Considering the fact that I have a Bachelor’s Degree in Natural Science education, this has got to be my favorite article.  I love to spend my extra time learning more about pond ecology. This is the basis of all ponds. If the ecological balance isn’t maintained, then fish and plants soon begin to die. Once ecological balance is established, bar any major disasters, it is usually easy to maintain.

As us “land creatures” are ruled by a big cycle of events we call the food chain, so is the world of water gardening. The first stage of the pond food chain is the microorganism of algae, plankton, and microscopic plants. Insects such as flies, bugs, and worms feed upon these substances. Fish then devour the plants and animals from the first and second stages of the food chain. The total ecological balance of the pond relies on this chain. If this chain is broken, disaster occurs in the form on pollutants that can kill the fish and plants.

Nutrients and chemical elements in the water consist of carbon dioxide, oxygen, phosphorus, and nitrogen. Trace elements also occur in minute amounts. The pace at which these elements are created and discharged into the water is controlled by time of year, amount of sunlight, and environmental system. In the desert and southern United States, we get more sunlight than other regions. This can amplify our problems of algae and unwanted decomposed elements.

Aquatic microbes and fungi that are largely found in the muddy bottom of ponds, where dead plants and animals can accumulate, can cause unwanted pollution. Decomposition can occur rapidly; therefore, allowing pathogenic (disease causing) organisms to rapidly increase in your microclimate called a water garden.

The exchange of carbon dioxide (CO₂) and Oxygen (O₂) are the basic elements for the respiratory cycle of a pond. Plants absorb the CO₂ and provide O₂. This process is commonly termed, photosynthesis. How does this occur? Plants take in the carbon dioxide (CO₂) and by diffusion mixes it intercellular water (H₂O). This forms glucose (C₆H₁₂O₆), which is energy for the plant. The “left over” oxygen is then released into the pond.

The amount of oxygen released into the pond also depends on the water temperature (cold water retains more oxygen), the movement of water, and the quantity of decomposing material, which will decrease the oxygen levels related to decomposing substances that uses up the oxygen. For this reason, an added fountain or waterfall greatly increases the oxygen level in your pond. Decreasing the decomposed muck in the bottom of the pond also increases your oxygen levels. Both are extremely important in warm weather climates.

Plants and animals that die in water sink to the bottom. Extra food not eaten and fish excretion also ends up in the bottom of the pond. The decomposing of all these substances can lead to a toxic situation in your pond. Bacteria in the bottom convert these substances into nitrogen, which is released into the water. When nitrogen (N₃) combines with the hydrogen molecule (H) in water, it forms ammonia (NH₃). Ammonia can help your plants grow, but too much ammonia is detrimental to your pond. The ammonia replace the oxygen content; therefore, causing plants and animals to perish.

Snails are very important to this cycle of pond life, because they feed upon the dead organisms and prevent the production of ammonia. Snails have a very high tolerance for ammonia. When they start to die, this is a grave marker of the toxic intensity of ammonia in your pond (they are on the bottom where the ammonia levels are highest).

Nitrogen and phosphorus enters the pond through water changes and decomposition. This is the basis of limiting the amount of fish food to only what the fish will eat in five to ten minutes, and adding water in small increments.

Careful balance of elements is accomplished also by proper maintenance with biological and mechanical filters. A biological filter can be as simple as a rubber/plastic trashcan with a screen, filter material (or quilt batting), lava rock, and floating plants. The biological filter makes life tougher for algae by changing the nitrogen and phosphorus levels. The size of biological filter depends on the size of your pond. It should hold up to 10% of the total size of your pond. A 1500-gallon pond would require a biological filter no less than 150 gallons.

The mechanical filter filters out tiny particles and decomposed plants and animals in the pond. It may be even necessary to attach a vacuum to the mechanical filter once a month to deter the accumulation of decomposed material at the bottom of the pond. The mechanical filter is measured by gallons per hour, and should be able to circulate the pond in two hours; therefore, a 1500-gallon pond would require a mechanical filter of 750 gph.

Light affects these microbes by increasing the process of photosynthesis. During this process, food the sunlight is converted to energy by utilizing chlorophyll, which is the “green” in plants. This stored energy is needed for animals and plants to survive.

Algae growth can be very destructive because it will impede the light from entering into the water; therefore, plants cannot undergo photosynthesis to make new food. No energy, means no plant. No plants, mean no animals.

Temperature doesn’t affect plants as much as it does the animals of our microclimate. Any change in temperature also changes the amount of elements in your water, especially oxygen. With an enormous change in temperature, fish and snails that are affected by the change, seek stabilization by moving to the bottom of the pond. Most freshwater fish can adapt to extremes such as freezing in the winter and scorching temps in the desert heat without great distress. Tropical fish and plants have a much harder time, and must be protected from immense variations in surroundings.

The amount of oxygen, hydrogen, nitrogen, and phosphorus in a pond also is the controlling mechanisms of the pH level of the pond. The pH level should range from 7.0 to 8.0 to reduce the production of algae. It can be measured easily with simple test kits. In fact, I use the same pH kit for my pond and pool. NEVER empty the testing water back into the pond. Levels should be checked once a month. I always check mine a few days after my once a month fertilizing of plants.

The pH problems can be treated with home “solutions” of baking soda or vinegar, or by using commercially produced pH modifiers. For a pH lower then 7.0 used ½ cup of dissolved baking soda to every 1000 gallons. Using 1 cup of white vinegar for every 1000 gallons can modify a pH higher an 8.0. After adjusting the pH, test the next day at the same time, since pH levels will fluctuate during day and night time hours. The most appropriate time to check levels is mid-morning.