Anyone who has spent any time near a pond or lake knows that water seems to attract debris like a flytrap attracts flies. The pond or lake is always the low spot, so as the wind blows and swirls debris, it ends up in the low spot. When that debris touches the water, it is stuck and will eventually sink to the bottom.
This is the story of a pond or lake’s lifecycle. They are all slowly filling up with debris. The less water movement there is, the less oxygen there is, and the more quickly they fill unless the body of water has sufficient oxygen and bacteria down low in the bottom, which will break down all of the debris.
The muck on the bottom of your pond is your water’s primary source of nutrients. It is generally a combination of animal waste, plant debris, leaves, lawn clippings, sticks, and whatever else falls into your pond. Muck is the soft, stinky stuff that your feet sink into when you try to walk into a lake or pond. This muck makes your walk in the water a bit less enjoyable and stores a great deal of excess nitrogen and phosphorus that acts as fertilizer for pond algae. If the muck gets too thick and too rich in nutrients, it will reduce water quality and clarity and possibly create a toxic environment for fish or other organisms. Fortunately, muck can be treated, and the water body’s health can be restored.
We will discuss the most effective ways of dealing with this stinky muck that is choking our ponds and lakes.
A healthy, low-nutrient pond bottom is relatively firm and consists of primarily inorganic silt, sand, and gravel. This type of bottom will not add additional nutrients to your water.
Muck Treatments
Physical Removal
Dredging is the most straightforward and logical way to get rid of muck. Whether by hand or using large equipment, physically removing the muck can undoubtedly solve the problem of high nutrient levels in our bodies of water. Unfortunately, whether you do it manually or mechanically, it is a great deal of work and can get quite expensive. We can remove muck with shovels and rakes the old-fashioned way in a small pond, but as the body of water gets bigger, our options become limited to using long-reach excavators or draglines to reach as far into the pond or lake as we can from the shore, or we can put these excavators on large barges and reach down to the bottom to pull up the muck. Another option is hydraulic removal, which is typically people wearing scuba gear, diving to the bottom, and sucking out a slurry of muck and water using suction pumps. Any of these options will work, but none are easy. Even if you have the energy and the money to dredge your pond, the next question becomes, “What do I do with all of this stinky muck?” We either need to pay to have it hauled away or spread it somewhere on-site and wait many months for it to dry out. You will want to place this muck far enough away from the body of water that a big rainstorm isn’t going to wash it back into the water.
Be aware that in an old, muck-filled pond or lake, this dredging activity can stir up so much debris and nutrients that it can cause fish kills in extreme cases. Also, some of the phosphorous and nitrogen in the muck will get mixed into the water column, which may cause a quick algae bloom soon after the dredging.
Decomposition
Just like your greens, lawn clippings, leaves, etc., will eventually decompose in your backyard composter, the accumulated muck and debris on your pond bottom can also decompose. On dry land, the leaves and debris break down and turn into rich soil, which gives up its nutrients to the plants growing in the soil. This process works very efficiently because of the many plants growing in the soil and because plentiful oxygen and bacteria are present to help facilitate the breakdown.
Our pond bottom is a very different place. We typically don’t have plants growing to pull out nutrients on the bottom, and we don’t have much oxygen or bacteria at the bottom, either. The lack of these three things means that anything that falls into your pond is very slow to decompose. If only our pond or lake bottom could have everything it needs to allow the debris to decompose more quickly.
We do our share of physical muck removal from ponds, but when the body of water becomes so large that an excavator can’t reach across it, the best way to get rid of the muck is to give the pond bottom everything it needs to decompose it.
This leads us to an easy method of muck removal. While this method is not quick, it can certainly take years; it is relatively painless and easy to implement.
We said that the pond bottom is short on oxygen and bacteria. Well, let’s fix that problem.
Specialized Equipment
Specialized equipment such as bottom diffusers, bubble tubing, surface aerators, fountains, and now oxygen saturation units can add dissolved oxygen to the water column and the muck layer’s surface. Typically, your pond bottom will only have anaerobic bacteria in the muck. This type of bacteria doesn’t need much oxygen and works well but very slowly. This anaerobic bacterial activity is what makes the muck so stinky when we stir it up and release the carbon dioxide and hydrogen sulfide.
The more dissolved oxygen we can add to the muck layer, the more favorable the environment is for aerobic bacteria, which need oxygen to survive. These aerobic bacteria can work much more quickly than their anaerobic counterparts, and they love to digest the organic debris. Breaking down organic compounds found in muck using aerobic bacteria is better than anaerobic digestion because it happens much more quickly and does not generate toxic compounds such as methane or sulfur. Stimulating the natural aerobic bacterial community reduces nitrogen and minimizes phosphorus release from the muck layer by creating an aerobic zone at the water-sediment interface. Aeration isn’t cheap to install, and different systems are more effective than others.
Fountains and aeration mixing pumps
The floating fountains and mixing pumps that you have likely seen in ponds and lakes certainly do their part in oxygenating our water, but systems such as these typically only mix and aerate the top 4’-6′, so in a deeper pond, we aren’t helping to eliminate that bottom muck.
Air pumps and diffusers
Having an air pump on the shore that pushes air through a weighted tube down to a diffuser at the pond’s bottom is an effective way to get oxygen down low in the pond. It is essential to understand that these aeration units have limitations on how wide the oxygenation effect is because the air bubbles quickly rise to the surface. Deeper ponds benefit more from these diffused aeration systems. The action of the bubbles rising to the surface will turn the water column, which leads to de-stratification. Over time, these bottom diffusers increase oxygen levels down low. Still, it is important to spread out several diffusers throughout the pond to ensure we get sufficient oxygenation throughout.
Oxygen Saturation Technology
This new system for oxygenating the pond bottom is much more effective than any of the techniques mentioned above. However, it is also much more costly and requires a 220-volt service near the pond. This new technology disperses much finer bubbles that spread across the pond bottom and stay there, which is the ultimate oxygenation for a pond bottom. I believe technology such as this will revolutionize the pond and lake treatment industry and likely eliminate the need for costly and destructive chemicals over time.
Once we have sufficient oxygen down low in the pond, we can start adding a diverse dose of fast-working aerobic bacteria to the water. By adding high doses of bacteria to the water, we are simply speeding up the decomposition process of the muck. We will usually use sinking bacterial tablets so that the bacteria gets right down into the muck layers and can begin to work immediately.
Give bacteria a home
The other thing we can do once we have good oxygen levels deep in our ponds is give this aerobic bacteria an excellent place to grow and colonize. We can install BioBoost Nests deep in the pond near our aeration units. These nest units can be thought of as hotels for bacteria. Each unit has a ton of surface area to allow maximum bacterial growth. Bacteria need surface area to survive, so by dramatically increasing the surface area near the bottom of our lakes or ponds, we can dramatically improve the effectiveness of our bacterial treatments.
The Muck Busting Combo
This three-way combination of aeration, bacteria, and a place for the bacteria to live will significantly speed up the decomposition of any organic debris on the pond bottom. Ponds and lakes, if adequately treated, can lose inches of bottom muck per season. As these muck layers are broken down and eliminated, the nutrient levels in the body of water will drop dramatically, and algae problems will be significantly reduced. Less muck equals better water quality and happier people.