Pond Boss Forums AERATION Systems questions Oxygen readings. What next?

Yes, aerators and lower feeding completely wiped out the algae. However, I got in my oxygen probe so I wanted to get an idea of the levels at the pond. See the pond pic and the readings. I was not expecting so low readings at 8’+ Note, my probe is only 10ft max. Temp yesterday over 95 and no rain in weeks.



A1: Aerator diffuser 1
A2: Aerator diffuser 2

Main top spring: 1’ - 4.85mg/L - 69F

T1 Site: 2’ - 11.34mg/L - 85F

T2 Site: 2’ - 12.34mg/L - 87.6F
T2 Site: 4’ - 11.15mg/L - 87F
T2 Site: 6’ - 10.24mg/L - 86F
T2 Site: 8’ - 6.57mg/L - 84.9F
T2 Site: 10’ - 0.08mg/L - 84F

Took another reading 3ft away from A2 @ 9ft = 1.7mg/L - 82.5F

I’m using 5.7cfm compressor with bottom diffusers. Seem’s to be kicking of plenty but I’m stunned by the drop to 0 when I get to 8’+. Should I move both diffusers to deepest sections? I’m not getting any foul smell. They’ve been running for a few weeks now 24/7. I was concerned about having most diffusion so close to the spillway. That is why I have one up in the shallow by the spring. Thoughts?

Those are pretty good readings, makes sense that the DO is low below 8 feet, what time of day did you take the readings? Try taking some at night as well.

I wouldn't put the diffuser on the bottom - with DO that low you could force a fish kill, check youtube for that exact same scenario..

I think you might have similar results with no aeration but that is just me, my lake is the same size and depth and I have no aeration, similar DO results. Honestly dont over think it, your fish are super healthy from what you have said so other than water clarity and algae which you have started to clear up why bother throwing a wrench into the mix.

Check out my recent post on riparian/hyporheic zones, that might make a difference for you was well.

Cheers.

As you are finding out, there is more to a bottom diffusion aeration system than just putting something in the pond to make bubbles come up to the surface.

Can you answer the following questions?

How many gallons of water does each diffuser bring up to the surface of the pond per hour of run time? That number will change according to the depth that it is placed.

How many CFM does your compressor put out at 6 psi backpressure?

Let me clear up some misunderstanding.

1) The goal of a bottom diffusion aeration system is to bring O2 to the bottom of the pond, so the fish have the whole water column to utilize, AND bringing O2 to the bottom of the pond will allow aerobic bacteria to colonize the organic matter at the bottom, which in turn will greatly reduce the amount of annual muck accumulation.

2) Placing the diffusers on the bottom in the deepest part of the pond is exactly how a system is supposed to be installed.

3) A properly designed and installed bottom aeration system will show minimal water temp change from top to bottom, and will also show minimal O2 differences from top to bottom. That is the purpose of a bottom diffusion aeration system.

4) When installing a bottom diffusion aeration system in a pond that has a thermocline set up, with a very low DO reading at the bottom, it is critical to use the correct start-up procedure to prevent a fish kill. You WILL kill the fish in the pond if you just turn the system on and walk away. It's not the low O2 water that is killing the fish, it's the H2S gas that is killing the fish.

Let me clear up some misunderstanding.

1) The goal of a bottom diffusion aeration system is to bring O2 to the bottom of the pond, so the fish have the whole water column to utilize, AND bringing O2 to the bottom of the pond will allow aerobic bacteria to colonize the organic matter at the bottom, which in turn will greatly reduce the amount of annual muck accumulation.

2) Placing the diffusers on the bottom in the deepest part of the pond is exactly how a system is supposed to be installed.

3) A properly designed and installed bottom aeration system will show minimal water temp change from top to bottom, and will also show minimal O2 differences from top to bottom. That is the purpose of a bottom diffusion aeration system.

4) When installing a bottom diffusion aeration system in a pond that has a thermocline set up, with a very low DO reading at the bottom, it is critical to use the correct start-up procedure to prevent a fish kill. You WILL kill the fish in the pond if you just turn the system on and walk away. It's not the low O2 water that is killing the fish, it's the H2S gas that is killing the fish.[/quote]

OK sorry let me clear up clear up the muddied waters as they say. I dont disagree with anything you are saying, but I dont believe that just because a hole has water in it there should be an aeration system. From his description, pics, and video that is a healthy ecosystem that in my opinion the only real issue is the excessive feeding...but i get why because he wants big BG. Those water temps and DO numbers are the same as mine in my BOW and everything is just as healthy but I dont feed my fish. I understand we are very far from each other but the water temps are the same.

To equalize the water temps and DO in his lake in my opinion is not needed, why do they need to utilize the entire water column when the waters they are inhabiting provide everything they need? BG survive in waters down to 1ppm, same as my PS's and my trout have made it in that low as well although they are stressed. He doesnt have trout but i'd recommend that anyone with trout not mix that water up or they will lose them for sure.

I also think that his lake is different than many others in the hotter states - it is spring fed and isnt showing signs of stress other than the algae from excessive nutrient load. Im pretty sure he also said that he only started aerating recently.

What I would do is since the lake is recovering by lowering the feeding and keeping the aeration, I'd try removing the aeration for a couple of days to see how the algae responds, and then stop feeding and leave the aerators on to see what happens - a few days should tell the story although it might be overloaded with excessive fish food already. but before doing that check the DO levels first thing in the morning as a baseline and then manipulate the system and check again. I also mentioned cascading the little water input as Im pretty sure it will help.

The only other thing not addressed is aerating the muck at the bottom, in his ecosystem Im not sure it is really needed, it is much different than most man made ponds/lakes. I would focus on letting it be a natural system that can sustain itself, just catch and eat some bluegill from time to time to deal with the carrying capacity of the lake. He can also snorkel it to check the quality of the water and see what the bottom is like.

The other thing I would do tend to the shoreline to develop the riparian areas, this might relieve some of the nutrient overload and help with the algae, and would probably do so within a short year or two to start.

We have many natural lakes in our area that are basically the same as his and mine that support natural fish and have for decades with no aeration, spring fed and shallow, little beauties.

I have aerated in the winter to keep my ice open for my trout but Ill have inflow/outflow this winter so I wont be aerating.

Cheers.

Well pretty confused but then again this is all new to me. I have no idea how much water they're currently moving. It's being powered by a 5.8 CFM 3/4 horsepower compressor. I can say that it bubbles quite a bit at top I mean it creates about 3in boil over at least vertically and seems to be moving quite a bit of water. I restricted aerator 1 since it's closer to the compressor to put off what visually looks like the same amount of air. Again, aerator 2 is in what would be the deep area. I guess I could move aerator 1 over there as well. They've been running 24/7 for over 3 weeks maybe a month and I get no foul smell but yet they're obviously is no change in the water that's 8 ft Plus.

I might stay out there overnight tonight and if I do I'll take a reading in the morning before I go to work and see if those readings are different then during the middle of the day. I understand that I could turn them off and see about any algae change but since that's under control my current goal is to accomplish a more uniform oxygen system. From what I understand, which is not much, the benefits are that the body of water can maintain more fish, reduces potential fish kills, helps with freezing over the winter which I don't really need because the springs keep two sections from freezing, and overall increases the temperature of the body of water which I would like because like I said due to the spring it is generally a cooler pond for swimming.

What if I added a diffuser to the top spring as water comes in would it stay oxygenated or diffusers, that are working adequately, at the deepest parts be the best option?

I wear a farmer john wet suit when I snorkel my lake because it's cold, during the day you'll literally see the bubbles flowing off the vegetation under the water, photosynthesis from plants and algae etc creat the oxygen. You'll get some diffusion at the surface from the aerators as well but I'd be interested in seeing what you get with and without them. Like you said before the fish were fine before the aerators?

Yeah truth is fish were doing really well before the aerators but I had such bad algae in July. I started looking for solutions and when the aerators did not work I deduced, with the help of people on here, that I was overfeeding them this Summer. When I cut the food back algae disappeared. How much the aerators had to do with that I don't know but now that I have no algae I was hoping the aerators would oxygenate the pond better for the benefits that I've read about oxygenation in a pond. Problem is within 5 ft of the aerator that's in the deepest part of the pond I get zero reading past 8 ft deep

Ill check my DO tomorrow and take pics so we can compare. I have LMB, pumpkinseed sunfish, rainbow trout and brook trout.

Louie

Took readings again this morning at 7:30am When i left i slowed the outflow to A1 down to a minimum, increasing the outflow to A2 since its in the deepest section. I'll be back out there in a week to see if that makes any difference. Here are the readings for this morning. Still little to no DO past 8' And, the other readings are near half of during the day. Is that normal?


Main top spring: 1’ - 3.07mg/L - 65F

T1 Site: 2’ - 6.43mg/L - 79.1F

T2 Site: 2’ - 6.75mg/L - 82.9F
T2 Site: 4’ - 6.04mg/L - 83.1F
T2 Site: 6’ - 5.33mg/L - 83.6F
T2 Site: 8’ - 6.44mg/L - 84.2F
T2 Site: 10’ - 0.58mg/L - 83F

Yes that's normal from when I've recorded here in the past. There are times late winter I have 40 inches of ice Ian's 2ppm and they make it here ...stressed but make it

OK sorry let me clear up clear up the muddied waters as they say. I dont disagree with anything you are saying, but I dont believe that just because a hole has water in it there should be an aeration system. That is 100% correct.Different waters and different goals. From his description, pics, and video that is a healthy ecosystem that in my opinion the only real issue is the excessive feeding...but i get why because he wants big BG. Those water temps and DO numbers are the same as mine in my BOW and everything is just as healthy but I dont feed my fish. I understand we are very far from each other but the water temps are the same.

To equalize the water temps and DO in his lake in my opinion is not needed, why do they need to utilize the entire water column when the waters they are inhabiting provide everything they need? Because as the fish grow, unless he starts an intensive harvest plan, he will have more pounds of fish in the same gallons of water. Allowing the fish to utilize the whole water column reduces the pounds of fish per gallon. BG survive in waters down to 1ppm, same as my PS's and my trout have made it in that low as well although they are stressed. He doesn't have trout but i'd recommend that anyone with trout not mix that water up or they will lose them for sure. You are correct in not mixing the water if you have trout. In his situation though, you do realize that there is a difference between just surviving and thriving, correct? To grow big fish they have to thrive every day of their life, not just 25% of it.

I also think that his lake is different than many others in the hotter states - it is spring fed and isnt showing signs of stress other than the algae from excessive nutrient load. Im pretty sure he also said that he only started aerating recently. The older the pond gets, the more nutrient load that it will have. Look at

What I would do is since the lake is recovering by lowering the feeding and keeping the aeration, I'd try removing the aeration for a couple of days to see how the algae responds, and then stop feeding and leave the aerators on to see what happens - a few days should tell the story although it might be overloaded with excessive fish food already. but before doing that check the DO levels first thing in the morning as a baseline and then manipulate the system and check again. I also mentioned cascading the little water input as Im pretty sure it will help.

The only other thing not addressed is aerating the muck at the bottom, in his ecosystem Im not sure it is really needed, it is much different than most man made ponds/lakes. I would focus on letting it be a natural system that can sustain itself, just catch and eat some bluegill from time to time to deal with the carrying capacity of the lake. He can also snorkel it to check the quality of the water and see what the bottom is like.

The other thing I would do tend to the shoreline to develop the riparian areas, this might relieve some of the nutrient overload and help with the algae, and would probably do so within a short year or two to start.

We have many natural lakes in our area that are basically the same as his and mine that support natural fish and have for decades with no aeration, spring fed and shallow, little beauties. Please go feed the fish in one of them and see how that changes things. Your lakes up there have a low nutrient load in them, which is completely different than his.

I have aerated in the winter to keep my ice open for my trout but Ill have inflow/outflow this winter so I wont be aerating.

Cheers.

Toby - Have you tested for DO and temperature in the areas near the spring water inflows??.
Do the springs have dissolved oxygen when they enter the pond?
Do the springs enter the pond from underground or drain into the pond above the surface?
I don' think your aerators are affecting very much the pond zones in the areas marked on the map as 7' and 9'. Next time at the pond make DO/temp measurements at the bottom at 7ft, 8ft and 9ft areas.
Questions:
1. Do you have a secchi disk or white bucket lid or white coffee cup you can lower into the pond to determine the depth the object no longer visible??.
2. for a 3/4 hp compressor - What brand and model is it? Do you have a good pressure gauge (30psi) on the comperssor?
3. What brand of diffusers do you have? .
Aeration done correctly can maintain dissolved oxygen on the bottom. Amount of DO on the bottom depends on the type of aeration, size of the aerator/diffusers and how long it is run. If one wants DO always on the bottom for adequate aerobic bacterial decompositon and lack of hydrogen sulfide buildup then the bottom water has to be routinely replaced when DO is less than 1.0 ppm (mg/L) on the surface sediment.

Tinylake has some good points for a pond that is not aerated especialy if the pond receives underground springwater. Goals determine the benefits or need of aeration. One can grow fish in a pond without aeration. Fish can survive better in low DO water when the water has lower temperature and fish metabolism is lower. Lower the water temp the less DO they need to survive. It also fish specie dependant.

I have tested in the spring that runs up top. It has about a 40ft creek as it run into pond. Levels were under 3 mg/L. Doesn’t seem like it. One up top and one listed in pic above as “Under water spring”
1 – I am sure I can do something and report back
2 & 3 – I just did Amazon thing. I thought by the amount of water being moved visually, it was plenty. Here is the link https://www.amazon.com/dp/B0DLWC1WNJ?ref=ppx_yo2ov_dt_b_fed_asin_title

I'll be back out there next weekend. I'm thinking about moving A1 towards deep end. I originally didnt because i was trying to oxygenate water as it came in by the main spring(top side one)

Move it out to 7'-8' water depth.

I looked at the link you posted for the system. I have to think that they are pulling those specs for the psi/cfm out of their hind end. Here's why.

Typically max cfm readings are done at 0 psi backpressure. They are saying that the compressor produces a max of 5.76 CFM and then their spec says that is at 16' water depth or 6.9 spi. They go on to say that the compressor produces 3.87 CFM @ 49 feet and 1.98cfm at 229.6 feet of water depth.

I find that really, really hard to believe. A 3/4 hp Brookwood rocking piston compressor from Vertex produces 5.6 cfm at 0 psi, Here are the other psi/cfm specs:
SYSTEM HF 2,3,3+
VOLTAGE 115 Volt

PSI CFM
5 5.22
10 5.10
15 4.93
20 4.73
25 4.55
30 4.34

The Vertex compressor is only rated to 30 psi or abnormal wear will occur.

Those compressors are very likely foreign made, probably china or ???.. The main thing Iwould be concerned about is where to get rebuild kits. Cheap foreign compressors for pond use may only last 1-3 years before a rebuild of the diaphragm cups are necessary depending on hours of use and depth of water for the diffusers. Do not expect to get 5-6 years of use from this brand of foreign low cost compressor. Good compressors well cared for with rebuilds should last 20-40 years. My GAST is 25 years so far on all original parts. Motor Bearings should last for 3 rebuilds.

With 3ppm DO spring water entering the pond, I would not be concerned with special aeration of this water because the dilution factor as spring water enters the pond will fairly quickly mediate the impact of low DO of the incoming spring water.

Brookwood rocking piston compressors are US Made by either Thomas or Gast.

Learn about Secchi disk or similar all white disk and use it. I will inform you about what the depth readings mean.

I agree with esshup get some current DO readings near the bottom (within 6"-10" of sediment) on a lateral transect from depths of 6, 7, 8, 9 and 10 ft moving from current T1 diffuser toward the T2 diffuser. This information will help with replacement of the T1 diffuser.

Sorry, i posted in haste last night to the one i had going about algae. I meant to post here about DO. I took some depths and moved the Diff 1 deeper. I'm going away later this week, off to Baja for a week chasing tuna so i'll test DO and clarity when i get back. Hopefully i can test some change in DO beyond 8ft deep by then.

I'd move the white one to the tip or the center of the 12' deep area closest to the spillway, and move the black one much closer to the upper tip of the 8' deep area nearest the top spring side of the pond. Then sue the ball valves to equal out the boil coming to the surface from the two diffusers.

I agree with diffuser placement as noted by esshup. Run it next year 2026 and compare temps and DO measued in August 2026 with those in 2025.

Looks like great suggestions. I was leaning that way. Had placed the diffusers before taking these last measurements. I'll move them when i get back and try to take a visibility test as well and report back.