Pond Boss Forums AERATION Should I aerate? Should I Aerate a 50 yr. old pond?

I have been reading about aeration alot on this site and can't find any post that is specific to my problem.

I have a 50+ yr old one acre pond.it is about 8ft deep at the deepest point. It is fed by 2 small mountain streams and the water is crystal clear. I would like to but some fish in the pond and add a small dock and use it for swimming. The problem is that over the years the organic matter ( mostly leaves) has filled the bottom with about 2 ft. of muck and sediment.

I have looked into the organic enzymes that eat the muck but that is out of the question , way too expensive for me.
So, I was thinking about aeration. The problem I have heard about with an older pond like this one is that aeration will make the water a muddy mess and could possibly screw up the pond by mixing up the sediment and muck to a point where it is unuseable. Any thoughts on this ? Or, any thoughts on how I can get rid of this bottom muck without draining the pond?

Properly sized and operated aeration is the most $ efficient way to reduce organic sedmient over time. Mechanical removal is usually difficult to impossible (depending on pond size and the surrounding terrain) and costs more than many of us like to think about.

If the air release device (membrane diffuser, usually) is mounted on something to keep it off the bottom, out of contact with the organic debris and sediment, it shouldn't cause any cloudiness from suspension of said debris. We recently talked about such mounts in this thread, which included my DIY membrane mount.

The key phrase here is "Properly sized and operated". Aeration is a great tool to reduce muck and for certain algae control. However, improperly sized and especially improperly operated aeration can be death to your fish. This site is full of examples of people who designed their own aeration, or put in a proper system but operated it in such a way to cause water quality issues.

Your best bet is to contact one of the many advertisers and contributors to this site who design, sell and install systems. Even if you chose to install it yourself make sure you know exactly what you are doing.

Bing

Thanks for the advice fellas. My water is crystal clear right now and I do not want to do anything to change that. I just want the muck gone so we can go swimming without standing in all the muck.

KTM: Crystal Clear is an appropriate goal if you are looking for swimming or other non-fishing, non-aquatic wildlife activities. It is not what those who are primarily into fishing, etc are trying to achieve. You will likely need some truly professional opinions on aeration and other options in order to clear up the muck without creating a more fertile appearing water.

Bing

Bing,

That is why I posted the question here, for the professional opinions!

KTM, if possible, you should check your dissolved oxygen (DO)levels at the bottom of your pond before purchasing an aeration system. If your DO is already above 3 PPM (mg/L) at the bottom, aeration probably won't do much more to reduce organic sudge. It will improve fish habitat and generally improve the ecosystem though.

In general, we suggest that a sub-surface aeration system will reduce about 1" per year of organic sediment. Actually it's not the aeration system that's reducing it, it's the change in the biochemistry as a result of the aeration...but that's a different story. On the other hand, a bacteria program can consume 1" per week assuming your DO levels are above 2 PPM.

How do I check for DO levels?

I looked into a bacteria program and for my pond it was going to run me around $2,500 !!! A bit more than I want to put into it.. ( actually alot more) I thought aeration was necessary in order to have a sucessful bacteria system? The only reason I was looking to aerate was so the natural bacteria could do its thing and from what I understand the only way that is possible is if there is plenty of oxygen in the water for the bacteria to live... Correct?

Bacteria is thriving in your muck. Anaerobic bacteria thrives in the abcense of oxygen and decays organics VERY slowly, while aerobic bacteria thives IN the presense of oxygen and breaks down organics exponentially faster than anaerobic.

If you want to clear the muck rapidly (possibly all this year), spring for the bacteria AND aeration. The bacteria will get rid of the muck, assuming it actually IS organic, and the aeration will not only speed the whole process, but maintain it for many ears to come.

If the "Muck" is actually silt, well................you may need to learn to love playing in the mud!

Good post Rainman...you nailed it. KTM, DO is required for a successful bacteria program. Bottom aeration delivers DO to the bottom of your pond. If you already have good DO at the bottom of your pond, an aeration system is redundant unless you have other goals aside from sludge digestion.

I'm thinking that if your water is so clear that you can see all the way to the bottom of your pond then you probably have low BOD. This is common in high mountain lakes and ponds. If sunlight is capable of reaching all the way to the bottom of the pond then you may have some aeration via photosynthesis occuring in the bottom. Likely you have a combination of the two which would suggest a likelihood of decent oxygen levels at the bottom. Furthermore, mountain streams are generally saturated with DO and colder than your pond which means that high DO water is constantly being delivered to the bottom of your pond.

You can test DO with a DO meter. They can be kind of pricey but they are a great pond management tool. I believe that you could purchase one from one of the advertisers on this site but I'm not sure which one.

What's BOD?

Biochemical Oxygen Demand - the total demand on dissolved O2 in the pond from fish/invertebrate respiration, plants using O2 at night, and decay processes.

BOD is an actual standardized laboratory test to determine the relative oxygen requirements of wastewaters, effluents and polluted waters. The test is designed to measure the waste loadings to treatment plants and the efficiency of treatment systems. The primary oxygen consumer in the BOD test is bacterial action. The BOD laboratory test generally has little value in measuring the actual oxygen demand of surface waters and the lab results not a true representation of water body conditions since the laboratory conditions do not reproduce the actual or the real world conditions of temperature, sunlight, all biological populations in all habitats, water movement, and oxygen concentrations.

We on the PB Forum use BOD as Theo described, although it is probably not truly measureable due to the complexity of all things consuming oxygen in a pond habitat. Generally the more productive an aquatic habitat becomes the more life forms that are present to consume dissolved oxygen during the dark period.

Thanks for all the info fellas.
Water Wizard,
I went swimming in the pond this weekend and yes, I can easily see all the way to the bottom with cloudiness at all.( 5-6 ft deep)
I live on a farm in the mountains at 3,000ft. The pond is fed by two streams. I highly doubt that the bottom is silt since the pond is almost surrounded by trees, I am thinking it is mostly organic on the bottom.
So you are saying an aeration system is necessary if I want to use the bacteria ?

ktm, we still don't know if you have an adequate oxygen supply in the deeper waters. Proper aeration would ensure there is.

If you have a steady outflow of water, I would consider a bottom-draw siphon overflow system to remove the dead water. This would be a much less expensive, maintanence sp? free solution.

Adding a low catch fence would help eliminate tons of fresh leaves entering the pond as well while you get rid of the current muck.

Rainman,
Bottom draw siphon overflow system??? What is that and how does it work?

Here are a couple links. The pond dam piping system is better (and they're a supporter!)

http://www.ponddampiping.com/syphon1.html

http://extension.missouri.edu/publications/DisplayPrinterFriendlyPub.aspx?P=G1530

KTM,

What I'm saying is that you need good DO numbers at the bottom of your pond for an efficient (most bang for your buck) bacteria program. I'm not necessarily saying that you need an aeration system unless you determine that your DO levels are below 3 PPM. As Rainman stated, an adequately sized bottom laid aeration system would ensure high enough DO levels. But, if they are already high enough, an aeration system would be redundant.

Rainman, thanks for the link. I'd never seen that design before. However, I was just reading an issue of "Lake and Reservoir Management" ("Assessment of mult-year (1956-2003) hypolimnetic withdrawal from Lake Kortowskie, Poland" NALMS journal Vol 23, Issue 4, Dec 2007) which suggests that while hypolimnetic withdrawal will decrease nutrient loading, it has "little effect on dissolved oxygen in the water." One of the trends it noted is that by drawing the colder water from the bottom, you displace it with warmer water from above, which of course holds less DO. The exact opposite was true in the winter. On the other hand the study showed a decrease in the length (temporal) of summer stagnation at the bottom as well as spatial oxygen deficiencies in other parts of the lake.

Are you asleep yet? Yes, I have a full time job, newborn son, and still find time to read back issues of NALMS journals. Hey, a guy has to read something in the bathroom.