Pond Boss Forums AERATION Should I aerate? Aeration for 20+ acre pond 7' deep and less

We have a 20+ acre natural pond that averages around 7' deep and doesn't have a dam. It's mostly shallower than that and is an oval shape (sort of a bowl so to speak). It's located in South Alabama and water fluctuates around 2' during the year - mainly summer as there are no streams feeding the pond and only the surrounding watershed runoff supplies the water. A massive fish kill occurs every 3-4 yrs, and I'm wondering if there is an aeration system to consider. A large water well has been used in the past to maintain the water level so it doesn't drop during the summer to the tune of 2' mentioned earlier. I believe the oxygen supply from the water well helped but lightening strikes have deterred our enthusiasm to continue to replace the pump. I welcome any thoughts on whether or not an aeration system could help with the fish kills given the depth of the pond. Aeration may also help remove muck and increase depth if I had to guess since the bottom is very soft. Thanks in advance for any input!

Tom, it all depends on your budget for the project. I've been working with a Homeowners Association that has a 19 ac pond that is roughly the same depth as yours. When it is all said and done, the aeration system will be a combination of bottom diffusion aerators and surface agitators.

It is unlikely that your well water is adding any oxygen to the water at all. Well water is usually devoid of oxygen when it exits the ground. The additional water volume may add to the total oxygen capacity of the body of water, but only after it has properly equilibrated.

Some pond boss members have special set ups to oxygenate the well water before it is added to the pond.

Tom, considering REGIONAL aspects. I am in total agreement with Scott (esshup).
Scott manages northern ponds and has freezing temps with ice to contend with. My experience is with Texas ponds with heat and drought to contend with.

In our shallow Texas ponds less than 7-8 ft deep, IMO bottom difffusr membrane systems have a high probability for fish kills, whereas surface aerators introduce max O2 and offer protection against disaster.

From reading northern forum reports, bottom diffuser membrane aerations offer maximum protection for iced over northern ponds, providing O2 in thawed areas.

I have learned from success and failure about aeration in small Texas ponds, as well as to observing how Overton Fisheries handle their aeration on grow-out ponds and hatchery/brood ponds.
I may not be correct, but I believe Todd has removed bottom diffuser systems from hatchery/brood ponds and aerates with tractor mounted paddle wheels devises. In his grow out fishing ponds, I see surface agitators.

I only report on my experience and failures on small ponds so would not try to address best O2 management on a large 20 acres lake.
Based on my experience in Texas hot/drought conditions, bottom diffuser systems in ponds less than 7-8 feet is a waste of money and invitation to fish kills - IMO.

Best of luck
George Glazener

George, you are correct to a certain extent. Bottom diffuser aeration system swill work at shallower depths for warmer water, Texas ponds, but it's more critical to look at the GPM of water moved to the surface in shallower applications. That typically requires more diffusers per surface acre than what is spec'd. out for a deeper pond, which means more self-sink air line, which drives up the cost.

In hatchery ponds where they are seined out, having the diffusers on the bottom makes it hard to seine, and more labor is involved because I'd imagine that they'd have to be removed for every seining.

I don't know where the break even point (operating cost and system cost) is for surface agitators vs. bottom diffusion systems, but for shallow production ponds, what Todd is using IS the best for his application, no doubt about it.

Surface agitators and paddlewheels will transfer a lot of O2 to the water, but what are the operating costs, and what are the maintenance costs per "X" amount of O2 transferred? I don't know the answer to that question.

It's all about overhead costs in a hatchery, so I believe that the surface agitators and paddle wheel aerators transfer more O2 to the pond AND are easier to remove for seining than bottom diffusion systems.

I have a clients pond that has a high BOD due to 5' of muck in the bottom of the pond, many leaves falling into the pond and possibly mound type septic systems dumping water into the pond. The pond is 5/8 acre and 7' deep max. Running 3 Vertex XL4 diffuser stations, and one Kasco surface agitator, the O2 levels were at saturation in 79°F water temp top to bottom in the water column in all depths of the pond, and the Rainbow Trout were still alive. Could I do that with just a bottom diffuser system? I doubt it. Could I do that with multiple surface agitator without a drop tube on at least one of them? I doubt that as well, but a phone call to Kasco or Otterbine should get an answer relatively quickly.

The other thing to consider is the cost of the power cord. In that 19 ac pond, I ran approximately 1 mile of self-weighted air tubing. Some runs were over 800' long. That was just for half of the pond. What would a power cord that length for a surface agitator with a 1 or 2 hp motor cost??

Scott my friend, you have spent an awful lot of time telling me about a lot of stuff I already know.

I learn from observation as well as experience, having been around one of most sucessful, large scale hatchery operations in this part of the country - as well as sucessfully managing our own ponds.

I speak only from personal experience and fortunate not having to put groceries on the table by managing ponds and selling stuff.
I admire and respect you guys in the fish business.
I have been learning from my mistakes since before Pond Boss was a forum.

Have fun.
George

ps: Scott, nearly forgot - is there a text book on the "Law of Diminishing Return" - some folks need to read it!...

George, I am curious as to Texas ponds and muck build up. I was under the assumption that the bottom diffusers help break down muck. When a pond is in that 6 to 7 depth, does the surface agitator bring enough O2 down to that level to help with muck.

I know that this doesn't really help Tom's problem, although we all don't want are ponds to fill in needlessly, but just curious if southern ponds don't have to worry about muck build up as much as northern ponds.

Current price for submersible cable to run a 2hp (230V) motor at the end of an 800' run is about $3K - and I think the prices are down a bit right now.

George, I think we are saying the same thing, just saying it in different words.

Heck, I gotta check your memory on occasion!

Good question Fish…The best answer I can come up with is what percentage of that muck can be handled by O2, tilapia, and bacteria, and how much and how much silt?

OR - and I don’t like this approach …Drain - Nuke - Doze…?
IMO each should be considered on a case by case basis by a competent fisheries biologist.

I would say all ponds will have muck problems over time due to siltation and organic matter - we don’t have any trees near out ponds.

I had some three years misadventures with our pond before PondBoss began.
Never heard of aeration until PB and then only wanted it because I was advised I could double carrying capacity - BIG mistake!

I know several well managed Texas ponds with NO aeration.

I first joined PB in 2002 - long before the current generation of PB members and still on steep alearning curve.

“ I was under the assumption that the bottom diffusers help break down muck. When a pond is in that 6 to 7 depth, does the surface agitator bring enough O2 down to that level to help with muck.”

The reason I am adding the 12 v ¼ hp surface aerator to our small sediment pond is to add Max O2, hopefully to cure fertility problem that becomes a stagnate puddle during low water drought conditions.
Water bottom under 110v 1hp Kasco surface aerator is clean, giving me the impression is that it that it provides good circulation as well as adding max O2.

Perhaps others can better answer your question - I am fortunate to just pick up the phone and call Todd when serious info is needed.

Best,
George

I have one of the 230v surface aerators and 300' of line in my 3 acre pond. It creates ripples over the entire pond surface with no problem.

I have to use surface aeration because my pond has geothermal tubing in the bottom, but I think the shallow nature of your pond would benefit greatly from one or maybe two them. The surface aerators move a great deal of frothy water compared to my 220v 1.5 hp pool pump that runs a fountain in the pond. That's like a squirt gun compared to 3' long super soaker in a water fight. Absolutely no comparison.

Here's a picture of the Tasco 230v surface aerator with 300' extension. It's only out about 250' worth though. As you can see, it pretty much fills the entire 3 acre pond with waves. FWIW, once you get a lot of surface crap off the pond: algae, lillys, weeds, etc, it fills the pond with bigger waves.

My 1hp 110v Kasco surface aerator throws a much better "ripple" effect than my bottom diffusers, as your does.
Why does this not pick up O2 from water/air interface as well or better than bottom diffuser systems?
Below is a good example and comparison of the two systems performance on a 2 acre pond,

Another thing with the surface aerators; they seem to disperse chemicals a lot more efficiently too. Wouldn't seem like they would, but even putting copper sulfate in the front part of the pond the aerator dispersed it to the bigger side of the pond and killed the algae there within a day. No fish kills at all either.

Wouldn't the more aggressive "boil" actually lend itself to faster evaporation?

Could it be due to the pressures involved with bottom diffusers?

If you can create ripples on the surface, you greatly increase the surface area of the pond surface. The more surface area you have the more contact you have with the sunlight and more oxygen you create.

Bottom diffuser bubbles lift the oxygen depleted bottom water to the surface and in contact with the sunlight and is thus oxygenated. The smaller the bubbles a bottom diffuser can create, the more "lift" it has.

I should probably know this, but I don't, what the % rate of bubbles goes into the water as dissolved oxygen. It's not as high as you'd think though.

In addition to quicker evaporation rates, would surface aeration heat the water faster?

That might all depend on the difference between the water temp and the ambient temp. IIRC one member here put together a packed column to degas and oxygenate well water and saw a few degree temp drop from the top to the bottom of the packed column.

Faster moving water in the surface systems....heat up quicker, even a tiny amount? Molecules are molecules!

OK, ok, then we have to take into consideration the dewpoint depression and that gets too technical for me to do in my head.

Ha! Got one on the engineer.....and it was in the math! Somewhere, Dennis is smiling.

But increased evaporation causes cooling, what now......

When water evaporates, it is going to a lesser state, therefore it cools down. So, depending on the amount of evaporation (which is dependent upon the dewpoint), THAT will determine the amount of temp drop.

So now it's up to the small engine guy to figure out a chart that states what the temp change of the pond is in relation to the water temp, ambient temp and dewpoint.

That's where my brain said TMI to figure out between these ears.........

So by virtue of evaporation, surface aeration gives us cooler water but less water overall remains in the pond, when compared to bottom aeration? (higher evap. rate)

So extrapolating even further and thinner, surface aeration in a drought ridden area where every drop counts, will contribute to daily water loss to a greater degree than bottom aeration will?