Editor's note: We received this question from a recent customer and thought we would share it with all our readers - as well as the answer!
Question: I just bought a house and there is a 1/3-acre pond located on the property. Most of it is covered with green, slimy stuff. The rest of it has this dense green vegetation growing up in it. Around the edges of the pond there are cattails everywhere.
I’ve seen pictures of this pond from 30 years ago and it was a beautiful, clear-watered pond that invited you to come in swimming. The previous owner said it was 10’ deep in the middle when it was built. Now it is only 6’ in the deepest area. The previous owner said that when the seaweed (submerged aquatic plants) and the algae (green pond scum) grew, he would treat it with chemicals to kill the growth. At first it controlled the weeds for most of the summer. As time went on, however, he had to treat it for the green pond scum and seaweed more and more often.
What caused these problems and what can I do to get the pond back to its’ original beauty?
Answer: First of all, there are no silver bullets or instant fixes. Your pond didn’t get this way in one year and you won’t be able to fix it overnight. What happened is, nutrients have entered the pond water in many ways - such as through erosion run-off, fertilizers, grass clippings, leaves blowing in to the pond, nitrogen in the rain during thunder storms, mulch washing in, etc. Wherever you have water, nutrients, warm enough temperatures and sunshine, something green is going to grow. You may have some control over WHAT you grow, but you are going to grow something.
Using harsh chemicals to kill-off the algae and seaweed not only kills the algae and seaweed, but also kills the good bacteria, enzymes, desirable plant life and a lot of the biodiversity in your ponds’ ecosystem.
Every time harsh chemicals are used, there is more damage done to the pond ecosystem.
As nutrients build up in a pond, more and more algae and seaweed grow. When this vegetation dies from chemicals, winter freezing and the vegetative life cycle, it drops to the bottom of the pond - forming a layer of muck. If there is enough oxygen and good naturally occurring bacteria, the dead vegetation is broken down into a very thin layer of muck and some of it is oxidized by other bacteria and enzymes.
The problem that occurs is that there is little dissolved oxygen in the bottom of most ponds and lakes because water stratifies, or separates by temperature. What oxygen IS there is consumed by the decaying vegetation. Oxygen is dissolved into water through contact with air. Contact only occurs on the surface and because of stratification, the dissolved oxygen does not get moved to the bottom where the dead vegetation is piling up.
Over years, layers of muck build up inch after inch until there are several feet of muck. There is an old saying; "Every pond is destined to become a meadow." But what we are experiencing in this scenario being discussed, is much more rapid and much more damaging. Through the use of harsh chemicals, we have sped this process up tremendously and created cesspools in the bottoms of many of our lakes and ponds.
Due to the lack of oxygen, dead vegetation only particularly decays, leaving a thick layer of muck.
The lack of biodiversity coupled with the presence of phosphates and other nutrients, in the form of muck. greatly increases the likelihood that the pond/lake is going to grow toxic algae.
My family and I were in Indiana this summer and stopped at a State Park. While there, we learned that several of the State Park Lakes have or have had varying degrees of toxic algae!
There are however many things that can be done to improve the quality of water in our ponds and lakes. Re-establishing the health and balance in your pond’s ecosystem can be achieved by following the below steps. The main ingredients are oxygen, bacteria, enzymes, pond plants and controlling what goes into the water.
Number one is Aeration, which should probably be called “Mixing the Water” or “De-stratification." Using a true Aerator to de-stratify the water and move dissolved oxygen to the bottom of the pond or lake will help to get rid of the waste and decaying plant matter on the bottom of the pond or lake. An Aerator pumps air through weighted tubing to the bottom of the pond where a diffuser (air stone or diffuser plate) releases small air bubbles. As these bubbles rise, they push water up off the bottom. The further these bubbles rise, the less water pressure they encounter and the bubbles expand, pushing more water upwards. This is the most economical and efficient way to mix the water in a pond. Getting dissolved oxygen circulated throughout the water column will accelerate the decomposition of organic waste, get rid of toxic gases in the bottom of the pond, help clarify the water, and creates a much healthier environment for fish and other aquatic life to live and thrive within. Lake aeration systems and pond aeration systems are available from Water X Scapes.
Number two is bacteria and enzymes. Helpful lake & pond bacteria, added once a year, will start to consume sludge and muck. Adding lake & pond enzymes once to eight times a year will increase the effectiveness of the bacteria by as much as 3 times. There are also muck eraser pellets and packets to concentrate the helpful bacteria in specific areas such as swimming areas and along the shore.
Number three is to control what goes into the pond, if possible, to begin with. Don’t fertilize your lawn within 10’ to 20’ depending on the slope of the bank. One of the ingredients in fertilizer is phosphate. This nutrient really stimulates algae growth. Phosphates can be tested for and a phosphate binder can be added to help with this problem. Blow grass clippings away from ponds edge and keep the lawn mowed higher around the pond to keep leaves and debris out.
If there is a stream source or storm water going into the pond, it is often possible to dig a settling area called a sediment forebay (see diagram below) between the pond and the stream, in order to allow dirt and debris to settle-out in this area before going into the main body of water. This area can be re-dug or cleaned out easily if and when it fills up with gravel, sand and other solids.
Number four is that any time you can use pond plants to remove nutrients out of the water, you are improving the water quality and thus the ecosystem. Adding a stream or pond area with plenty of aquatic pond plants to filter the pond water can have major benefits. Pumping pond water through a bog filter area allows aquatic plants to remove or consume the nutrients suspended in the water. Then, remember to remove vegetation in the fall.
Add aquatic plants, if practical, between the sediment forebay and the pond to filter out nutrients. A “plant bog” (see diagram below) will help to settle-out solids and remove nutrients before they get into the main body of water. Aquatic plants such as Marsh Marigolds and Japanese Irises generally thrive in these situations and remove a tremendous amount of nutrients. The tops of these plants should be cut off in the fall to remove the stored nutrients in the green foliage before it dies and the nutrients is released back into the pond by decaying.
By using Aeration, you will start the process of getting rid of sludge and muck on the bottom of your pond. By adding one or more of the following - Bacteria, Enzymes, Muck Pellets or plants - you will speed-up this cleaning process by as much as three times. During this process, less and less seaweed and algae will grow. Water will become clearer and more inviting. Remember - your pond did not get to where it is now in one year, so don’t expect it to fully recover in a year. But you will be surprised how nicely it can recover in a couple of years with some effort and attention!