I invite all thoughts on the subject as I am very new to water DO/chemistry and could use all the help I can get. First off, nothing about my pond indicates that it's current DO conditions are bad. I think I can contribute the slow feeding habits of my fish to lower DO, but beside that, I don't see anything wrong. I have just read "somewhere" that my DO levels are of concern.

Aeration ran Friday night from 10pm to 9am.

DO levels Friday night at dusk were...

6.5 ppm at the surface,
5.2 ppm 1 foot down,
4.3 ppm 2 foot down,
4.1 ppm 3 foot down.

Sat Morning DO levels were 4.3 from the surface down to 3 feet.

Sat @ 1pm...

6.3 ppm at the surface,
5.5 ppm 1 foot down,
4.4 ppm 2 foot down,
4.4 ppm 3 foot down.

Sat @ 6pm

9.6 ppm at the surface,
6.5 ppm 1 foot down,
4.5 ppm 2 foot down,
3.8 ppm 3 foot down.

Saturday was overcast 95% of the day with a slight breeze at the pond.

pH ranged from 6.3 to 7.4 depending on time and depth.

Water temps were 76 to 79 depending on time and depth.

Ammonia, Nitrates, and phosphates were all Zero all day.

My question still stands...Is it better to have good DO levels in the upper few feet OR weak DO levels throughout the water column?

Just curious, how far off the bottom are your aerators? My guess is your aerators are a few feet off the bottom.

3 foot off the bottom... One in 10 foot of water, the other two in 6-7 foot of water.

If you have your reasons, then disregard the free advice...

Aerators are generally poor at adding oxygen to water. Roughly, 1.5% of the oxygen diffused is dissolved in the water for every foot of depth. When it comes to diffusers, deeper is usually better.

Also, since your diffusers are 3 feet off the bottom, your bottom is stratified and anaerobic.

Unless you have your reasons, it may be worth experimenting with the diffusers at the bottom of the deepest part of your pond. Note of caution, depending upon how stratified your bottom has become, harmful gasses could be released when you first begin true bottom aeration.

Experimenting with the depth of the diffusers may come into play next year if the water continues to clear. They started at 18 inches off the bottom and were moved up to 3' to help with clearing the water. That did not have the effect I was hoping for. Removing crawdads seemed to be the ticket, so the diffusers may go back deeper.

With that said, I do not get a thermocline or stratification with my setup even with the diffusers set to high. I believe, equal temperature readings from top to bottom prove that. After the aeration has run, the temps are within 1 degree which indicates thorough turning of the pond. After the aeration has been off for 10 hours, the only sizable temp difference is at the upper foot of water which can be 10 degrees during the heat of the summer.

Maybe if I could run the aeration 24/7 there would be improvements, but Midwest summers dictate nighttime runs in my small pond. This has me scratching my head regarding the DO readings that I get. With cooler weather approaching I hope to get the aeration system up to near 24/7 and look forward to the resulting DO checks.

My fear is...with the air system on full time, it thwarts the benefits from the O2 producing algae blooms by turning them to the depths of the pond where they can't get good sunlight. Of course, I have no scientific proof that there are algae blooms present other than the green color of the water where it used to be more brown from crawdad mud stirring.

what is a good D.O. meter probe that y'all would recommend?

thanks

I am reviving this thread from last year as I am still concerned with the DO in my pond. I am still finding that the DO levels from 6" at the surface to 36" down after the aeration stops in the am to be low (3 to 4ppm). The evening readings are...

________Surface (@6")____24" down______36" down
DO______ 6.2____________3.5____________2.3
PH______ 8.1____________7.8____________7.7
Temp_____82 F___________71____________69

I have calibrated my DO meter with 7.0 PH buffer solution and it calibrates the DO level off of the outside air oxygen content...so it should be working correctly. Last year I cross checked the meter with a vial-type DO test kit and it matches. I believe my readings to be good, but I am going to do some research on the instrument and double check my methods of calibration.

My well water reads...DO = 3.9, and PH = 7.7. My fish might be better off in my well. LOL

The massive amounts of bullfrog tadpoles are visibly absent in the am, but swarm the surface gulping at the surface in the evening. I never see fish piping at the surface. I threw a 7-8' net yesterday for 40 minutes off the dock and removed over 400 tadpoles (into the creek - my wife asked if I counted...of course I did). I averaged 20 TP's per throw with a max catch of 40 in one throw. Right, wrong, or indifferent...I think that removing biomass will help. I will remove more TP's today along with trapping out more crawdads to help improve water clarity. I caught only a few 2" HBG young during the netting process BTW.

I only run the air at night to avoid heating the pond and have thought about running it 24/7 to help with DO, but 3-4ppm readings after it shuts off does not encourage me much.


Anyone out there have DO readings to compare with respect to air run times and such?


Anybody have any advise to offer?

QA - Here are some thoughts just from high level. You aren't running 24/7 to avoid raising the temp to a level that stresses fish. However, if the DO gets much lower you possibly risk fish dying. I think bump up the run time and gather more data. It really seems like the only short term option to me. Long term option - what about installing a bigger pump to get even more turns per run time? It would seem that if you exposed the water to atmosphere even more it would have no choice but to absorb more O2. If you could do that in the same run time you are doing now then you shouldn't have to worry about temp.

I hear you WB! Thanks for the thoughts, we are thinking along the same lines.

I just added 2 more hours to the run-time last night for a total of 9 hours (dusk to dawn). I estimate that I am, now, turning the pond over 3 times at night while the air is running. Foregoing the rule of thumb regarding at least one turnover per day, my pond does not seem to adhere to this rule...I plan to monitor the DO and keep increasing run-times until temps get up there. We'll see what that does. I have room to extend the run-times further into the morning hours, but summer heat is coming. I have removed 100 crawdads in the past few days which should reduce turbidity. Not to mention, it's pollen-water floaty-surface scum season and the water's surface is looking a bit "thick". With all these variables changing...who knows the real causes and effects? So long as DO goes up...I don't have the luxury of caring.

Just for record keeping and ease of comparisons...the last two nights readings (after re-calibrating the DO meter strictly to the the instructions)...

6/2 (5pm)...

________Surface (@6")____24" down______36" down
DO______ 6.2____________3.5____________2.3
PH______ 8.1____________7.8____________7.7
Temp_____82 F___________71____________69

6/3 (5pm)...

Secchi = 11"

________Surface (@6")____24" down______36" down
DO______ 6.0____________5.0____________2.6
PH______ 8.0____________7.8____________7.7
Temp_____82 F___________75____________70.1 (EDIT - I had typo'd in 60 instead of 70 - my bad)

Wow, those are huge DO gains at 24" and 36" at the cost of a small amount at 6".

Since I love crunching numbers...

You gained 42.8% more DO at 24".
You gained 13% more DO at 36".
You lost 3.2% DO at 6".

QA,


A series of measurements starting in the morning (like 6 am - 10 am) might help tell you how long to extend your run. The O2 level won't shoot up when the sun hits but takes a while to get up there as the plants produce it.

Also, is there an expert comment on the thermocline QA is showing? Is that a sign of inadequate mixing?

Interestingly Bob Lusk just made a post saying that fish WILL choose favorable Temp over DO. That is kind of counter intuitive, at least to me.

Quick DO checks last week around 8am were consistent at 3-4ppm top to 36" down. The aeration system kills the upper DO levels, but improves the lower and makes it all poor IMO. I will be increasing the run-times an hour or so a day as loger run-times helped last fall once the summer temps faded. I'll be watching DO this weekend pretty close.

I think he thermocline you may have thought you saw in my data was a typo...I had a 60.1 instead of a 70.1 (it's been corrected - sorry and thanks for bringing it to my attention). Otherwise, the true delta T's are pretty typical at the end of the day when air shuts off in the morning.


I saw that and thought that my fish must really hate 75 to 82 degree water more than DO in the 2's.

QA, I hope you don't mind me jumping in here but your post about whether to aerate or not along with Bob Lusk comments about water temps verses DO has me questioning where to go with my existing aeration system. Do I want cooler water or higher DO numbers. I have been searching for a leak in my 1800' of air line along with rebuilding two pumps has kept my aeration shut down so far this year. I'm still working on solving the problem of not enough air to run the six diffuser system. After 4 yrs of aeration experience at my pond, I continue to questioning myself on how to keep my water temps down and DO up during our hot summers temps? Even after I fix my aeration system, I may just leave it off this summer just to see what I can see. My fish seem to have survived my 92 to 87 degree water temps over the past summers using aeration with no thermocline. How will they do without aeration but cooler water temps may be answered this summer.

Jump in Tracy, the water is fine (maybe??? lol). The more the merrier. I'm not ready to shut my aeration off for the sake of experimentation, but you have found yourself in a situation that may lend itself to that test. Keep us updated on the results.

Readings where taken again yesterday and I think I will continue to regurgitate the previous readings for ease of comparison. Air run-time has been extended by an hour or so every night since the first reading was taken and we received 2 inches of rain this morning, so, who knows what that will do to this evenings readings. Typically, my rain runoff into the pond has DO levels around 6. The 12" drain pipe had about 3 inches of running water at the intake...it got a decent flushing. The pollen floaties (or whatever it is) was getting pretty bad. This rain will make the surface appearance much better and, I predict, make the turbidity worse. I'll see this evening.

6/2 (5pm)...

________Surface (@6")____24" down______36" down
DO______ 6.2____________3.5____________2.3
PH______ 8.1____________7.8____________7.7
Temp_____82 F___________71____________69

6/3 (5pm)...

Secchi = 11"

________Surface (@6")____24" down______36" down
DO______ 6.0____________5.0____________2.6
PH______ 8.0____________7.8____________7.7
Temp_____82 F___________75____________70.1

6/4 (5pm)...

Secchi = 10"

________Surface (@6")____24" down______36" down
DO______ 6.8____________3.5____________2.5
PH______ 8.2____________7.9____________7.8
Temp_____84 F___________73____________71.1

Steve - -thanks for running some numbers. I must say that the DO numbers are tricky to get as the meter requires that the probe be moving 6" per second in order to read accurately. That is difficult to do in the pond and the display is constantly moving slightly, but not so much that I cannot get a mental running average. I would not put too much emphasis on the DO percentages. The ppm readings could be off by a couple of tenths.

I'll get more meaningful data this weekend when I can get a few sets a day (morning, mid, & evening).

These temps have me perplexed.

I'm running mine ~10hrs - 9:00pm-ish til 7:00am-ish, depending on when I start/stop the pump.

Last couple late afternoon temp checks I've done have been ~75° on top and ~70° 10' down.

You're seeing ~12° delta in the top three feet.

Are you sure that your air pump is pumping the amount of air that it's supposed to be pumping?

Are those numbers saying that maybe it isn't?

I don't know, but it seems odd given the similarities and proximity of our ponds.

These temps were taken 12 hours after aeration was turned off. - giving it time to stratify a little??? I am going to bet that the temps are very consistent below the 36" to the bottom. I will look over the pump this weekend while running, but I think all is good with the pump. It's not uncommon for my pond to have a good delta T between the very surface and a foot or so down, long after the air turns off. The water temps have been very consistent from top to bottom at the end of the air run-time, indicating good turn overs.

IIRC your pond is deeper than mine. Mine is 10 foot and your water is much more clear. Does muddy water heat up more at the surface??? My pond also receives very little wind action. I'm just thinking of the differences that may come into play.

Keep an eye on me Augie! I will get more temps checks and such this weekend and maybe it will paint a more thorough picture.

I'll check mine again in a day or two. Got ~5" of new water overnight so not much point checking it today.

The water in mine hasn't cleared to anywhere near like what it was when you saw it last summer. Last summer it was pushing 6'. Right now it's more like 3'.

The mudbugs I got from you are down there working hard, which is a good thing. I've been finding dozens of 1"-1.5" baby crays every time I rake FA.

Clear water is really pretty to look at, but the dang snotgrass goes crazy when it gets too clear, so in my case the reduction in visibility is welcomed.

Good to here the craws took. I am looking forward to running checks this evening JUST to see what the rain event did to the water.

I know your data isn't enough to make a sweeping conclusion about aeration, but it's got me wondering if I want to eventually aerate my pond. Going by what Mr. Lusk said, would it be reasonable to conclude, that if you're meeting the bare minimum DO for the species you have without aeration, that aeration isn't required? By not aerating, you're keeping favorable temperatures, which are apparently what fish prefer over water that has more DO than they need.

Some interesting stuff here.

Aeration has other benefits beyond just additional O2 for fish respiration. It allows aerobic decay of organic matter, which is much faster.

I have been a fan of aeriation for the past 4 yrs but at my place in the hottest part of the summer July, Aug the water temps are just to high when aeration is running whether it is early morning run or a night run. I don't have a deep pond and was designed to be 12' in one deeper pools and 10' in another pool section of the pond. But in the hot summer months the pond will be shallower due to evaporation. This also comes into play when aerating at my place. I see the benefits of diffused air but I have also seen the negative side of it. I have been listening to Bob Lusk the past couple of years when he speaks of cool water refuge during the hot water season. His comments has influenced my thinking and I have made several changes when it comes to diffused air but nothing I have done so far gives me a cool water refuge. I am still looking at it all.

I'm with you Tracy, I have never achieved a thermocline in my 1/4 acre pond with the air running. I have lost faith that it can be achieved in a small BOW, AND still maintain good turn-overs. My three diffusers are 3 feet off the bottom and spread out evenly in the dam side half of the pond. I could move them higher in the water column, but then the lift rate diminishes and my run-times would need to approach 24 hours a day. Maybe this would be better, but I don't think so, hence not putting in the effort to raise the diffusers (again).


This is were the thread title comes from..."To Aerate OR Not to Aerate". In my case, I am hoping to maximize my little puddle and that is why I have air in it. That and I like to tinker. I believe that aeration should help do that, but the trick in warmer climates is to balance it with the water temps. The one piece of info that I am really missing is...what constitutes dangerous DO levels? I assume that I am pushing that limit, but I really don't know. Bob says "They really can't judge the difference between 3.5 ppm or 6.5 ppm." in this thread...

https://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=522102#Post522102

This make s me think that 3.5 ppm is not so bad, but I don't want to take it out if it's original context.

IMO, a pond without air will balance itself. Meaning that once the biomass meets the available DO levels fish will start to suffer in one way or another. This suffering can be in the form of lack of growth, increased illness, or, during an extreme event, a fish kill. An aerated pond allows for more biomass (given that it is done properly and adds DO to the pond), but when the hot summer starts to push the temp limits the aeration must be cut back. This improves the chances of that extreme event. IMO.

EDIT: Added yesterday's data...........................................................................................................

I grabbed some more readings yesterday to compare to the earlier weeks data...

6/2 (5pm)...

________Surface (@6")____24" down______36" down
DO______ 6.2____________3.5____________2.3
PH______ 8.1____________7.8____________7.7
Temp_____82 F___________71____________69

6/3 (5pm)...

Secchi = 11"

________Surface (@6")____24" down______36" down
DO______ 6.0____________5.0____________2.6
PH______ 8.0____________7.8____________7.7
Temp_____82 F___________75____________70.1

6/4 (5pm)...

Secchi = 10"

________Surface (@6")____24" down______36" down
DO______ 6.8____________3.5____________2.5
PH______ 8.2____________7.9____________7.8
Temp_____84 F___________73____________71.1

6/5 (5pm)...

Secchi = 10"

________Surface (@6")____24" down______36" down
DO______ 7.3____________4.1____________3.1
PH______ 8.5____________8.0____________7.7
Temp_____84 F___________73____________71.5_____At the very bottom = 70.7

Secchi = 10"

We had 2" of rain yesterday morning and received a good inflow (and out). In the past, the rain water inflow had DO levels at 7ppm. The air run-time was increased the night before by an hour or so. It's hard to tell what the exact reason for the slightly increased DO is, but I think increasing the run-times is helping so I will continue until the water temps get high.

125 crawdads have been removed this last week with and additional 15 about a month ago. I'm looking for improved water clarity. Yesterdays rains did not make it worse, so that's good.

I see where your visibility is at or around 10". Is that due to plankton bloom or suspended clay? When I had the bloom keeping my visibility @ 10" I was concerned/worried to the point I added Alum/lime to clear things up.
And I have too much vegetation due to the water clearing. Plankton, like vegetation also effects the DO. One thing I have noticed this year is my water temps are quite a bit cooler, I think it's because of shading due to plants.

I am pretty sure the low visibility is due to both clays and blooms. What kind of blooms, I can not say. The pond is trying to surface scum-up on me right know. The oily looking film that turned into serious scum floaties last year. Here's a pic of the water, the grey bucket is about 4-5" under water. A jar test shows that it clears up well within a week or so...I'm thinking clay and blooms...This photo was taken before the surface scum appearaance.

I was able to get multiple readings this weekend for evaluation. Aeration was set to run 8:30pm to 10:30am the night before and left there all weekend for the following data points. The two days were very sunny and peaked in the low 90's (hot and humid).

6/6 ________6"deep_____24"_____36"_____7 foot deep (at the bottom by the dock)

(6am) DO____2.7________2.7_____2.6______N/A
(12pm)DO___3.5________2.9_____2.8_______N/A
(5pm) DO___7.0_________2.4_____2.3______N/A

(6am)Temp___74 F______74_____74_______73
(12pm)Temp__84________74_____73________73
(5pm) Temp__87_________75_____74_______73

6/7 ________6"deep_____24"_____36"_____7 foot deep (at the bottom by the dock)

(6am) DO____2.9________2.9_____2.9______N/A
(12pm)DO___4.2________3.2_____2.9_______N/A
(5pm) DO___8.2_________3.2_____2.9______N/A

(6am)Temp___74 F______74_____74_______74
(12pm)Temp__83________76_____75________75
(5pm) Temp__88_________77_____75_______75

Secchi readings hovered at the 10-11" visibility the whole time and PH readings were consistent in the morning from top to bottom around the 7.5 to 8 range which changed as the day grew long landing at the low 8's at the surface to the mid 7's at 36" down.

The only conclusions I can draw from this is that the daytime hours really boost the uppermost DO levels along with rising temps while the aeration mixes is all back in at night to yield lower DO levels throughout the water column along with consistent temps top to bottom. I have to admit...I don't know what to think of the data beyond that. I suppose I will continue running the air "as is" until temps get obnoxious and then consider shutting the air off completely (gradually) and then get more readings to see what happens without air.

I am open to comments and advise (as usual)!

So I have a few questions, and forgive my ignorance on the subject. Is the reason that a pond's temp increases with aeration related to the outside air temperature of the location of the compressor? (i.e. If your compressor is outside in 90-degree air, it's sending 90-degree air into the water, which is what causes the water to heat up.) If yes, would the opposite also be true, if the compressor is in a climate-controlled room, which could potentially send cooler air into the water?

The water tends to heat up due the the added exposure to the sun and ambient air temps. This is because the water is constantly being turned over bringing cooler water up and allowing it to "soak up" the heat. Eventually, you heat up the entire column of water. Some heating occurs due to the hot compressor air, but I am betting its negligible compared to the power of the sun and air temps.

Ahh, thank you for the explanation. I'd be interested to see what would happen if you aerated your pond with a compressor sitting in a refrigerated (LOL) room. For science!

Some "fun" numbers to throw around while we're being scientific....If you had a 2.5 ton chiller (specifically made to cool water and about the same BTU or ton rating as a 1300 square foot home's AC unit) and a 5 gallon per minute pump...it would take 1700 hours to cool the pond down 10 degrees (about 70 days). This won't work in my neck of the woods.

In a more real sense, I can see how a 500,000 gallon pond (~ 1/4 acre) with aeration could easily be fighting a 1 degree increase per day as summer heat escalates. That chiller system would need to remove 1 degree per every one of the half million gallons per day. In order to do this, you would need to pump every gallon of the in a 24 hour period...that's a 350 GPM pump. The tonage on the chiller unit would need to be about 17 tons. Just to give an idea of how big that is...A 3000 square foot home requires a 5 ton unit. AND, the pump is massive, in the neighborhood of a 10 HP motor. AND, we are talking about a chiller system that is designed to chill water as efficient as possible. The introduction of cool air from an air-conditioned room into an air pump would be pretty efficient aside form the fact that the AC room air would have to overcome the heat generated by the air pump first, but the efficiency of the air bubbles cooling the water off would be horribly in-efficient.

Disclaimer: I have made some very crude assumptions in the above mumbo-jumbo and could certainly be off by a fair piece, but regardless...It would take a lot of equipment to keep a pond cool during the heat of the summer in the warmer climates.

Thanks for the diversion Steve_! Back to your regularly scheduled program...

QA what are your night time low temps around there?

The last week or so has had lows near 70 F and highs in the mid to upper 80's and low 90's

No problem! It's interesting to see the numbers, but if you're comparing what it takes to cool air against what it takes to cool water, I think the numbers would be slightly off. It does take more energy to cool the water, but it also holds temperature better than air.

Side question, do you have any trees or shade around your pond, or does it get direct sunlight most of the day?

The pond has morning and evening shade. It starts getting direct sunlight around 9:30am and starts losing it at 4:30pm.

As far as the heat transfer calcs...the estimates for tonage sizes we're for water chillers, but the comparisons to AC units may not be apples and apples. Good point!

So I'm just going back to my initial line of thinking. Theoretically speaking, if you could turn your pond over 2-3x while the temp was 70F you could lower the ponds temp. Why not just upsize the pump and turn it over as many times as possible at night??

I know your onto the solution to better temps and better DO WB with a larger system. My aeration system is currently turning over the pond almost 5 times during the 8:30pm to 10:30am schedule. I believe this is contributing to the turbidity issues. I can get more turn-overs by lowering the 3 diffusers to a foot off the bottom, but, again, turbidity. If I drop the diffusers to the bottom, I estimate that I can turn the pond over about 7 times in the current 14 hour run-time. So, I'm in a pickle I guess. My goal is to get between 24 and 36" visibility with good DO levels and to understand my pond more. My pond is throwing the "one turn-over per day rule of thumb" back in my face even at near 5 times at night. Do I need to actually hit the one turn-over per day rather than exceed it? Maybe?

I am working on taking crawdads out to reduce the muddy waters, but don't want to eliminate them. Once I get some clarity, maybe I'll start dropping the diffusers back down for more water movement.

Spawning activity can also be a significant contributor to turbidity.

BUT, there is a thing called evaporation cooling. So, depending on the humidity reading in the ambient air, wouldn't aerating also possibly cool the pond as the air that is pushed to the bottom of the pond absorbs moisture from the pond on it's way to the surface?

QA, have you tried the jar test to see if the clay turbidity is due to electrical inbalance or mechanical means? If you had a denser phytoplankton bloom (18" -24" visibility and none of that due to clay turbidity) I think your O2 levels would be higher in the daytime and therefore when you ran the aerator at night you would have higher O2 levels overall than what you have now.

I would be interested to see what the O2 levels (and temp levels) would be if you ran the system 24/7 for a week. If you felt the water was getting too warm you could shut the system off and the water at the bottom of the pond would start cooling off pretty quickly due to the cooler soil temps surrounding the pond.

Not that I have done any testing on the subject, but my gut tells me that any cooling from evaporation is over taken considerably by the radiant heat from the sun and the convection heat from the ambient air at the water-to-air interface. Evaporative cooling works best in very low humidity areas and the surface of a pond would not be considered low humidity especially not in my neck of the woods.


It's been a while since I performed a Jar test. This was from last year with a clarity of 18"...





If it is suspended clay...it's may just have to "be what it be". I will not be treating my pond with alum (etc). I get too much water throughput to spend the time and money on chemicals. One good rain and I have just treated the creek. I would like to hear more about electrical imbalances however. That sounds interesting! I am having a hard time understanding how a BOW that is SO connected to the earth could have an electrical imbalance...seems like a pond would be about as grounded as anything could be.


I have not done this, but have wondered the same thing. Maybe I will try this later in late summer early fall. I do recall trying to run the air 24/7 early on and found the water temps to climb above 85 and had to back off the runtimes.

QA - I believe what he is referring to is the electrical charge of the tiny plate-shaped clay particles that prevent them from settling. The alum atoms have the opposite charge which allows the clay/alum to bind together such that they are dense enough to settle to the bottom. see https://wkrec.ca.uky.edu/files/muddyponds.pdf That treated clay is therefore "forever" treated and will re-settle if stirred, but you need to prevent additional untreated clay from washing into your pond. Or untreated clay on the bottom from being stirred up. "Unused" alum does not stay suspended in the water column from what I understand - it sinks to the bottom.

I treated my pond with alum about 3 months ago and have been very happy with the results thus far. Secchi readings went from 8" to 36" that afternoon. Its a pleasure to see bluegill and bass cruising around. Last week I got 5" rain but all is still good.

Since you get some (most?) of the clay settling in your jars, it appears part (majority?) of your problem is mechanical action of crawfish, bullheads, tadpoles, aeration, etc.

After clearing up the water and having 30" of visibility you need to keep a close eye on the vegetation growth. Vegetation can grow out of control real fast once the clear water allows the sunlight to hit the ponds bottom. Identify the plants that start up making sure you know what it is and how to control it. If you don't have grass carp then I suggest you get some as soon as possible after clearing up the water.

Tracy, you probably mentioned it earlier but I forgot: did you stock extra crawfish this year? If not, do you think they might have helped control the vegetation a bit? I have some naturally, but maybe could add more next spring if the world gets a little more sane.

Red, I'm pretty dumb with respect to clearing the water with Alum, so my fear is that I would clear the pond in April/May time frame and a gully washer would put the mud back into the water column...I'm guessing my efforts would be in vain. My little 1/4 acre pond has an excess of 20 acres of watershed and can get flushed with just a few inches of rain...we got 2 inches last night and that sent water through the pipe when it was down 3 inches yesterday.

Tracy and ant, should I ever clear the water with Alum...my crawdad population MIGHT thin out enough to grow some veggies. Maybe the fish could see them better. A carp would starve to death in my pond right now.

I had almost perfect fertilized water for about 3 1/2 yrs And then visibility went to 9" vis. of fertile water. I also had a problem with aeration disturbing up detritus on the ponds bottom which contributed to the low visibility. I raised the diffusers off bottom. I decided to add alum/lime treatment. At that time I had some American pondweed along the shoreline. Water cleared to 36" and shortly after that the Bushy pondweed showed up along the edges of the APW. That was in the fall. I added 3 Grass carp per acre. The water cleared even more that winter with 8 to 10' foot of visibility. The following spring the BPW was growing all over the pond to the point it covered 70% of the pond. I added another 5 grass carp making a total of 5 per acre. All the vegetation caused low DO and a fish kill. I will wait till the water cools down and start fishing again and see what I have left.

Frank, I do have crawfish. I see them along the ponds shoreline and when raking the matts I find some in the mat. I believe I would have to have a commercial crawfish pond if I wanted to have stopped the bushy pondweed. And even that may not work. I feel like the feeding of the fish over a five year period contributed to the vegetation growth through high nutrient water, along with the clear water. It made the perfect storm!

I feel like this has set my goals for the pond back at least 3 yrs.