Improving Pond Water Quality

By Chris Beberg, Andover, MN Originaly published in Passion For Water, Spring 2009 Revised Spring 2014

Water gardening is a very enjoyable hobby, and for many a true passion. The pleasure of experiencing the many life forms and natural elements existing together in harmony is never ending. Water gardens are rich with colors, are powerful with motion and are pleasing with sound. Unfortunately, features that are designed or built improperly may be rich with green algae, or powerful, obnoxious odors.

Success with controlling water quality in a pond or other water feature can be easily attained. The key is to understand the basic activities that happen day in and day out in your pond. The enjoyment of water gardening can be greatly enhanced by recognizing why natural processes occur in your pond and having the ability to correct a problem if it should arise.

A water feature designed and built to balance the natural ecosystem is the most environmentally sound method of developing good water quality. This is based on creating a balance between the nutrient consuming beneficial bacteria and the amount of nutrients dissolved or accumulating in the water. To achieve this balance, we simply take steps to ensure good counts of bacteria develop.

Aerobic bacteria are beneficial microorganisms that consume dissolved nutrients in the water. These bacteria are naturally present in larger, healthy bodies of water such as your favorite swimming lake. As with all living creatures, creating a supportive habitat for them increases their number, and thus the effectiveness of cleaning the pond. Culturing high numbers of aerobic bacteria will keep algae from having food to grow on and will keep noxious phosphorous odors from developing. Bacteria need only a few things to grow rapidly: a surface to live on, dissolved oxygen in the water to process their food, and a stable pH as close to neutral (7.0) as possible. When these factors are present, we simply need to add good quality pond bacteria to get the process started.


Bacteria need a surface to live on. The more surface space available, the more potential for bacteria growth. Providing additional surface space is the goal of most modern biological filters such as the EasyPro AquaFalls. The AquaFalls acts as your waterfall base or stream start, and provides the place where high levels of biological filtration occur.

The AquaFalls is “supercharged” by adding biological filter media in addition to the filter pads. The biological media is material that has tremendous surface area allowing the bacteria to culture and grow in your filter system. It is placed in the mesh bags provided with the filter and sandwiched between the filter pads when placed in the AquaFalls box. EasyPro makes several types of biological media, which will last the lifetime of the pond: Bio-Balls, Filter Floss Media, Bio-Blox, and Ultimate Bio-Media.

The construction technique of covering all surface areas with gravel is also helpful in adding surface area. The smaller the pond, the more critical it is to have additional surface media in the filter.


Aerobic bacteria need dissolved oxygen to live and metabolize nutrients. Without dissolved oxygen, aerobic bacteria will die and you may develop green toxic water. Anaerobic bacteria require much less oxygen to work and will often be present when aerobic bacteria are not, but aerobic bacteria are proven to be seven times faster at breaking down organic nutrients and turning them into non-organics.

Dissolved oxygen is often the foremost consideration in developing good water quality through bacteria culturing. This is the reason that a well circulated or aerated water feature looks clean and smells fresh, not foul. The level of dissolved oxygen can be increased by adding an additional waterfall, aeration system, circulation pump or fountain feature.

Water has a limited capacity to hold dissolved oxygen. As water warms during the summer, the ability of water to hold dissolved oxygen falls. So in addition to using circulation to add oxygen, care should be taken to reduce heating of the water. Plants may be the best and easiest way to keep water temperatures in check by offering shade.

For those who want to use an oxygen meter, you can expect about 11 parts per million of dissolved oxygen at 52ºF. As the water warms to only 80ºF, the level will fall to around 8 PPM. When the level falls to 3 or 4 PPM, additional negative effects occur including fish die off, noxious odors, nutrient build up, sludge accumulation and chemical imbalance. As a rule of thumb, any foul smelling water can be assumed to be low in oxygen.


A stable pH is critical to maintaining and culturing beneficial aerobic bacteria. It has been found that ponds with a pH of around 9 or higher have very little chance of aerobic bacteria surviving. Maintaining a pH of 7.5 to 8 is ideal.

Good pH management starts with selecting stone for your pond that does not change the pH. Check with your local stone supplier about pH impact before selecting your stone type. Typically more dense rock such as trap rock, quartz and granite will not change the pH, while most limestone will cause a detrimental increase. Additionally, water being added from a well or municipal source may be high in pH.

If high pH is a problem, use regular testing to determine how much EasyPro pH Down or EasyPro pH Up to add. It is very helpful to use water buffers when changing your pH to eliminate wide swings in pH levels which can be very stressful on fish. Always make small pH adjustments; do not try to correct it all in one day.

If the water in your feature has high dissolved oxygen and the pH is stable and near neutral, you typically are ready for culturing bacteria. Bacteria colonies are more rapidly developed when we start them by adding EasyPro’s All Season Liquid Bacteria. This liquid pond bacteria contains a unique formulation of bacteria that will remain effective in a wider variety of water temperatures, making it a single product solution. Now that’s Easy! When adding bacteria to a new pond, or when adding significant amounts of water to refill an existing pond, it is helpful to use a chlorine, chloramine and heavy metal remover like EasyPro Water Conditioner. Chlorine or chloramines are often present in municipal water sources and can be detrimental to the beneficial bacteria.

If your pond suffers from accumulated “sludge” or debris on the bottom, you can expedite the natural cleaning process with EasyPro Sludge Remover. This product is available in a powder or tablet form for easy application. Sludge Remover has bacteria and enzymes that are superior at quickly breaking down dead organic accumulations and processing the excess nutrients out of the water.


Understanding how bacteria work within the ecosystem is the key to keeping clean water in your pond or water garden. A good quality pond bacteria introduced to a water feature that has adequate surface area, a good amount of dissolved oxygen, and a stable pH is a sure bet for clean and odor free water. Happy ponding!

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