Water Quality in Ponds


What You Should Know about Water Quality in Ponds

By: Aquascape

When a pond builder puts shovel to soil, foremost on his/her mind should be the goal to create an ecosystem pond that produces superior water quality. While the customer may focus more on the design of the waterfall and type of fish and plants, it’s the pond contractor’s job to ensure that healthy water supports the life forms residing in the water garden.

Water chemistry need not be a scary topic. Quite the opposite is true. Understanding water and how it responds to environmental influences should be a basic tool in every pond professional’s belt. While fully mastering water’s intricacies can seem daunting, becoming familiar with a few key components like pH and nutrients will provide you with confidence and skills to create balanced ecosystems for your customers.

Potential of Hydrogen

A familiar term you should understand as a pond professional is pH, which stands for “potential of hydrogen.” The last time you probably heard about it was during a shampoo commercial. Essentially, pH describes the relation of hydrogen ions to hydroxyl ions on a 14-point scale. The higher the hydrogen content and the lower the hydroxyl content, the more acidic the water becomes. Conversely, the higher the hydroxyl content and the lower the hydrogen content, the more basic the water.

When the hydrogen and hydroxyl ions are in complete balance, the water is neutral. On the 14-point scale, a pH of 7 is neutral. On the same scale, numbers higher than 7 are called basic (or mistakenly, “alkaline”), while numbers lower than 7 are termed acidic.

Your typical pond falls in a pH range from 6 to 11, which covers ground from slightly acidic water to strongly basic. So for example, a pH of 8.2 is highly acceptable for pond water, while a pH of 4 (which is acidic enough to dissolve nails) would be unacceptable if your aim is to sustain aquatic life.


Many factors can influence the pH values found in water. The presence of dissolved metals and materials has perhaps the biggest affect on pond water. These substances are commonly called buffers, and are typically discussed in terms of alkalinity and hardness.

Alkalinity: When present at high levels, alkaline materials tend to hold the water’s pH at higher levels. The concentration of these buffers is expressed as parts per million (ppm).

Hardness: A specific form of alkalinity, hardness refers to the amount of dissolved calcium, calcium carbonate and magnesium in the water. Water is termed “hard” when levels of these materials reach 300 ppm or higher.

When present at higher levels, these buffering factors tend to stabilize pH. In fact, when hardness and alkalinity values are high, it’s less likely a pond will experience significant fluctuations in pH.

Aquatic Nutrition

Beyond pH, there are other contributors to water quality that must be considered, namely, the macronutrients and micronutrients that help sustain life in aquatic systems. Seventeen of these essential ingredients — three macronutrients and 14 micronutrients — need to be included in ponds and streams.


Macronutrients are what you find in commercial fertilizer mixes. For example, when you see a fertilizer that says 20-10-20, the numbers refer to the percentage (by volume) of nitrogen (N), phosphorous (P), and potassium (K) in the mix. These are the nutrients required in the largest quantities for proper plant growth.

Nitrogen: In a pond, nitrate and ammonia are the most common forms of available nitrogen. High levels of either of these substances are good for plants (especially algae) but are toxic to most fish, so it’s best if they are undetectable or held at very low levels.

Phosphorus: Again, in a pond situation it is best to have low or non-existent levels of phosphorus, which appears in the water in the form of phosphates. Although in the case of a pond, these substances are not problematic for fish, they do invite prolific algae growth and are best held at minimal levels.

Potassium: It’s rare to find high levels of potassium in pond ecosystems, but it wouldn’t be a problem in any event, because potassium is a key to both plant and fish metabolisms.

The other category you need to consider features the micronutrients. Fourteen of them are required for life: boron (B), carbon (C), calcium (Ca), chlorine (Cl), copper (Cu), iron (Fe), hydrogen (H), magnesium (Mg), manganese (Mn), molybdenum (Mo), nickel (Ni), oxygen (O), sodium (Na), sulfur (S) and zinc (Z). Each is required in different ratios for different members of a pond-based ecosystem, and each plays a highly specialized role on the cellular level for all forms of life.

A well-designed pond system will often produce water that is balanced in terms of pH and nutrient content. When algal blooms or other water-quality issues arise, don’t hesitate to seek help in determining treatment regimens that can correct the situation.

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Author: Bobby Kenyon
Bobby Kenyon is the Creative Solutions Guru for C.E. Pontz Sons who has over a decade plus experience in the Landscape & Water Garden industry . He enjoys long walks on the beach and grocery shopping but has a strong dislike for regular cake and non brand name paper towels

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